2021-01-26 20:47:25

by George Kennedy

Subject: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

During boot of kernel with CONFIG_KASAN the following KASAN false
positive failure will occur when ibft_init() reads the
ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init

The ACPI iBFT table is not allocated, and the iscsi driver uses
a pointer to it to calculate checksum, etc. KASAN complains
about this pointer with use-after-free, which this is not.

Signed-off-by: George Kennedy <[email protected]>
---
drivers/firmware/Makefile | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
index 5e013b6..30ddab5 100644
--- a/drivers/firmware/Makefile
+++ b/drivers/firmware/Makefile
@@ -14,6 +14,9 @@ obj-$(CONFIG_INTEL_STRATIX10_SERVICE) += stratix10-svc.o
obj-$(CONFIG_INTEL_STRATIX10_RSU) += stratix10-rsu.o
obj-$(CONFIG_ISCSI_IBFT_FIND) += iscsi_ibft_find.o
obj-$(CONFIG_ISCSI_IBFT) += iscsi_ibft.o
+KASAN_SANITIZE_iscsi_ibft.o := n
+KCOV_INSTRUMENT_iscsi_ibft.o := n
+
obj-$(CONFIG_FIRMWARE_MEMMAP) += memmap.o
obj-$(CONFIG_RASPBERRYPI_FIRMWARE) += raspberrypi.o
obj-$(CONFIG_FW_CFG_SYSFS) += qemu_fw_cfg.o
--
1.8.3.1

2021-01-28 00:13:36

by Dmitry Vyukov

Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
<[email protected]> wrote:
>
> On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
> > During boot of kernel with CONFIG_KASAN the following KASAN false
> > positive failure will occur when ibft_init() reads the
> > ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
> >
> > The ACPI iBFT table is not allocated, and the iscsi driver uses
> > a pointer to it to calculate checksum, etc. KASAN complains
> > about this pointer with use-after-free, which this is not.
> >
>
> Andrey, Alexander, Dmitry,
>
> I think this is the right way for this, but was wondering if you have
> other suggestions?
>
> Thanks!

Hi George, Konrad,

Please provide a sample KASAN report and kernel version to match line numbers.

Why does KASAN think the address is freed? For that to happen that
memory should have been freed. I don't remember any similar false
positives from KASAN, so this looks a bit suspicious.


> > Signed-off-by: George Kennedy <[email protected]>
> > ---
> > drivers/firmware/Makefile | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
> > index 5e013b6..30ddab5 100644
> > --- a/drivers/firmware/Makefile
> > +++ b/drivers/firmware/Makefile
> > @@ -14,6 +14,9 @@ obj-$(CONFIG_INTEL_STRATIX10_SERVICE) += stratix10-svc.o
> > obj-$(CONFIG_INTEL_STRATIX10_RSU) += stratix10-rsu.o
> > obj-$(CONFIG_ISCSI_IBFT_FIND) += iscsi_ibft_find.o
> > obj-$(CONFIG_ISCSI_IBFT) += iscsi_ibft.o
> > +KASAN_SANITIZE_iscsi_ibft.o := n
> > +KCOV_INSTRUMENT_iscsi_ibft.o := n
> > +
> > obj-$(CONFIG_FIRMWARE_MEMMAP) += memmap.o
> > obj-$(CONFIG_RASPBERRYPI_FIRMWARE) += raspberrypi.o
> > obj-$(CONFIG_FW_CFG_SYSFS) += qemu_fw_cfg.o
> > --
> > 1.8.3.1
> >

2021-01-28 00:15:05

by Konrad Rzeszutek Wilk

Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
> During boot of kernel with CONFIG_KASAN the following KASAN false
> positive failure will occur when ibft_init() reads the
> ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
>
> The ACPI iBFT table is not allocated, and the iscsi driver uses
> a pointer to it to calculate checksum, etc. KASAN complains
> about this pointer with use-after-free, which this is not.
>

Andrey, Alexander, Dmitry,

I think this is the right way for this, but was wondering if you have
other suggestions?

Thanks!
> Signed-off-by: George Kennedy <[email protected]>
> ---
> drivers/firmware/Makefile | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
> index 5e013b6..30ddab5 100644
> --- a/drivers/firmware/Makefile
> +++ b/drivers/firmware/Makefile
> @@ -14,6 +14,9 @@ obj-$(CONFIG_INTEL_STRATIX10_SERVICE) += stratix10-svc.o
> obj-$(CONFIG_INTEL_STRATIX10_RSU) += stratix10-rsu.o
> obj-$(CONFIG_ISCSI_IBFT_FIND) += iscsi_ibft_find.o
> obj-$(CONFIG_ISCSI_IBFT) += iscsi_ibft.o
> +KASAN_SANITIZE_iscsi_ibft.o := n
> +KCOV_INSTRUMENT_iscsi_ibft.o := n
> +
> obj-$(CONFIG_FIRMWARE_MEMMAP) += memmap.o
> obj-$(CONFIG_RASPBERRYPI_FIRMWARE) += raspberrypi.o
> obj-$(CONFIG_FW_CFG_SYSFS) += qemu_fw_cfg.o
> --
> 1.8.3.1
>

2021-01-28 00:27:13

by George Kennedy

Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

Hi Dmitry,

On 1/27/2021 1:48 PM, Dmitry Vyukov wrote:
> On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
> <[email protected]> wrote:
>> On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
>>> During boot of kernel with CONFIG_KASAN the following KASAN false
>>> positive failure will occur when ibft_init() reads the
>>> ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
>>>
>>> The ACPI iBFT table is not allocated, and the iscsi driver uses
>>> a pointer to it to calculate checksum, etc. KASAN complains
>>> about this pointer with use-after-free, which this is not.
>>>
>> Andrey, Alexander, Dmitry,
>>
>> I think this is the right way for this, but was wondering if you have
>> other suggestions?
>>
>> Thanks!
> Hi George, Konrad,
>
> Please provide a sample KASAN report and kernel version to match line numbers.

5.4.17-2102.200.0.0.20210106_0000

[ 24.413536] iBFT detected.
[ 24.414074]
==================================================================
[ 24.407342] BUG: KASAN: use-after-free in ibft_init+0x134/0xb8b
[ 24.407342] Read of size 4 at addr ffff8880be452004 by task swapper/0/1
[ 24.407342]
[ 24.407342] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.4.17-2102.200.0.0.20210106_0000.syzk #1
[ 24.407342] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
[ 24.407342] Call Trace:
[ 24.407342] dump_stack+0xd4/0x119
[ 24.407342] ? ibft_init+0x134/0xb8b
[ 24.407342] print_address_description.constprop.6+0x20/0x220
[ 24.407342] ? ibft_init+0x134/0xb8b
[ 24.407342] ? ibft_init+0x134/0xb8b
[ 24.407342] __kasan_report.cold.9+0x37/0x77
[ 24.407342] ? ibft_init+0x134/0xb8b
[ 24.407342] kasan_report+0x14/0x1b
[ 24.407342] __asan_report_load_n_noabort+0xf/0x11
[ 24.407342] ibft_init+0x134/0xb8b
[ 24.407342] ? dmi_sysfs_init+0x1a5/0x1a5
[ 24.407342] ? dmi_walk+0x72/0x89
[ 24.407342] ? ibft_check_initiator_for+0x159/0x159
[ 24.407342] ? rvt_init_port+0x110/0x101
[ 24.407342] ? ibft_check_initiator_for+0x159/0x159
[ 24.407342] do_one_initcall+0xc3/0x44d
[ 24.407342] ? perf_trace_initcall_level+0x410/0x405
[ 24.407342] kernel_init_freeable+0x551/0x673
[ 24.407342] ? start_kernel+0x94b/0x94b
[ 24.407342] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
[ 24.407342] ? __kasan_check_write+0x14/0x16
[ 24.407342] ? rest_init+0xe6/0xe6
[ 24.407342] kernel_init+0x16/0x1bd
[ 24.407342] ? rest_init+0xe6/0xe6
[ 24.407342] ret_from_fork+0x2b/0x36
[ 24.407342]
[ 24.407342] The buggy address belongs to the page:
[ 24.407342] page:ffffea0002f91480 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1
[ 24.407342] flags: 0xfffffc0000000()
[ 24.407342] raw: 000fffffc0000000 ffffea0002fca588 ffffea0002fb1a88 0000000000000000
[ 24.407342] raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
[ 24.407342] page dumped because: kasan: bad access detected
[ 24.407342]
[ 24.407342] Memory state around the buggy address:
[ 24.407342] ffff8880be451f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 24.407342] ffff8880be451f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 24.407342] >ffff8880be452000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 24.407342] ^
[ 24.407342] ffff8880be452080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 24.407342] ffff8880be452100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 24.407342]
==================================================================
[ 24.407342] Disabling lock debugging due to kernel taint
[ 24.451021] Kernel panic - not syncing: panic_on_warn set ...
[ 24.452002] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G B 5.4.17-2102.200.0.0.20210106_0000.syzk #1
[ 24.452002] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
[ 24.452002] Call Trace:
[ 24.452002] dump_stack+0xd4/0x119
[ 24.452002] ? ibft_init+0x102/0xb8b
[ 24.452002] panic+0x28f/0x6e0
[ 24.452002] ? __warn_printk+0xe0/0xe0
[ 24.452002] ? ibft_init+0x134/0xb8b
[ 24.452002] ? add_taint+0x68/0xb3
[ 24.452002] ? add_taint+0x68/0xb3
[ 24.452002] ? ibft_init+0x134/0xb8b
[ 24.452002] ? ibft_init+0x134/0xb8b
[ 24.452002] end_report+0x4c/0x54
[ 24.452002] __kasan_report.cold.9+0x55/0x77
[ 24.452002] ? ibft_init+0x134/0xb8b
[ 24.452002] kasan_report+0x14/0x1b
[ 24.452002] __asan_report_load_n_noabort+0xf/0x11
[ 24.452002] ibft_init+0x134/0xb8b
[ 24.452002] ? dmi_sysfs_init+0x1a5/0x1a5
[ 24.452002] ? dmi_walk+0x72/0x89
[ 24.452002] ? ibft_check_initiator_for+0x159/0x159
[ 24.452002] ? rvt_init_port+0x110/0x101
[ 24.452002] ? ibft_check_initiator_for+0x159/0x159
[ 24.452002] do_one_initcall+0xc3/0x44d
[ 24.452002] ? perf_trace_initcall_level+0x410/0x405
[ 24.452002] kernel_init_freeable+0x551/0x673
[ 24.452002] ? start_kernel+0x94b/0x94b
[ 24.452002] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
[ 24.452002] ? __kasan_check_write+0x14/0x16
[ 24.452002] ? rest_init+0xe6/0xe6
[ 24.452002] kernel_init+0x16/0x1bd
[ 24.452002] ? rest_init+0xe6/0xe6
[ 24.452002] ret_from_fork+0x2b/0x36
[ 24.452002] Dumping ftrace buffer:
[ 24.452002] ---------------------------------
[ 24.452002] swapper/-1 1.... 24564337us : rdmaip_init: 2924: rdmaip_init: Active Bonding is DISABLED
[ 24.452002] ---------------------------------
[ 24.452002] Kernel Offset: disabled
[ 24.452002] Rebooting in 1 seconds..

> Why does KASAN think the address is freed? For that to happen that
> memory should have been freed. I don't remember any similar false
> positives from KASAN, so this looks a bit suspicious.

I'm not sure why KASAN thinks the address is freed. There are other modules where KASAN/KCOV is disabled on boot.
Could this be for a similar reason?

Thank you,
George

>>> Signed-off-by: George Kennedy <[email protected]>
>>> ---
>>> drivers/firmware/Makefile | 3 +++
>>> 1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
>>> index 5e013b6..30ddab5 100644
>>> --- a/drivers/firmware/Makefile
>>> +++ b/drivers/firmware/Makefile
>>> @@ -14,6 +14,9 @@ obj-$(CONFIG_INTEL_STRATIX10_SERVICE) += stratix10-svc.o
>>> obj-$(CONFIG_INTEL_STRATIX10_RSU) += stratix10-rsu.o
>>> obj-$(CONFIG_ISCSI_IBFT_FIND) += iscsi_ibft_find.o
>>> obj-$(CONFIG_ISCSI_IBFT) += iscsi_ibft.o
>>> +KASAN_SANITIZE_iscsi_ibft.o := n
>>> +KCOV_INSTRUMENT_iscsi_ibft.o := n
>>> +
>>> obj-$(CONFIG_FIRMWARE_MEMMAP) += memmap.o
>>> obj-$(CONFIG_RASPBERRYPI_FIRMWARE) += raspberrypi.o
>>> obj-$(CONFIG_FW_CFG_SYSFS) += qemu_fw_cfg.o
>>> --
>>> 1.8.3.1
>>>

2021-01-28 00:32:02

by Dmitry Vyukov

Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

On Wed, Jan 27, 2021 at 9:01 PM George Kennedy
<[email protected]> wrote:
>
> Hi Dmitry,
>
> On 1/27/2021 1:48 PM, Dmitry Vyukov wrote:
>
> On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
> <[email protected]> wrote:
>
> On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
>
> During boot of kernel with CONFIG_KASAN the following KASAN false
> positive failure will occur when ibft_init() reads the
> ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
>
> The ACPI iBFT table is not allocated, and the iscsi driver uses
> a pointer to it to calculate checksum, etc. KASAN complains
> about this pointer with use-after-free, which this is not.
>
> Andrey, Alexander, Dmitry,
>
> I think this is the right way for this, but was wondering if you have
> other suggestions?
>
> Thanks!
>
> Hi George, Konrad,
>
> Please provide a sample KASAN report and kernel version to match line numbers.
>
> 5.4.17-2102.200.0.0.20210106_0000
>
> [ 24.413536] iBFT detected.
> [ 24.414074]
> ==================================================================
> [ 24.407342] BUG: KASAN: use-after-free in ibft_init+0x134/0xb8b
> [ 24.407342] Read of size 4 at addr ffff8880be452004 by task swapper/0/1
> [ 24.407342]
> [ 24.407342] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.4.17-2102.200.0.0.20210106_0000.syzk #1
> [ 24.407342] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> [ 24.407342] Call Trace:
> [ 24.407342] dump_stack+0xd4/0x119
> [ 24.407342] ? ibft_init+0x134/0xb8b
> [ 24.407342] print_address_description.constprop.6+0x20/0x220
> [ 24.407342] ? ibft_init+0x134/0xb8b
> [ 24.407342] ? ibft_init+0x134/0xb8b
> [ 24.407342] __kasan_report.cold.9+0x37/0x77
> [ 24.407342] ? ibft_init+0x134/0xb8b
> [ 24.407342] kasan_report+0x14/0x1b
> [ 24.407342] __asan_report_load_n_noabort+0xf/0x11
> [ 24.407342] ibft_init+0x134/0xb8b
> [ 24.407342] ? dmi_sysfs_init+0x1a5/0x1a5
> [ 24.407342] ? dmi_walk+0x72/0x89
> [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
> [ 24.407342] ? rvt_init_port+0x110/0x101
> [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
> [ 24.407342] do_one_initcall+0xc3/0x44d
> [ 24.407342] ? perf_trace_initcall_level+0x410/0x405
> [ 24.407342] kernel_init_freeable+0x551/0x673
> [ 24.407342] ? start_kernel+0x94b/0x94b
> [ 24.407342] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
> [ 24.407342] ? __kasan_check_write+0x14/0x16
> [ 24.407342] ? rest_init+0xe6/0xe6
> [ 24.407342] kernel_init+0x16/0x1bd
> [ 24.407342] ? rest_init+0xe6/0xe6
> [ 24.407342] ret_from_fork+0x2b/0x36
> [ 24.407342]
> [ 24.407342] The buggy address belongs to the page:
> [ 24.407342] page:ffffea0002f91480 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1
> [ 24.407342] flags: 0xfffffc0000000()
> [ 24.407342] raw: 000fffffc0000000 ffffea0002fca588 ffffea0002fb1a88 0000000000000000
> [ 24.407342] raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
> [ 24.407342] page dumped because: kasan: bad access detected
> [ 24.407342]
> [ 24.407342] Memory state around the buggy address:
> [ 24.407342] ffff8880be451f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> [ 24.407342] ffff8880be451f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> [ 24.407342] >ffff8880be452000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> [ 24.407342] ^
> [ 24.407342] ffff8880be452080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> [ 24.407342] ffff8880be452100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> [ 24.407342]
> ==================================================================
> [ 24.407342] Disabling lock debugging due to kernel taint
> [ 24.451021] Kernel panic - not syncing: panic_on_warn set ...
> [ 24.452002] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G B 5.4.17-2102.200.0.0.20210106_0000.syzk #1
> [ 24.452002] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> [ 24.452002] Call Trace:
> [ 24.452002] dump_stack+0xd4/0x119
> [ 24.452002] ? ibft_init+0x102/0xb8b
> [ 24.452002] panic+0x28f/0x6e0
> [ 24.452002] ? __warn_printk+0xe0/0xe0
> [ 24.452002] ? ibft_init+0x134/0xb8b
> [ 24.452002] ? add_taint+0x68/0xb3
> [ 24.452002] ? add_taint+0x68/0xb3
> [ 24.452002] ? ibft_init+0x134/0xb8b
> [ 24.452002] ? ibft_init+0x134/0xb8b
> [ 24.452002] end_report+0x4c/0x54
> [ 24.452002] __kasan_report.cold.9+0x55/0x77
> [ 24.452002] ? ibft_init+0x134/0xb8b
> [ 24.452002] kasan_report+0x14/0x1b
> [ 24.452002] __asan_report_load_n_noabort+0xf/0x11
> [ 24.452002] ibft_init+0x134/0xb8b
> [ 24.452002] ? dmi_sysfs_init+0x1a5/0x1a5
> [ 24.452002] ? dmi_walk+0x72/0x89
> [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
> [ 24.452002] ? rvt_init_port+0x110/0x101
> [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
> [ 24.452002] do_one_initcall+0xc3/0x44d
> [ 24.452002] ? perf_trace_initcall_level+0x410/0x405
> [ 24.452002] kernel_init_freeable+0x551/0x673
> [ 24.452002] ? start_kernel+0x94b/0x94b
> [ 24.452002] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
> [ 24.452002] ? __kasan_check_write+0x14/0x16
> [ 24.452002] ? rest_init+0xe6/0xe6
> [ 24.452002] kernel_init+0x16/0x1bd
> [ 24.452002] ? rest_init+0xe6/0xe6
> [ 24.452002] ret_from_fork+0x2b/0x36
> [ 24.452002] Dumping ftrace buffer:
> [ 24.452002] ---------------------------------
> [ 24.452002] swapper/-1 1.... 24564337us : rdmaip_init: 2924: rdmaip_init: Active Bonding is DISABLED
> [ 24.452002] ---------------------------------
> [ 24.452002] Kernel Offset: disabled
> [ 24.452002] Rebooting in 1 seconds..
>
> Why does KASAN think the address is freed? For that to happen that
> memory should have been freed. I don't remember any similar false
> positives from KASAN, so this looks a bit suspicious.
>
> I'm not sure why KASAN thinks the address is freed. There are other modules where KASAN/KCOV is disabled on boot.
> Could this be for a similar reason?

Most of these files are disabled because they cause recursion in
instrumentation, or execute too early in bootstrap process (before
kasan_init).

Somehow the table pointer in ibft_init points to a freed page. I
tracked it down to here:
https://elixir.bootlin.com/linux/v5.4.17/source/drivers/acpi/acpica/tbutils.c#L399
but I can't find where this table_desc->pointer comes from. Perhaps it
uses some allocation method that's not supported by KASAN? However,
it's the only such case that I've seen, so it's a bit weird. Could it
use something like memblock_alloc? Or maybe that page was in fact
freed?... Too bad KASAN does not print free stack for pages, maybe
it's not too hard to do if CONFIG_PAGE_OWNER is enabled...



> Thank you,
> George
>
>
> Signed-off-by: George Kennedy <[email protected]>
> ---
> drivers/firmware/Makefile | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
> index 5e013b6..30ddab5 100644
> --- a/drivers/firmware/Makefile
> +++ b/drivers/firmware/Makefile
> @@ -14,6 +14,9 @@ obj-$(CONFIG_INTEL_STRATIX10_SERVICE) += stratix10-svc.o
> obj-$(CONFIG_INTEL_STRATIX10_RSU) += stratix10-rsu.o
> obj-$(CONFIG_ISCSI_IBFT_FIND) += iscsi_ibft_find.o
> obj-$(CONFIG_ISCSI_IBFT) += iscsi_ibft.o
> +KASAN_SANITIZE_iscsi_ibft.o := n
> +KCOV_INSTRUMENT_iscsi_ibft.o := n
> +
> obj-$(CONFIG_FIRMWARE_MEMMAP) += memmap.o
> obj-$(CONFIG_RASPBERRYPI_FIRMWARE) += raspberrypi.o
> obj-$(CONFIG_FW_CFG_SYSFS) += qemu_fw_cfg.o
> --
> 1.8.3.1
>
>

2021-02-03 19:32:31

by Konrad Rzeszutek Wilk

Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

Hey Dmitry, Rafael, George, please see below..

On Wed, Jan 27, 2021 at 10:10:07PM +0100, Dmitry Vyukov wrote:
> On Wed, Jan 27, 2021 at 9:01 PM George Kennedy
> <[email protected]> wrote:
> >
> > Hi Dmitry,
> >
> > On 1/27/2021 1:48 PM, Dmitry Vyukov wrote:
> >
> > On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
> > <[email protected]> wrote:
> >
> > On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
> >
> > During boot of kernel with CONFIG_KASAN the following KASAN false
> > positive failure will occur when ibft_init() reads the
> > ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
> >
> > The ACPI iBFT table is not allocated, and the iscsi driver uses
> > a pointer to it to calculate checksum, etc. KASAN complains
> > about this pointer with use-after-free, which this is not.
> >
> > Andrey, Alexander, Dmitry,
> >
> > I think this is the right way for this, but was wondering if you have
> > other suggestions?
> >
> > Thanks!
> >
> > Hi George, Konrad,
> >
> > Please provide a sample KASAN report and kernel version to match line numbers.
> >
> > 5.4.17-2102.200.0.0.20210106_0000
> >
> > [ 24.413536] iBFT detected.
> > [ 24.414074]
> > ==================================================================
> > [ 24.407342] BUG: KASAN: use-after-free in ibft_init+0x134/0xb8b
> > [ 24.407342] Read of size 4 at addr ffff8880be452004 by task swapper/0/1
> > [ 24.407342]
> > [ 24.407342] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.4.17-2102.200.0.0.20210106_0000.syzk #1
> > [ 24.407342] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> > [ 24.407342] Call Trace:
> > [ 24.407342] dump_stack+0xd4/0x119
> > [ 24.407342] ? ibft_init+0x134/0xb8b
> > [ 24.407342] print_address_description.constprop.6+0x20/0x220
> > [ 24.407342] ? ibft_init+0x134/0xb8b
> > [ 24.407342] ? ibft_init+0x134/0xb8b
> > [ 24.407342] __kasan_report.cold.9+0x37/0x77
> > [ 24.407342] ? ibft_init+0x134/0xb8b
> > [ 24.407342] kasan_report+0x14/0x1b
> > [ 24.407342] __asan_report_load_n_noabort+0xf/0x11
> > [ 24.407342] ibft_init+0x134/0xb8b
> > [ 24.407342] ? dmi_sysfs_init+0x1a5/0x1a5
> > [ 24.407342] ? dmi_walk+0x72/0x89
> > [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
> > [ 24.407342] ? rvt_init_port+0x110/0x101
> > [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
> > [ 24.407342] do_one_initcall+0xc3/0x44d
> > [ 24.407342] ? perf_trace_initcall_level+0x410/0x405
> > [ 24.407342] kernel_init_freeable+0x551/0x673
> > [ 24.407342] ? start_kernel+0x94b/0x94b
> > [ 24.407342] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
> > [ 24.407342] ? __kasan_check_write+0x14/0x16
> > [ 24.407342] ? rest_init+0xe6/0xe6
> > [ 24.407342] kernel_init+0x16/0x1bd
> > [ 24.407342] ? rest_init+0xe6/0xe6
> > [ 24.407342] ret_from_fork+0x2b/0x36
> > [ 24.407342]
> > [ 24.407342] The buggy address belongs to the page:
> > [ 24.407342] page:ffffea0002f91480 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1
> > [ 24.407342] flags: 0xfffffc0000000()
> > [ 24.407342] raw: 000fffffc0000000 ffffea0002fca588 ffffea0002fb1a88 0000000000000000
> > [ 24.407342] raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
> > [ 24.407342] page dumped because: kasan: bad access detected
> > [ 24.407342]
> > [ 24.407342] Memory state around the buggy address:
> > [ 24.407342] ffff8880be451f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > [ 24.407342] ffff8880be451f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > [ 24.407342] >ffff8880be452000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > [ 24.407342] ^
> > [ 24.407342] ffff8880be452080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > [ 24.407342] ffff8880be452100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > [ 24.407342]
> > ==================================================================
> > [ 24.407342] Disabling lock debugging due to kernel taint
> > [ 24.451021] Kernel panic - not syncing: panic_on_warn set ...
> > [ 24.452002] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G B 5.4.17-2102.200.0.0.20210106_0000.syzk #1
> > [ 24.452002] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> > [ 24.452002] Call Trace:
> > [ 24.452002] dump_stack+0xd4/0x119
> > [ 24.452002] ? ibft_init+0x102/0xb8b
> > [ 24.452002] panic+0x28f/0x6e0
> > [ 24.452002] ? __warn_printk+0xe0/0xe0
> > [ 24.452002] ? ibft_init+0x134/0xb8b
> > [ 24.452002] ? add_taint+0x68/0xb3
> > [ 24.452002] ? add_taint+0x68/0xb3
> > [ 24.452002] ? ibft_init+0x134/0xb8b
> > [ 24.452002] ? ibft_init+0x134/0xb8b
> > [ 24.452002] end_report+0x4c/0x54
> > [ 24.452002] __kasan_report.cold.9+0x55/0x77
> > [ 24.452002] ? ibft_init+0x134/0xb8b
> > [ 24.452002] kasan_report+0x14/0x1b
> > [ 24.452002] __asan_report_load_n_noabort+0xf/0x11
> > [ 24.452002] ibft_init+0x134/0xb8b
> > [ 24.452002] ? dmi_sysfs_init+0x1a5/0x1a5
> > [ 24.452002] ? dmi_walk+0x72/0x89
> > [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
> > [ 24.452002] ? rvt_init_port+0x110/0x101
> > [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
> > [ 24.452002] do_one_initcall+0xc3/0x44d
> > [ 24.452002] ? perf_trace_initcall_level+0x410/0x405
> > [ 24.452002] kernel_init_freeable+0x551/0x673
> > [ 24.452002] ? start_kernel+0x94b/0x94b
> > [ 24.452002] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
> > [ 24.452002] ? __kasan_check_write+0x14/0x16
> > [ 24.452002] ? rest_init+0xe6/0xe6
> > [ 24.452002] kernel_init+0x16/0x1bd
> > [ 24.452002] ? rest_init+0xe6/0xe6
> > [ 24.452002] ret_from_fork+0x2b/0x36
> > [ 24.452002] Dumping ftrace buffer:
> > [ 24.452002] ---------------------------------
> > [ 24.452002] swapper/-1 1.... 24564337us : rdmaip_init: 2924: rdmaip_init: Active Bonding is DISABLED
> > [ 24.452002] ---------------------------------
> > [ 24.452002] Kernel Offset: disabled
> > [ 24.452002] Rebooting in 1 seconds..
> >
> > Why does KASAN think the address is freed? For that to happen that
> > memory should have been freed. I don't remember any similar false
> > positives from KASAN, so this looks a bit suspicious.
> >
> > I'm not sure why KASAN thinks the address is freed. There are other modules where KASAN/KCOV is disabled on boot.
> > Could this be for a similar reason?
>
> Most of these files are disabled because they cause recursion in
> instrumentation, or execute too early in bootstrap process (before
> kasan_init).
>
> Somehow the table pointer in ibft_init points to a freed page. I
> tracked it down to here:
> https://elixir.bootlin.com/linux/v5.4.17/source/drivers/acpi/acpica/tbutils.c#L399
> but I can't find where this table_desc->pointer comes from. Perhaps it

It is what the BIOS generated. It usually points to some memory
location in right under 4GB and the BIOS stashes the DSDT, iBFT, and
other tables in there.

> uses some allocation method that's not supported by KASAN? However,
> it's the only such case that I've seen, so it's a bit weird. Could it
> use something like memblock_alloc? Or maybe that page was in fact
> freed?... Too bad KASAN does not print free stack for pages, maybe
> it's not too hard to do if CONFIG_PAGE_OWNER is enabled...

Hm, there is a comment in the acpi_get_table speaking about the
requirement of having a acpi_put_table and:


* DESCRIPTION: Finds and verifies an ACPI table. Table must be in the
* RSDT/XSDT.
* Note that an early stage acpi_get_table() call must be paired
* with an early stage acpi_put_table() call. otherwise the table
* pointer mapped by the early stage mapping implementation may be
* erroneously unmapped by the late stage unmapping implementation
* in an acpi_put_table() invoked during the late stage.
*

Which would imply that I should use acpi_put_table in the error path
(see below a patch), but also copy the structure instead of depending
on ACPI keeping it mapped for me. I think.

CC-ing Rafeal.


From c37da50fdfc62cd4f7b23562b55661478c90a17d Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <[email protected]>
Date: Tue, 2 Feb 2021 17:28:28 +0000
Subject: [PATCH] ibft: Put ibft_addr back

Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
---
drivers/firmware/iscsi_ibft.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/drivers/firmware/iscsi_ibft.c b/drivers/firmware/iscsi_ibft.c
index 7127a04..2a1a033 100644
--- a/drivers/firmware/iscsi_ibft.c
+++ b/drivers/firmware/iscsi_ibft.c
@@ -811,6 +811,10 @@ static void ibft_cleanup(void)
ibft_unregister();
iscsi_boot_destroy_kset(boot_kset);
}
+ if (ibft_addr) {
+ acpi_put_table((struct acpi_table_header *)ibft_addr);
+ ibft_addr = NULL;
+ }
}

static void __exit ibft_exit(void)
@@ -835,13 +839,15 @@ static void __init acpi_find_ibft_region(void)
{
int i;
struct acpi_table_header *table = NULL;
+ acpi_status status;

if (acpi_disabled)
return;

for (i = 0; i < ARRAY_SIZE(ibft_signs) && !ibft_addr; i++) {
- acpi_get_table(ibft_signs[i].sign, 0, &table);
- ibft_addr = (struct acpi_table_ibft *)table;
+ status = acpi_get_table(ibft_signs[i].sign, 0, &table);
+ if (ACPI_SUCCESS(status))
+ ibft_addr = (struct acpi_table_ibft *)table;
}
}
#else
@@ -870,12 +876,13 @@ static int __init ibft_init(void)

rc = ibft_check_device();
if (rc)
- return rc;
+ goto out_free;

boot_kset = iscsi_boot_create_kset("ibft");
- if (!boot_kset)
- return -ENOMEM;
-
+ if (!boot_kset) {
+ rc = -ENOMEM;
+ goto out_free;
+ }
/* Scan the IBFT for data and register the kobjects. */
rc = ibft_register_kobjects(ibft_addr);
if (rc)
--
1.8.3.1

2021-02-03 19:40:57

by Dmitry Vyukov

Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

On Wed, Feb 3, 2021 at 8:29 PM Konrad Rzeszutek Wilk <[email protected]> wrote:
>
> Hey Dmitry, Rafael, George, please see below..
>
> On Wed, Jan 27, 2021 at 10:10:07PM +0100, Dmitry Vyukov wrote:
> > On Wed, Jan 27, 2021 at 9:01 PM George Kennedy
> > <[email protected]> wrote:
> > >
> > > Hi Dmitry,
> > >
> > > On 1/27/2021 1:48 PM, Dmitry Vyukov wrote:
> > >
> > > On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
> > > <[email protected]> wrote:
> > >
> > > On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
> > >
> > > During boot of kernel with CONFIG_KASAN the following KASAN false
> > > positive failure will occur when ibft_init() reads the
> > > ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
> > >
> > > The ACPI iBFT table is not allocated, and the iscsi driver uses
> > > a pointer to it to calculate checksum, etc. KASAN complains
> > > about this pointer with use-after-free, which this is not.
> > >
> > > Andrey, Alexander, Dmitry,
> > >
> > > I think this is the right way for this, but was wondering if you have
> > > other suggestions?
> > >
> > > Thanks!
> > >
> > > Hi George, Konrad,
> > >
> > > Please provide a sample KASAN report and kernel version to match line numbers.
> > >
> > > 5.4.17-2102.200.0.0.20210106_0000
> > >
> > > [ 24.413536] iBFT detected.
> > > [ 24.414074]
> > > ==================================================================
> > > [ 24.407342] BUG: KASAN: use-after-free in ibft_init+0x134/0xb8b
> > > [ 24.407342] Read of size 4 at addr ffff8880be452004 by task swapper/0/1
> > > [ 24.407342]
> > > [ 24.407342] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.4.17-2102.200.0.0.20210106_0000.syzk #1
> > > [ 24.407342] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> > > [ 24.407342] Call Trace:
> > > [ 24.407342] dump_stack+0xd4/0x119
> > > [ 24.407342] ? ibft_init+0x134/0xb8b
> > > [ 24.407342] print_address_description.constprop.6+0x20/0x220
> > > [ 24.407342] ? ibft_init+0x134/0xb8b
> > > [ 24.407342] ? ibft_init+0x134/0xb8b
> > > [ 24.407342] __kasan_report.cold.9+0x37/0x77
> > > [ 24.407342] ? ibft_init+0x134/0xb8b
> > > [ 24.407342] kasan_report+0x14/0x1b
> > > [ 24.407342] __asan_report_load_n_noabort+0xf/0x11
> > > [ 24.407342] ibft_init+0x134/0xb8b
> > > [ 24.407342] ? dmi_sysfs_init+0x1a5/0x1a5
> > > [ 24.407342] ? dmi_walk+0x72/0x89
> > > [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
> > > [ 24.407342] ? rvt_init_port+0x110/0x101
> > > [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
> > > [ 24.407342] do_one_initcall+0xc3/0x44d
> > > [ 24.407342] ? perf_trace_initcall_level+0x410/0x405
> > > [ 24.407342] kernel_init_freeable+0x551/0x673
> > > [ 24.407342] ? start_kernel+0x94b/0x94b
> > > [ 24.407342] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
> > > [ 24.407342] ? __kasan_check_write+0x14/0x16
> > > [ 24.407342] ? rest_init+0xe6/0xe6
> > > [ 24.407342] kernel_init+0x16/0x1bd
> > > [ 24.407342] ? rest_init+0xe6/0xe6
> > > [ 24.407342] ret_from_fork+0x2b/0x36
> > > [ 24.407342]
> > > [ 24.407342] The buggy address belongs to the page:
> > > [ 24.407342] page:ffffea0002f91480 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1
> > > [ 24.407342] flags: 0xfffffc0000000()
> > > [ 24.407342] raw: 000fffffc0000000 ffffea0002fca588 ffffea0002fb1a88 0000000000000000
> > > [ 24.407342] raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
> > > [ 24.407342] page dumped because: kasan: bad access detected
> > > [ 24.407342]
> > > [ 24.407342] Memory state around the buggy address:
> > > [ 24.407342] ffff8880be451f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > > [ 24.407342] ffff8880be451f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > > [ 24.407342] >ffff8880be452000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > > [ 24.407342] ^
> > > [ 24.407342] ffff8880be452080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > > [ 24.407342] ffff8880be452100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > > [ 24.407342]
> > > ==================================================================
> > > [ 24.407342] Disabling lock debugging due to kernel taint
> > > [ 24.451021] Kernel panic - not syncing: panic_on_warn set ...
> > > [ 24.452002] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G B 5.4.17-2102.200.0.0.20210106_0000.syzk #1
> > > [ 24.452002] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> > > [ 24.452002] Call Trace:
> > > [ 24.452002] dump_stack+0xd4/0x119
> > > [ 24.452002] ? ibft_init+0x102/0xb8b
> > > [ 24.452002] panic+0x28f/0x6e0
> > > [ 24.452002] ? __warn_printk+0xe0/0xe0
> > > [ 24.452002] ? ibft_init+0x134/0xb8b
> > > [ 24.452002] ? add_taint+0x68/0xb3
> > > [ 24.452002] ? add_taint+0x68/0xb3
> > > [ 24.452002] ? ibft_init+0x134/0xb8b
> > > [ 24.452002] ? ibft_init+0x134/0xb8b
> > > [ 24.452002] end_report+0x4c/0x54
> > > [ 24.452002] __kasan_report.cold.9+0x55/0x77
> > > [ 24.452002] ? ibft_init+0x134/0xb8b
> > > [ 24.452002] kasan_report+0x14/0x1b
> > > [ 24.452002] __asan_report_load_n_noabort+0xf/0x11
> > > [ 24.452002] ibft_init+0x134/0xb8b
> > > [ 24.452002] ? dmi_sysfs_init+0x1a5/0x1a5
> > > [ 24.452002] ? dmi_walk+0x72/0x89
> > > [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
> > > [ 24.452002] ? rvt_init_port+0x110/0x101
> > > [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
> > > [ 24.452002] do_one_initcall+0xc3/0x44d
> > > [ 24.452002] ? perf_trace_initcall_level+0x410/0x405
> > > [ 24.452002] kernel_init_freeable+0x551/0x673
> > > [ 24.452002] ? start_kernel+0x94b/0x94b
> > > [ 24.452002] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
> > > [ 24.452002] ? __kasan_check_write+0x14/0x16
> > > [ 24.452002] ? rest_init+0xe6/0xe6
> > > [ 24.452002] kernel_init+0x16/0x1bd
> > > [ 24.452002] ? rest_init+0xe6/0xe6
> > > [ 24.452002] ret_from_fork+0x2b/0x36
> > > [ 24.452002] Dumping ftrace buffer:
> > > [ 24.452002] ---------------------------------
> > > [ 24.452002] swapper/-1 1.... 24564337us : rdmaip_init: 2924: rdmaip_init: Active Bonding is DISABLED
> > > [ 24.452002] ---------------------------------
> > > [ 24.452002] Kernel Offset: disabled
> > > [ 24.452002] Rebooting in 1 seconds..
> > >
> > > Why does KASAN think the address is freed? For that to happen that
> > > memory should have been freed. I don't remember any similar false
> > > positives from KASAN, so this looks a bit suspicious.
> > >
> > > I'm not sure why KASAN thinks the address is freed. There are other modules where KASAN/KCOV is disabled on boot.
> > > Could this be for a similar reason?
> >
> > Most of these files are disabled because they cause recursion in
> > instrumentation, or execute too early in bootstrap process (before
> > kasan_init).
> >
> > Somehow the table pointer in ibft_init points to a freed page. I
> > tracked it down to here:
> > https://elixir.bootlin.com/linux/v5.4.17/source/drivers/acpi/acpica/tbutils.c#L399
> > but I can't find where this table_desc->pointer comes from. Perhaps it
>
> It is what the BIOS generated. It usually points to some memory
> location in right under 4GB and the BIOS stashes the DSDT, iBFT, and
> other tables in there.
>
> > uses some allocation method that's not supported by KASAN? However,
> > it's the only such case that I've seen, so it's a bit weird. Could it
> > use something like memblock_alloc? Or maybe that page was in fact
> > freed?... Too bad KASAN does not print free stack for pages, maybe
> > it's not too hard to do if CONFIG_PAGE_OWNER is enabled...
>
> Hm, there is a comment in the acpi_get_table speaking about the
> requirement of having a acpi_put_table and:
>
>
> * DESCRIPTION: Finds and verifies an ACPI table. Table must be in the
> * RSDT/XSDT.
> * Note that an early stage acpi_get_table() call must be paired
> * with an early stage acpi_put_table() call. otherwise the table
> * pointer mapped by the early stage mapping implementation may be
> * erroneously unmapped by the late stage unmapping implementation
> * in an acpi_put_table() invoked during the late stage.
> *
>
> Which would imply that I should use acpi_put_table in the error path
> (see below a patch), but also copy the structure instead of depending
> on ACPI keeping it mapped for me. I think.

Hi Konrad,

Thanks for looking into this.
If ACPI unmaps this page, that would perfectly explain the KASAN report.

George, does this patch eliminate the KASAN report for you?


> CC-ing Rafeal.
>
>
> From c37da50fdfc62cd4f7b23562b55661478c90a17d Mon Sep 17 00:00:00 2001
> From: Konrad Rzeszutek Wilk <[email protected]>
> Date: Tue, 2 Feb 2021 17:28:28 +0000
> Subject: [PATCH] ibft: Put ibft_addr back
>
> Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
> ---
> drivers/firmware/iscsi_ibft.c | 19 +++++++++++++------
> 1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/firmware/iscsi_ibft.c b/drivers/firmware/iscsi_ibft.c
> index 7127a04..2a1a033 100644
> --- a/drivers/firmware/iscsi_ibft.c
> +++ b/drivers/firmware/iscsi_ibft.c
> @@ -811,6 +811,10 @@ static void ibft_cleanup(void)
> ibft_unregister();
> iscsi_boot_destroy_kset(boot_kset);
> }
> + if (ibft_addr) {
> + acpi_put_table((struct acpi_table_header *)ibft_addr);
> + ibft_addr = NULL;
> + }
> }
>
> static void __exit ibft_exit(void)
> @@ -835,13 +839,15 @@ static void __init acpi_find_ibft_region(void)
> {
> int i;
> struct acpi_table_header *table = NULL;
> + acpi_status status;
>
> if (acpi_disabled)
> return;
>
> for (i = 0; i < ARRAY_SIZE(ibft_signs) && !ibft_addr; i++) {
> - acpi_get_table(ibft_signs[i].sign, 0, &table);
> - ibft_addr = (struct acpi_table_ibft *)table;
> + status = acpi_get_table(ibft_signs[i].sign, 0, &table);
> + if (ACPI_SUCCESS(status))
> + ibft_addr = (struct acpi_table_ibft *)table;
> }
> }
> #else
> @@ -870,12 +876,13 @@ static int __init ibft_init(void)
>
> rc = ibft_check_device();
> if (rc)
> - return rc;
> + goto out_free;
>
> boot_kset = iscsi_boot_create_kset("ibft");
> - if (!boot_kset)
> - return -ENOMEM;
> -
> + if (!boot_kset) {
> + rc = -ENOMEM;
> + goto out_free;
> + }
> /* Scan the IBFT for data and register the kobjects. */
> rc = ibft_register_kobjects(ibft_addr);
> if (rc)
> --
> 1.8.3.1
>

2021-02-10 21:53:59

by George Kennedy

Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

On 2/3/2021 2:35 PM, Dmitry Vyukov wrote:
> On Wed, Feb 3, 2021 at 8:29 PM Konrad Rzeszutek Wilk <[email protected]> wrote:
>> Hey Dmitry, Rafael, George, please see below..
>>
>> On Wed, Jan 27, 2021 at 10:10:07PM +0100, Dmitry Vyukov wrote:
>>> On Wed, Jan 27, 2021 at 9:01 PM George Kennedy
>>> <[email protected]> wrote:
>>>> Hi Dmitry,
>>>>
>>>> On 1/27/2021 1:48 PM, Dmitry Vyukov wrote:
>>>>
>>>> On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
>>>> <[email protected]> wrote:
>>>>
>>>> On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
>>>>
>>>> During boot of kernel with CONFIG_KASAN the following KASAN false
>>>> positive failure will occur when ibft_init() reads the
>>>> ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
>>>>
>>>> The ACPI iBFT table is not allocated, and the iscsi driver uses
>>>> a pointer to it to calculate checksum, etc. KASAN complains
>>>> about this pointer with use-after-free, which this is not.
>>>>
>>>> Andrey, Alexander, Dmitry,
>>>>
>>>> I think this is the right way for this, but was wondering if you have
>>>> other suggestions?
>>>>
>>>> Thanks!
>>>>
>>>> Hi George, Konrad,
>>>>
>>>> Please provide a sample KASAN report and kernel version to match line numbers.
>>>>
>>>> 5.4.17-2102.200.0.0.20210106_0000
>>>>
>>>> [ 24.413536] iBFT detected.
>>>> [ 24.414074]
>>>> ==================================================================
>>>> [ 24.407342] BUG: KASAN: use-after-free in ibft_init+0x134/0xb8b
>>>> [ 24.407342] Read of size 4 at addr ffff8880be452004 by task swapper/0/1
>>>> [ 24.407342]
>>>> [ 24.407342] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.4.17-2102.200.0.0.20210106_0000.syzk #1
>>>> [ 24.407342] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
>>>> [ 24.407342] Call Trace:
>>>> [ 24.407342] dump_stack+0xd4/0x119
>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>> [ 24.407342] print_address_description.constprop.6+0x20/0x220
>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>> [ 24.407342] __kasan_report.cold.9+0x37/0x77
>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>> [ 24.407342] kasan_report+0x14/0x1b
>>>> [ 24.407342] __asan_report_load_n_noabort+0xf/0x11
>>>> [ 24.407342] ibft_init+0x134/0xb8b
>>>> [ 24.407342] ? dmi_sysfs_init+0x1a5/0x1a5
>>>> [ 24.407342] ? dmi_walk+0x72/0x89
>>>> [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
>>>> [ 24.407342] ? rvt_init_port+0x110/0x101
>>>> [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
>>>> [ 24.407342] do_one_initcall+0xc3/0x44d
>>>> [ 24.407342] ? perf_trace_initcall_level+0x410/0x405
>>>> [ 24.407342] kernel_init_freeable+0x551/0x673
>>>> [ 24.407342] ? start_kernel+0x94b/0x94b
>>>> [ 24.407342] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
>>>> [ 24.407342] ? __kasan_check_write+0x14/0x16
>>>> [ 24.407342] ? rest_init+0xe6/0xe6
>>>> [ 24.407342] kernel_init+0x16/0x1bd
>>>> [ 24.407342] ? rest_init+0xe6/0xe6
>>>> [ 24.407342] ret_from_fork+0x2b/0x36
>>>> [ 24.407342]
>>>> [ 24.407342] The buggy address belongs to the page:
>>>> [ 24.407342] page:ffffea0002f91480 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1
>>>> [ 24.407342] flags: 0xfffffc0000000()
>>>> [ 24.407342] raw: 000fffffc0000000 ffffea0002fca588 ffffea0002fb1a88 0000000000000000
>>>> [ 24.407342] raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
>>>> [ 24.407342] page dumped because: kasan: bad access detected
>>>> [ 24.407342]
>>>> [ 24.407342] Memory state around the buggy address:
>>>> [ 24.407342] ffff8880be451f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> [ 24.407342] ffff8880be451f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> [ 24.407342] >ffff8880be452000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> [ 24.407342] ^
>>>> [ 24.407342] ffff8880be452080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> [ 24.407342] ffff8880be452100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> [ 24.407342]
>>>> ==================================================================
>>>> [ 24.407342] Disabling lock debugging due to kernel taint
>>>> [ 24.451021] Kernel panic - not syncing: panic_on_warn set ...
>>>> [ 24.452002] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G B 5.4.17-2102.200.0.0.20210106_0000.syzk #1
>>>> [ 24.452002] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
>>>> [ 24.452002] Call Trace:
>>>> [ 24.452002] dump_stack+0xd4/0x119
>>>> [ 24.452002] ? ibft_init+0x102/0xb8b
>>>> [ 24.452002] panic+0x28f/0x6e0
>>>> [ 24.452002] ? __warn_printk+0xe0/0xe0
>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>> [ 24.452002] ? add_taint+0x68/0xb3
>>>> [ 24.452002] ? add_taint+0x68/0xb3
>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>> [ 24.452002] end_report+0x4c/0x54
>>>> [ 24.452002] __kasan_report.cold.9+0x55/0x77
>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>> [ 24.452002] kasan_report+0x14/0x1b
>>>> [ 24.452002] __asan_report_load_n_noabort+0xf/0x11
>>>> [ 24.452002] ibft_init+0x134/0xb8b
>>>> [ 24.452002] ? dmi_sysfs_init+0x1a5/0x1a5
>>>> [ 24.452002] ? dmi_walk+0x72/0x89
>>>> [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
>>>> [ 24.452002] ? rvt_init_port+0x110/0x101
>>>> [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
>>>> [ 24.452002] do_one_initcall+0xc3/0x44d
>>>> [ 24.452002] ? perf_trace_initcall_level+0x410/0x405
>>>> [ 24.452002] kernel_init_freeable+0x551/0x673
>>>> [ 24.452002] ? start_kernel+0x94b/0x94b
>>>> [ 24.452002] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
>>>> [ 24.452002] ? __kasan_check_write+0x14/0x16
>>>> [ 24.452002] ? rest_init+0xe6/0xe6
>>>> [ 24.452002] kernel_init+0x16/0x1bd
>>>> [ 24.452002] ? rest_init+0xe6/0xe6
>>>> [ 24.452002] ret_from_fork+0x2b/0x36
>>>> [ 24.452002] Dumping ftrace buffer:
>>>> [ 24.452002] ---------------------------------
>>>> [ 24.452002] swapper/-1 1.... 24564337us : rdmaip_init: 2924: rdmaip_init: Active Bonding is DISABLED
>>>> [ 24.452002] ---------------------------------
>>>> [ 24.452002] Kernel Offset: disabled
>>>> [ 24.452002] Rebooting in 1 seconds..
>>>>
>>>> Why does KASAN think the address is freed? For that to happen that
>>>> memory should have been freed. I don't remember any similar false
>>>> positives from KASAN, so this looks a bit suspicious.
>>>>
>>>> I'm not sure why KASAN thinks the address is freed. There are other modules where KASAN/KCOV is disabled on boot.
>>>> Could this be for a similar reason?
>>> Most of these files are disabled because they cause recursion in
>>> instrumentation, or execute too early in bootstrap process (before
>>> kasan_init).
>>>
>>> Somehow the table pointer in ibft_init points to a freed page. I
>>> tracked it down to here:
>>> https://elixir.bootlin.com/linux/v5.4.17/source/drivers/acpi/acpica/tbutils.c#L399
>>> but I can't find where this table_desc->pointer comes from. Perhaps it
>> It is what the BIOS generated. It usually points to some memory
>> location in right under 4GB and the BIOS stashes the DSDT, iBFT, and
>> other tables in there.
>>
>>> uses some allocation method that's not supported by KASAN? However,
>>> it's the only such case that I've seen, so it's a bit weird. Could it
>>> use something like memblock_alloc? Or maybe that page was in fact
>>> freed?... Too bad KASAN does not print free stack for pages, maybe
>>> it's not too hard to do if CONFIG_PAGE_OWNER is enabled...
>> Hm, there is a comment in the acpi_get_table speaking about the
>> requirement of having a acpi_put_table and:
>>
>>
>> * DESCRIPTION: Finds and verifies an ACPI table. Table must be in the
>> * RSDT/XSDT.
>> * Note that an early stage acpi_get_table() call must be paired
>> * with an early stage acpi_put_table() call. otherwise the table
>> * pointer mapped by the early stage mapping implementation may be
>> * erroneously unmapped by the late stage unmapping implementation
>> * in an acpi_put_table() invoked during the late stage.
>> *
>>
>> Which would imply that I should use acpi_put_table in the error path
>> (see below a patch), but also copy the structure instead of depending
>> on ACPI keeping it mapped for me. I think.
> Hi Konrad,
>
> Thanks for looking into this.
> If ACPI unmaps this page, that would perfectly explain the KASAN report.
>
> George, does this patch eliminate the KASAN report for you?

Hi Dmitry,

No luck with the patch. Tried high level bisect instead. Here are the
results:

BUG: KASAN: use-after-free in ibft_init+0x134/0xc49

Bisect status:
v5.11-rc6 Sun Jan 31 13:50:09 2021 -0800     Failed
v5.11-rc1 Sun Dec 27 15:30:22 2020 -0800    Failed
v5.10 Sun Dec 13 14:41:30 2020 -0800           Failed
v5.10-rc6 Sun Nov 29 15:50:50 2020 -0800    Failed
v5.10-rc5 Sun Nov 22 15:36:08 2020 -0800    Failed
v5.10-rc4 Sun Nov 15 16:44:31 2020 -0800    Failed
v5.10-rc3 Sun Nov 8 16:10:16 2020 -0800      Failed
v5.10-rc2 Sun Nov 1 14:43:52 2020 -0800      Failed
v5.10-rc1 Sun Oct 25 15:14:11 2020 -0700     Failed
v5.9 Sun Oct 11 14:15:50 2020 -0700              OK - 10 reboots so far
w/o kasan failure

So, will look at what changed between v5.9 and v5.10-rc1

Failure is intermittent, so takes a lot of retries.

Thank you,
George

>
>
>> CC-ing Rafeal.
>>
>>
>> From c37da50fdfc62cd4f7b23562b55661478c90a17d Mon Sep 17 00:00:00 2001
>> From: Konrad Rzeszutek Wilk <[email protected]>
>> Date: Tue, 2 Feb 2021 17:28:28 +0000
>> Subject: [PATCH] ibft: Put ibft_addr back
>>
>> Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
>> ---
>> drivers/firmware/iscsi_ibft.c | 19 +++++++++++++------
>> 1 file changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/firmware/iscsi_ibft.c b/drivers/firmware/iscsi_ibft.c
>> index 7127a04..2a1a033 100644
>> --- a/drivers/firmware/iscsi_ibft.c
>> +++ b/drivers/firmware/iscsi_ibft.c
>> @@ -811,6 +811,10 @@ static void ibft_cleanup(void)
>> ibft_unregister();
>> iscsi_boot_destroy_kset(boot_kset);
>> }
>> + if (ibft_addr) {
>> + acpi_put_table((struct acpi_table_header *)ibft_addr);
>> + ibft_addr = NULL;
>> + }
>> }
>>
>> static void __exit ibft_exit(void)
>> @@ -835,13 +839,15 @@ static void __init acpi_find_ibft_region(void)
>> {
>> int i;
>> struct acpi_table_header *table = NULL;
>> + acpi_status status;
>>
>> if (acpi_disabled)
>> return;
>>
>> for (i = 0; i < ARRAY_SIZE(ibft_signs) && !ibft_addr; i++) {
>> - acpi_get_table(ibft_signs[i].sign, 0, &table);
>> - ibft_addr = (struct acpi_table_ibft *)table;
>> + status = acpi_get_table(ibft_signs[i].sign, 0, &table);
>> + if (ACPI_SUCCESS(status))
>> + ibft_addr = (struct acpi_table_ibft *)table;
>> }
>> }
>> #else
>> @@ -870,12 +876,13 @@ static int __init ibft_init(void)
>>
>> rc = ibft_check_device();
>> if (rc)
>> - return rc;
>> + goto out_free;
>>
>> boot_kset = iscsi_boot_create_kset("ibft");
>> - if (!boot_kset)
>> - return -ENOMEM;
>> -
>> + if (!boot_kset) {
>> + rc = -ENOMEM;
>> + goto out_free;
>> + }
>> /* Scan the IBFT for data and register the kobjects. */
>> rc = ibft_register_kobjects(ibft_addr);
>> if (rc)
>> --
>> 1.8.3.1
>>

2021-02-12 13:36:25

by George Kennedy

Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

On 2/10/2021 4:51 PM, George Kennedy wrote:
>
>
> On 2/3/2021 2:35 PM, Dmitry Vyukov wrote:
>> On Wed, Feb 3, 2021 at 8:29 PM Konrad Rzeszutek Wilk
>> <[email protected]> wrote:
>>> Hey Dmitry, Rafael, George, please see below..
>>>
>>> On Wed, Jan 27, 2021 at 10:10:07PM +0100, Dmitry Vyukov wrote:
>>>> On Wed, Jan 27, 2021 at 9:01 PM George Kennedy
>>>> <[email protected]> wrote:
>>>>> Hi Dmitry,
>>>>>
>>>>> On 1/27/2021 1:48 PM, Dmitry Vyukov wrote:
>>>>>
>>>>> On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
>>>>> <[email protected]> wrote:
>>>>>
>>>>> On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
>>>>>
>>>>> During boot of kernel with CONFIG_KASAN the following KASAN false
>>>>> positive failure will occur when ibft_init() reads the
>>>>> ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
>>>>>
>>>>> The ACPI iBFT table is not allocated, and the iscsi driver uses
>>>>> a pointer to it to calculate checksum, etc. KASAN complains
>>>>> about this pointer with use-after-free, which this is not.
>>>>>
>>>>> Andrey, Alexander, Dmitry,
>>>>>
>>>>> I think this is the right way for this, but was wondering if you have
>>>>> other suggestions?
>>>>>
>>>>> Thanks!
>>>>>
>>>>> Hi George, Konrad,
>>>>>
>>>>> Please provide a sample KASAN report and kernel version to match
>>>>> line numbers.
>>>>>
>>>>> 5.4.17-2102.200.0.0.20210106_0000
>>>>>
>>>>> [   24.413536] iBFT detected.
>>>>> [   24.414074]
>>>>> ==================================================================
>>>>> [   24.407342] BUG: KASAN: use-after-free in ibft_init+0x134/0xb8b
>>>>> [   24.407342] Read of size 4 at addr ffff8880be452004 by task
>>>>> swapper/0/1
>>>>> [   24.407342]
>>>>> [   24.407342] CPU: 1 PID: 1 Comm: swapper/0 Not tainted
>>>>> 5.4.17-2102.200.0.0.20210106_0000.syzk #1
>>>>> [   24.407342] Hardware name: QEMU Standard PC (i440FX + PIIX,
>>>>> 1996), BIOS 0.0.0 02/06/2015
>>>>> [   24.407342] Call Trace:
>>>>> [   24.407342]  dump_stack+0xd4/0x119
>>>>> [   24.407342]  ? ibft_init+0x134/0xb8b
>>>>> [   24.407342] print_address_description.constprop.6+0x20/0x220
>>>>> [   24.407342]  ? ibft_init+0x134/0xb8b
>>>>> [   24.407342]  ? ibft_init+0x134/0xb8b
>>>>> [   24.407342]  __kasan_report.cold.9+0x37/0x77
>>>>> [   24.407342]  ? ibft_init+0x134/0xb8b
>>>>> [   24.407342]  kasan_report+0x14/0x1b
>>>>> [   24.407342]  __asan_report_load_n_noabort+0xf/0x11
>>>>> [   24.407342]  ibft_init+0x134/0xb8b
>>>>> [   24.407342]  ? dmi_sysfs_init+0x1a5/0x1a5
>>>>> [   24.407342]  ? dmi_walk+0x72/0x89
>>>>> [   24.407342]  ? ibft_check_initiator_for+0x159/0x159
>>>>> [   24.407342]  ? rvt_init_port+0x110/0x101
>>>>> [   24.407342]  ? ibft_check_initiator_for+0x159/0x159
>>>>> [   24.407342]  do_one_initcall+0xc3/0x44d
>>>>> [   24.407342]  ? perf_trace_initcall_level+0x410/0x405
>>>>> [   24.407342]  kernel_init_freeable+0x551/0x673
>>>>> [   24.407342]  ? start_kernel+0x94b/0x94b
>>>>> [   24.407342]  ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
>>>>> [   24.407342]  ? __kasan_check_write+0x14/0x16
>>>>> [   24.407342]  ? rest_init+0xe6/0xe6
>>>>> [   24.407342]  kernel_init+0x16/0x1bd
>>>>> [   24.407342]  ? rest_init+0xe6/0xe6
>>>>> [   24.407342]  ret_from_fork+0x2b/0x36
>>>>> [   24.407342]
>>>>> [   24.407342] The buggy address belongs to the page:
>>>>> [   24.407342] page:ffffea0002f91480 refcount:0 mapcount:0
>>>>> mapping:0000000000000000 index:0x1
>>>>> [   24.407342] flags: 0xfffffc0000000()
>>>>> [   24.407342] raw: 000fffffc0000000 ffffea0002fca588
>>>>> ffffea0002fb1a88 0000000000000000
>>>>> [   24.407342] raw: 0000000000000001 0000000000000000
>>>>> 00000000ffffffff 0000000000000000
>>>>> [   24.407342] page dumped because: kasan: bad access detected
>>>>> [   24.407342]
>>>>> [   24.407342] Memory state around the buggy address:
>>>>> [   24.407342]  ffff8880be451f00: ff ff ff ff ff ff ff ff ff ff ff
>>>>> ff ff ff ff ff
>>>>> [   24.407342]  ffff8880be451f80: ff ff ff ff ff ff ff ff ff ff ff
>>>>> ff ff ff ff ff
>>>>> [   24.407342] >ffff8880be452000: ff ff ff ff ff ff ff ff ff ff ff
>>>>> ff ff ff ff ff
>>>>> [   24.407342]                    ^
>>>>> [   24.407342]  ffff8880be452080: ff ff ff ff ff ff ff ff ff ff ff
>>>>> ff ff ff ff ff
>>>>> [   24.407342]  ffff8880be452100: ff ff ff ff ff ff ff ff ff ff ff
>>>>> ff ff ff ff ff
>>>>> [   24.407342]
>>>>> ==================================================================
>>>>> [   24.407342] Disabling lock debugging due to kernel taint
>>>>> [   24.451021] Kernel panic - not syncing: panic_on_warn set ...
>>>>> [   24.452002] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G B
>>>>> 5.4.17-2102.200.0.0.20210106_0000.syzk #1
>>>>> [   24.452002] Hardware name: QEMU Standard PC (i440FX + PIIX,
>>>>> 1996), BIOS 0.0.0 02/06/2015
>>>>> [   24.452002] Call Trace:
>>>>> [   24.452002]  dump_stack+0xd4/0x119
>>>>> [   24.452002]  ? ibft_init+0x102/0xb8b
>>>>> [   24.452002]  panic+0x28f/0x6e0
>>>>> [   24.452002]  ? __warn_printk+0xe0/0xe0
>>>>> [   24.452002]  ? ibft_init+0x134/0xb8b
>>>>> [   24.452002]  ? add_taint+0x68/0xb3
>>>>> [   24.452002]  ? add_taint+0x68/0xb3
>>>>> [   24.452002]  ? ibft_init+0x134/0xb8b
>>>>> [   24.452002]  ? ibft_init+0x134/0xb8b
>>>>> [   24.452002]  end_report+0x4c/0x54
>>>>> [   24.452002]  __kasan_report.cold.9+0x55/0x77
>>>>> [   24.452002]  ? ibft_init+0x134/0xb8b
>>>>> [   24.452002]  kasan_report+0x14/0x1b
>>>>> [   24.452002]  __asan_report_load_n_noabort+0xf/0x11
>>>>> [   24.452002]  ibft_init+0x134/0xb8b
>>>>> [   24.452002]  ? dmi_sysfs_init+0x1a5/0x1a5
>>>>> [   24.452002]  ? dmi_walk+0x72/0x89
>>>>> [   24.452002]  ? ibft_check_initiator_for+0x159/0x159
>>>>> [   24.452002]  ? rvt_init_port+0x110/0x101
>>>>> [   24.452002]  ? ibft_check_initiator_for+0x159/0x159
>>>>> [   24.452002]  do_one_initcall+0xc3/0x44d
>>>>> [   24.452002]  ? perf_trace_initcall_level+0x410/0x405
>>>>> [   24.452002]  kernel_init_freeable+0x551/0x673
>>>>> [   24.452002]  ? start_kernel+0x94b/0x94b
>>>>> [   24.452002]  ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
>>>>> [   24.452002]  ? __kasan_check_write+0x14/0x16
>>>>> [   24.452002]  ? rest_init+0xe6/0xe6
>>>>> [   24.452002]  kernel_init+0x16/0x1bd
>>>>> [   24.452002]  ? rest_init+0xe6/0xe6
>>>>> [   24.452002]  ret_from_fork+0x2b/0x36
>>>>> [   24.452002] Dumping ftrace buffer:
>>>>> [   24.452002] ---------------------------------
>>>>> [   24.452002] swapper/-1         1.... 24564337us : rdmaip_init:
>>>>> 2924: rdmaip_init: Active Bonding is DISABLED
>>>>> [   24.452002] ---------------------------------
>>>>> [   24.452002] Kernel Offset: disabled
>>>>> [   24.452002] Rebooting in 1 seconds..
>>>>>
>>>>> Why does KASAN think the address is freed? For that to happen that
>>>>> memory should have been freed. I don't remember any similar false
>>>>> positives from KASAN, so this looks a bit suspicious.
>>>>>
>>>>> I'm not sure why KASAN thinks the address is freed. There are
>>>>> other modules where KASAN/KCOV is disabled on boot.
>>>>> Could this be for a similar reason?
>>>> Most of these files are disabled because they cause recursion in
>>>> instrumentation, or execute too early in bootstrap process (before
>>>> kasan_init).
>>>>
>>>> Somehow the table pointer in ibft_init points to a freed page. I
>>>> tracked it down to here:
>>>> https://elixir.bootlin.com/linux/v5.4.17/source/drivers/acpi/acpica/tbutils.c#L399
>>>>
>>>> but I can't find where this table_desc->pointer comes from. Perhaps it
>>> It is what the BIOS generated. It usually points to some memory
>>> location in right under 4GB and the BIOS stashes the DSDT, iBFT, and
>>> other tables in there.
>>>
>>>> uses some allocation method that's not supported by KASAN? However,
>>>> it's the only such case that I've seen, so it's a bit weird. Could it
>>>> use something like memblock_alloc? Or maybe that page was in fact
>>>> freed?... Too bad KASAN does not print free stack for pages, maybe
>>>> it's not too hard to do if CONFIG_PAGE_OWNER is enabled...
>>> Hm, there is a comment in the acpi_get_table speaking about the
>>> requirement of having a acpi_put_table and:
>>>
>>>
>>>   * DESCRIPTION: Finds and verifies an ACPI table. Table must be in the
>>>   *              RSDT/XSDT.
>>>   *              Note that an early stage acpi_get_table() call must
>>> be paired
>>>   *              with an early stage acpi_put_table() call.
>>> otherwise the table
>>>   *              pointer mapped by the early stage mapping
>>> implementation may be
>>>   *              erroneously unmapped by the late stage unmapping
>>> implementation
>>>   *              in an acpi_put_table() invoked during the late stage.
>>>   *
>>>
>>> Which would imply that I should use acpi_put_table in the error path
>>> (see below a patch), but also copy the structure instead of depending
>>> on ACPI keeping it mapped for me. I think.
>> Hi Konrad,
>>
>> Thanks for looking into this.
>> If ACPI unmaps this page, that would perfectly explain the KASAN report.
>>
>> George, does this patch eliminate the KASAN report for you?
>
> Hi Dmitry,
>
> No luck with the patch. Tried high level bisect instead. Here are the
> results:
>
> BUG: KASAN: use-after-free in ibft_init+0x134/0xc49
>
> Bisect status:
> v5.11-rc6 Sun Jan 31 13:50:09 2021 -0800     Failed
> v5.11-rc1 Sun Dec 27 15:30:22 2020 -0800    Failed
> v5.10 Sun Dec 13 14:41:30 2020 -0800           Failed
> v5.10-rc6 Sun Nov 29 15:50:50 2020 -0800    Failed
> v5.10-rc5 Sun Nov 22 15:36:08 2020 -0800    Failed
> v5.10-rc4 Sun Nov 15 16:44:31 2020 -0800    Failed
> v5.10-rc3 Sun Nov 8 16:10:16 2020 -0800      Failed
> v5.10-rc2 Sun Nov 1 14:43:52 2020 -0800      Failed
> v5.10-rc1 Sun Oct 25 15:14:11 2020 -0700     Failed
> v5.9 Sun Oct 11 14:15:50 2020 -0700              OK - 10 reboots so
> far w/o kasan failure
>
> So, will look at what changed between v5.9 and v5.10-rc1

git bisect has identified the following as the offending commit:

2020-10-16 [email protected] - 7fef431 2020-10-15 David
Hildenbrand mm/page_alloc: place pages to tail in __free_pages_core()

Here's the commit that follows the above:

2020-10-16 [email protected] - 293ffa5 2020-10-15 David
Hildenbrand mm/page_alloc: move pages to tail in move_to_free_list()

With HEAD=7fef431 the KASAN crash occurs.
With HEAD=293ffa5 no crash.

With latest upstream (HEAD=dcc0b49) now getting this:

[    1.759763] BUG: unable to handle page fault for address:
ffff8880be453000
[    1.761100] #PF: supervisor read access in kernel mode
[    1.762106] #PF: error_code(0x0000) - not-present page
[    1.763114] PGD 28c01067 P4D 28c01067 PUD 13fb01067 PMD 13f90e067 PTE
800fffff41bac060
[    1.764672] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
[    1.765731] CPU: 0 PID: 0 Comm: swapper/0 Not tainted
5.11.0-rc7-dcc0b49 #39
[    1.767103] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 0.0.0 02/06/2015
[    1.768665] RIP: 0010:acpi_tb_verify_checksum
(drivers/acpi/acpica/tbprint.c:161)
[    1.773301] RSP: 0000:ffffffff8fe07c78 EFLAGS: 00010246
[    1.774330] RAX: 0000000000000003 RBX: ffff8880be453000 RCX:
ffffffff839ab92c
[    1.775718] RDX: 1ffff11017c8a600 RSI: ffffffff8fe3dec0 RDI:
0000000000000002
[    1.777099] RBP: ffffffff8fe07c90 R08: 0000000000000000 R09:
fffffbfff212ebfd
[    1.778479] R10: ffffffff90975fe7 R11: fffffbfff212ebfc R12:
0000000000000800
[    1.779864] R13: 0000000000000800 R14: dffffc0000000000 R15:
0000000000000000
[    1.781245] FS:  0000000000000000(0000) GS:ffff88810a400000(0000)
knlGS:0000000000000000
[    1.782819] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    1.783941] CR2: ffff8880be453000 CR3: 0000000024e30000 CR4:
00000000000006b0
[    1.785325] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[    1.786709] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[    1.788094] Call Trace:
[    1.788595] acpi_tb_verify_temp_table (drivers/acpi/acpica/tbdata.c:499)
[    1.789546] ? acpi_tb_validate_temp_table
(drivers/acpi/acpica/tbdata.c:469)
[    1.790536] ? __sanitizer_cov_trace_pc (kernel/kcov.c:197)
[    1.791474] ? write_comp_data (kernel/kcov.c:218)
[    1.792263] ? write_comp_data (kernel/kcov.c:218)
[    1.793049] ? __sanitizer_cov_trace_pc (kernel/kcov.c:197)
[    1.793983] ? write_comp_data (kernel/kcov.c:218)
[    1.794766] acpi_reallocate_root_table
(drivers/acpi/acpica/tbxface.c:182)
[    1.795736] ? acpi_tb_parse_root_table
(drivers/acpi/acpica/tbxface.c:134)
[    1.796706] ? write_comp_data (kernel/kcov.c:218)
[    1.797488] ? __sanitizer_cov_trace_pc (kernel/kcov.c:197)
[    1.798422] acpi_early_init (drivers/acpi/bus.c:1050)
[    1.799211] start_kernel (init/main.c:1023)
[    1.799955] x86_64_start_reservations (arch/x86/kernel/head64.c:526)
[    1.800875] x86_64_start_kernel (arch/x86/kernel/head64.c:507)
[    1.801699] secondary_startup_64_no_verify
(arch/x86/kernel/head_64.S:283)
[    1.802709] Modules linked in:
[    1.803324] Dumping ftrace buffer:
[    1.804003]    (ftrace buffer empty)
[    1.804707] CR2: ffff8880be453000
[    1.805369] ---[ end trace fab88542288c30b6 ]---
[    1.806272] RIP: 0010:acpi_tb_verify_checksum
(drivers/acpi/acpica/tbprint.c:161)
[ 1.807325] Code: da b8 ff ff 37 00 48 c1 e0 2a 48 c1 ea 03 8a 14 02 48
89 d8 83 e0 07 83 c0 03 38 d0 7c 0c 84 d2 74 08 48 89 df e8 c6 f8 1e fe
<44> 8b 23 bf 53 33 50 54 44 89 e6 e8 f6 84 db fd 41 81 fc 53 33 50
[    1.810904] RSP: 0000:ffffffff8fe07c78 EFLAGS: 00010246
[    1.811930] RAX: 0000000000000003 RBX: ffff8880be453000 RCX:
ffffffff839ab92c
[    1.813312] RDX: 1ffff11017c8a600 RSI: ffffffff8fe3dec0 RDI:
0000000000000002
[    1.814701] RBP: ffffffff8fe07c90 R08: 0000000000000000 R09:
fffffbfff212ebfd
[    1.816078] R10: ffffffff90975fe7 R11: fffffbfff212ebfc R12:
0000000000000800
[    1.817458] R13: 0000000000000800 R14: dffffc0000000000 R15:
0000000000000000
[    1.818841] FS:  0000000000000000(0000) GS:ffff88810a400000(0000)
knlGS:0000000000000000
[    1.820406] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    1.821529] CR2: ffff8880be453000 CR3: 0000000024e30000 CR4:
00000000000006b0
[    1.822918] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[    1.824299] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[    1.825680] Kernel panic - not syncing: Fatal exception
[    1.827454] Dumping ftrace buffer:
[    1.828122]    (ftrace buffer empty)
[    1.828821] Rebooting in 1 seconds..

Thank you,
George

>
> Failure is intermittent, so takes a lot of retries.
>
> Thank you,
> George
>
>>
>>
>>> CC-ing Rafeal.
>>>
>>>
>>>  From c37da50fdfc62cd4f7b23562b55661478c90a17d Mon Sep 17 00:00:00 2001
>>> From: Konrad Rzeszutek Wilk <[email protected]>
>>> Date: Tue, 2 Feb 2021 17:28:28 +0000
>>> Subject: [PATCH] ibft: Put ibft_addr back
>>>
>>> Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
>>> ---
>>>   drivers/firmware/iscsi_ibft.c | 19 +++++++++++++------
>>>   1 file changed, 13 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/firmware/iscsi_ibft.c
>>> b/drivers/firmware/iscsi_ibft.c
>>> index 7127a04..2a1a033 100644
>>> --- a/drivers/firmware/iscsi_ibft.c
>>> +++ b/drivers/firmware/iscsi_ibft.c
>>> @@ -811,6 +811,10 @@ static void ibft_cleanup(void)
>>>                  ibft_unregister();
>>>                  iscsi_boot_destroy_kset(boot_kset);
>>>          }
>>> +       if (ibft_addr) {
>>> +               acpi_put_table((struct acpi_table_header *)ibft_addr);
>>> +               ibft_addr = NULL;
>>> +       }
>>>   }
>>>
>>>   static void __exit ibft_exit(void)
>>> @@ -835,13 +839,15 @@ static void __init acpi_find_ibft_region(void)
>>>   {
>>>          int i;
>>>          struct acpi_table_header *table = NULL;
>>> +       acpi_status status;
>>>
>>>          if (acpi_disabled)
>>>                  return;
>>>
>>>          for (i = 0; i < ARRAY_SIZE(ibft_signs) && !ibft_addr; i++) {
>>> -               acpi_get_table(ibft_signs[i].sign, 0, &table);
>>> -               ibft_addr = (struct acpi_table_ibft *)table;
>>> +               status = acpi_get_table(ibft_signs[i].sign, 0, &table);
>>> +               if (ACPI_SUCCESS(status))
>>> +                       ibft_addr = (struct acpi_table_ibft *)table;
>>>          }
>>>   }
>>>   #else
>>> @@ -870,12 +876,13 @@ static int __init ibft_init(void)
>>>
>>>                  rc = ibft_check_device();
>>>                  if (rc)
>>> -                       return rc;
>>> +                       goto out_free;
>>>
>>>                  boot_kset = iscsi_boot_create_kset("ibft");
>>> -               if (!boot_kset)
>>> -                       return -ENOMEM;
>>> -
>>> +               if (!boot_kset) {
>>> +                       rc = -ENOMEM;
>>> +                       goto out_free;
>>> +               }
>>>                  /* Scan the IBFT for data and register the
>>> kobjects. */
>>>                  rc = ibft_register_kobjects(ibft_addr);
>>>                  if (rc)
>>> --
>>> 1.8.3.1
>>>
>

2021-02-12 13:56:02

by Dmitry Vyukov

Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

On Fri, Feb 12, 2021 at 2:31 PM George Kennedy
<[email protected]> wrote:
> On 2/10/2021 4:51 PM, George Kennedy wrote:
> > On 2/3/2021 2:35 PM, Dmitry Vyukov wrote:
> >> On Wed, Feb 3, 2021 at 8:29 PM Konrad Rzeszutek Wilk
> >> <[email protected]> wrote:
> >>> Hey Dmitry, Rafael, George, please see below..
> >>>
> >>> On Wed, Jan 27, 2021 at 10:10:07PM +0100, Dmitry Vyukov wrote:
> >>>> On Wed, Jan 27, 2021 at 9:01 PM George Kennedy
> >>>> <[email protected]> wrote:
> >>>>> Hi Dmitry,
> >>>>>
> >>>>> On 1/27/2021 1:48 PM, Dmitry Vyukov wrote:
> >>>>>
> >>>>> On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
> >>>>> <[email protected]> wrote:
> >>>>>
> >>>>> On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
> >>>>>
> >>>>> During boot of kernel with CONFIG_KASAN the following KASAN false
> >>>>> positive failure will occur when ibft_init() reads the
> >>>>> ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
> >>>>>
> >>>>> The ACPI iBFT table is not allocated, and the iscsi driver uses
> >>>>> a pointer to it to calculate checksum, etc. KASAN complains
> >>>>> about this pointer with use-after-free, which this is not.
> >>>>>
> >>>>> Andrey, Alexander, Dmitry,
> >>>>>
> >>>>> I think this is the right way for this, but was wondering if you have
> >>>>> other suggestions?
> >>>>>
> >>>>> Thanks!
> >>>>>
> >>>>> Hi George, Konrad,
> >>>>>
> >>>>> Please provide a sample KASAN report and kernel version to match
> >>>>> line numbers.
> >>>>>
> >>>>> 5.4.17-2102.200.0.0.20210106_0000
> >>>>>
> >>>>> [ 24.413536] iBFT detected.
> >>>>> [ 24.414074]
> >>>>> ==================================================================
> >>>>> [ 24.407342] BUG: KASAN: use-after-free in ibft_init+0x134/0xb8b
> >>>>> [ 24.407342] Read of size 4 at addr ffff8880be452004 by task
> >>>>> swapper/0/1
> >>>>> [ 24.407342]
> >>>>> [ 24.407342] CPU: 1 PID: 1 Comm: swapper/0 Not tainted
> >>>>> 5.4.17-2102.200.0.0.20210106_0000.syzk #1
> >>>>> [ 24.407342] Hardware name: QEMU Standard PC (i440FX + PIIX,
> >>>>> 1996), BIOS 0.0.0 02/06/2015
> >>>>> [ 24.407342] Call Trace:
> >>>>> [ 24.407342] dump_stack+0xd4/0x119
> >>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
> >>>>> [ 24.407342] print_address_description.constprop.6+0x20/0x220
> >>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
> >>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
> >>>>> [ 24.407342] __kasan_report.cold.9+0x37/0x77
> >>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
> >>>>> [ 24.407342] kasan_report+0x14/0x1b
> >>>>> [ 24.407342] __asan_report_load_n_noabort+0xf/0x11
> >>>>> [ 24.407342] ibft_init+0x134/0xb8b
> >>>>> [ 24.407342] ? dmi_sysfs_init+0x1a5/0x1a5
> >>>>> [ 24.407342] ? dmi_walk+0x72/0x89
> >>>>> [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
> >>>>> [ 24.407342] ? rvt_init_port+0x110/0x101
> >>>>> [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
> >>>>> [ 24.407342] do_one_initcall+0xc3/0x44d
> >>>>> [ 24.407342] ? perf_trace_initcall_level+0x410/0x405
> >>>>> [ 24.407342] kernel_init_freeable+0x551/0x673
> >>>>> [ 24.407342] ? start_kernel+0x94b/0x94b
> >>>>> [ 24.407342] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
> >>>>> [ 24.407342] ? __kasan_check_write+0x14/0x16
> >>>>> [ 24.407342] ? rest_init+0xe6/0xe6
> >>>>> [ 24.407342] kernel_init+0x16/0x1bd
> >>>>> [ 24.407342] ? rest_init+0xe6/0xe6
> >>>>> [ 24.407342] ret_from_fork+0x2b/0x36
> >>>>> [ 24.407342]
> >>>>> [ 24.407342] The buggy address belongs to the page:
> >>>>> [ 24.407342] page:ffffea0002f91480 refcount:0 mapcount:0
> >>>>> mapping:0000000000000000 index:0x1
> >>>>> [ 24.407342] flags: 0xfffffc0000000()
> >>>>> [ 24.407342] raw: 000fffffc0000000 ffffea0002fca588
> >>>>> ffffea0002fb1a88 0000000000000000
> >>>>> [ 24.407342] raw: 0000000000000001 0000000000000000
> >>>>> 00000000ffffffff 0000000000000000
> >>>>> [ 24.407342] page dumped because: kasan: bad access detected
> >>>>> [ 24.407342]
> >>>>> [ 24.407342] Memory state around the buggy address:
> >>>>> [ 24.407342] ffff8880be451f00: ff ff ff ff ff ff ff ff ff ff ff
> >>>>> ff ff ff ff ff
> >>>>> [ 24.407342] ffff8880be451f80: ff ff ff ff ff ff ff ff ff ff ff
> >>>>> ff ff ff ff ff
> >>>>> [ 24.407342] >ffff8880be452000: ff ff ff ff ff ff ff ff ff ff ff
> >>>>> ff ff ff ff ff
> >>>>> [ 24.407342] ^
> >>>>> [ 24.407342] ffff8880be452080: ff ff ff ff ff ff ff ff ff ff ff
> >>>>> ff ff ff ff ff
> >>>>> [ 24.407342] ffff8880be452100: ff ff ff ff ff ff ff ff ff ff ff
> >>>>> ff ff ff ff ff
> >>>>> [ 24.407342]
> >>>>> ==================================================================
> >>>>> [ 24.407342] Disabling lock debugging due to kernel taint
> >>>>> [ 24.451021] Kernel panic - not syncing: panic_on_warn set ...
> >>>>> [ 24.452002] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G B
> >>>>> 5.4.17-2102.200.0.0.20210106_0000.syzk #1
> >>>>> [ 24.452002] Hardware name: QEMU Standard PC (i440FX + PIIX,
> >>>>> 1996), BIOS 0.0.0 02/06/2015
> >>>>> [ 24.452002] Call Trace:
> >>>>> [ 24.452002] dump_stack+0xd4/0x119
> >>>>> [ 24.452002] ? ibft_init+0x102/0xb8b
> >>>>> [ 24.452002] panic+0x28f/0x6e0
> >>>>> [ 24.452002] ? __warn_printk+0xe0/0xe0
> >>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
> >>>>> [ 24.452002] ? add_taint+0x68/0xb3
> >>>>> [ 24.452002] ? add_taint+0x68/0xb3
> >>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
> >>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
> >>>>> [ 24.452002] end_report+0x4c/0x54
> >>>>> [ 24.452002] __kasan_report.cold.9+0x55/0x77
> >>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
> >>>>> [ 24.452002] kasan_report+0x14/0x1b
> >>>>> [ 24.452002] __asan_report_load_n_noabort+0xf/0x11
> >>>>> [ 24.452002] ibft_init+0x134/0xb8b
> >>>>> [ 24.452002] ? dmi_sysfs_init+0x1a5/0x1a5
> >>>>> [ 24.452002] ? dmi_walk+0x72/0x89
> >>>>> [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
> >>>>> [ 24.452002] ? rvt_init_port+0x110/0x101
> >>>>> [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
> >>>>> [ 24.452002] do_one_initcall+0xc3/0x44d
> >>>>> [ 24.452002] ? perf_trace_initcall_level+0x410/0x405
> >>>>> [ 24.452002] kernel_init_freeable+0x551/0x673
> >>>>> [ 24.452002] ? start_kernel+0x94b/0x94b
> >>>>> [ 24.452002] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
> >>>>> [ 24.452002] ? __kasan_check_write+0x14/0x16
> >>>>> [ 24.452002] ? rest_init+0xe6/0xe6
> >>>>> [ 24.452002] kernel_init+0x16/0x1bd
> >>>>> [ 24.452002] ? rest_init+0xe6/0xe6
> >>>>> [ 24.452002] ret_from_fork+0x2b/0x36
> >>>>> [ 24.452002] Dumping ftrace buffer:
> >>>>> [ 24.452002] ---------------------------------
> >>>>> [ 24.452002] swapper/-1 1.... 24564337us : rdmaip_init:
> >>>>> 2924: rdmaip_init: Active Bonding is DISABLED
> >>>>> [ 24.452002] ---------------------------------
> >>>>> [ 24.452002] Kernel Offset: disabled
> >>>>> [ 24.452002] Rebooting in 1 seconds..
> >>>>>
> >>>>> Why does KASAN think the address is freed? For that to happen that
> >>>>> memory should have been freed. I don't remember any similar false
> >>>>> positives from KASAN, so this looks a bit suspicious.
> >>>>>
> >>>>> I'm not sure why KASAN thinks the address is freed. There are
> >>>>> other modules where KASAN/KCOV is disabled on boot.
> >>>>> Could this be for a similar reason?
> >>>> Most of these files are disabled because they cause recursion in
> >>>> instrumentation, or execute too early in bootstrap process (before
> >>>> kasan_init).
> >>>>
> >>>> Somehow the table pointer in ibft_init points to a freed page. I
> >>>> tracked it down to here:
> >>>> https://elixir.bootlin.com/linux/v5.4.17/source/drivers/acpi/acpica/tbutils.c#L399
> >>>>
> >>>> but I can't find where this table_desc->pointer comes from. Perhaps it
> >>> It is what the BIOS generated. It usually points to some memory
> >>> location in right under 4GB and the BIOS stashes the DSDT, iBFT, and
> >>> other tables in there.
> >>>
> >>>> uses some allocation method that's not supported by KASAN? However,
> >>>> it's the only such case that I've seen, so it's a bit weird. Could it
> >>>> use something like memblock_alloc? Or maybe that page was in fact
> >>>> freed?... Too bad KASAN does not print free stack for pages, maybe
> >>>> it's not too hard to do if CONFIG_PAGE_OWNER is enabled...
> >>> Hm, there is a comment in the acpi_get_table speaking about the
> >>> requirement of having a acpi_put_table and:
> >>>
> >>>
> >>> * DESCRIPTION: Finds and verifies an ACPI table. Table must be in the
> >>> * RSDT/XSDT.
> >>> * Note that an early stage acpi_get_table() call must
> >>> be paired
> >>> * with an early stage acpi_put_table() call.
> >>> otherwise the table
> >>> * pointer mapped by the early stage mapping
> >>> implementation may be
> >>> * erroneously unmapped by the late stage unmapping
> >>> implementation
> >>> * in an acpi_put_table() invoked during the late stage.
> >>> *
> >>>
> >>> Which would imply that I should use acpi_put_table in the error path
> >>> (see below a patch), but also copy the structure instead of depending
> >>> on ACPI keeping it mapped for me. I think.
> >> Hi Konrad,
> >>
> >> Thanks for looking into this.
> >> If ACPI unmaps this page, that would perfectly explain the KASAN report.
> >>
> >> George, does this patch eliminate the KASAN report for you?
> >
> > Hi Dmitry,
> >
> > No luck with the patch. Tried high level bisect instead. Here are the
> > results:
> >
> > BUG: KASAN: use-after-free in ibft_init+0x134/0xc49
> >
> > Bisect status:
> > v5.11-rc6 Sun Jan 31 13:50:09 2021 -0800 Failed
> > v5.11-rc1 Sun Dec 27 15:30:22 2020 -0800 Failed
> > v5.10 Sun Dec 13 14:41:30 2020 -0800 Failed
> > v5.10-rc6 Sun Nov 29 15:50:50 2020 -0800 Failed
> > v5.10-rc5 Sun Nov 22 15:36:08 2020 -0800 Failed
> > v5.10-rc4 Sun Nov 15 16:44:31 2020 -0800 Failed
> > v5.10-rc3 Sun Nov 8 16:10:16 2020 -0800 Failed
> > v5.10-rc2 Sun Nov 1 14:43:52 2020 -0800 Failed
> > v5.10-rc1 Sun Oct 25 15:14:11 2020 -0700 Failed
> > v5.9 Sun Oct 11 14:15:50 2020 -0700 OK - 10 reboots so
> > far w/o kasan failure
> >
> > So, will look at what changed between v5.9 and v5.10-rc1
>
> git bisect has identified the following as the offending commit:
>
> 2020-10-16 [email protected] - 7fef431 2020-10-15 David
> Hildenbrand mm/page_alloc: place pages to tail in __free_pages_core()

I think this suggests that this is a real use-after-free and the
page_alloc change just exposed a latent bug.

> Here's the commit that follows the above:
>
> 2020-10-16 [email protected] - 293ffa5 2020-10-15 David
> Hildenbrand mm/page_alloc: move pages to tail in move_to_free_list()
>
> With HEAD=7fef431 the KASAN crash occurs.
> With HEAD=293ffa5 no crash.
>
> With latest upstream (HEAD=dcc0b49) now getting this:
>
> [ 1.759763] BUG: unable to handle page fault for address:
> ffff8880be453000
> [ 1.761100] #PF: supervisor read access in kernel mode
> [ 1.762106] #PF: error_code(0x0000) - not-present page
> [ 1.763114] PGD 28c01067 P4D 28c01067 PUD 13fb01067 PMD 13f90e067 PTE
> 800fffff41bac060
> [ 1.764672] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
> [ 1.765731] CPU: 0 PID: 0 Comm: swapper/0 Not tainted
> 5.11.0-rc7-dcc0b49 #39
> [ 1.767103] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS 0.0.0 02/06/2015
> [ 1.768665] RIP: 0010:acpi_tb_verify_checksum
> (drivers/acpi/acpica/tbprint.c:161)
> [ 1.773301] RSP: 0000:ffffffff8fe07c78 EFLAGS: 00010246
> [ 1.774330] RAX: 0000000000000003 RBX: ffff8880be453000 RCX:
> ffffffff839ab92c
> [ 1.775718] RDX: 1ffff11017c8a600 RSI: ffffffff8fe3dec0 RDI:
> 0000000000000002
> [ 1.777099] RBP: ffffffff8fe07c90 R08: 0000000000000000 R09:
> fffffbfff212ebfd
> [ 1.778479] R10: ffffffff90975fe7 R11: fffffbfff212ebfc R12:
> 0000000000000800
> [ 1.779864] R13: 0000000000000800 R14: dffffc0000000000 R15:
> 0000000000000000
> [ 1.781245] FS: 0000000000000000(0000) GS:ffff88810a400000(0000)
> knlGS:0000000000000000
> [ 1.782819] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 1.783941] CR2: ffff8880be453000 CR3: 0000000024e30000 CR4:
> 00000000000006b0
> [ 1.785325] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> 0000000000000000
> [ 1.786709] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> 0000000000000400
> [ 1.788094] Call Trace:
> [ 1.788595] acpi_tb_verify_temp_table (drivers/acpi/acpica/tbdata.c:499)
> [ 1.789546] ? acpi_tb_validate_temp_table
> (drivers/acpi/acpica/tbdata.c:469)
> [ 1.790536] ? __sanitizer_cov_trace_pc (kernel/kcov.c:197)
> [ 1.791474] ? write_comp_data (kernel/kcov.c:218)
> [ 1.792263] ? write_comp_data (kernel/kcov.c:218)
> [ 1.793049] ? __sanitizer_cov_trace_pc (kernel/kcov.c:197)
> [ 1.793983] ? write_comp_data (kernel/kcov.c:218)
> [ 1.794766] acpi_reallocate_root_table
> (drivers/acpi/acpica/tbxface.c:182)
> [ 1.795736] ? acpi_tb_parse_root_table
> (drivers/acpi/acpica/tbxface.c:134)
> [ 1.796706] ? write_comp_data (kernel/kcov.c:218)
> [ 1.797488] ? __sanitizer_cov_trace_pc (kernel/kcov.c:197)
> [ 1.798422] acpi_early_init (drivers/acpi/bus.c:1050)
> [ 1.799211] start_kernel (init/main.c:1023)
> [ 1.799955] x86_64_start_reservations (arch/x86/kernel/head64.c:526)
> [ 1.800875] x86_64_start_kernel (arch/x86/kernel/head64.c:507)
> [ 1.801699] secondary_startup_64_no_verify
> (arch/x86/kernel/head_64.S:283)
> [ 1.802709] Modules linked in:
> [ 1.803324] Dumping ftrace buffer:
> [ 1.804003] (ftrace buffer empty)
> [ 1.804707] CR2: ffff8880be453000
> [ 1.805369] ---[ end trace fab88542288c30b6 ]---
> [ 1.806272] RIP: 0010:acpi_tb_verify_checksum
> (drivers/acpi/acpica/tbprint.c:161)
> [ 1.807325] Code: da b8 ff ff 37 00 48 c1 e0 2a 48 c1 ea 03 8a 14 02 48
> 89 d8 83 e0 07 83 c0 03 38 d0 7c 0c 84 d2 74 08 48 89 df e8 c6 f8 1e fe
> <44> 8b 23 bf 53 33 50 54 44 89 e6 e8 f6 84 db fd 41 81 fc 53 33 50
> [ 1.810904] RSP: 0000:ffffffff8fe07c78 EFLAGS: 00010246
> [ 1.811930] RAX: 0000000000000003 RBX: ffff8880be453000 RCX:
> ffffffff839ab92c
> [ 1.813312] RDX: 1ffff11017c8a600 RSI: ffffffff8fe3dec0 RDI:
> 0000000000000002
> [ 1.814701] RBP: ffffffff8fe07c90 R08: 0000000000000000 R09:
> fffffbfff212ebfd
> [ 1.816078] R10: ffffffff90975fe7 R11: fffffbfff212ebfc R12:
> 0000000000000800
> [ 1.817458] R13: 0000000000000800 R14: dffffc0000000000 R15:
> 0000000000000000
> [ 1.818841] FS: 0000000000000000(0000) GS:ffff88810a400000(0000)
> knlGS:0000000000000000
> [ 1.820406] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 1.821529] CR2: ffff8880be453000 CR3: 0000000024e30000 CR4:
> 00000000000006b0
> [ 1.822918] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> 0000000000000000
> [ 1.824299] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> 0000000000000400
> [ 1.825680] Kernel panic - not syncing: Fatal exception
> [ 1.827454] Dumping ftrace buffer:
> [ 1.828122] (ftrace buffer empty)
> [ 1.828821] Rebooting in 1 seconds..
>
> Thank you,
> George
>
> >
> > Failure is intermittent, so takes a lot of retries.
> >
> > Thank you,
> > George
> >
> >>
> >>
> >>> CC-ing Rafeal.
> >>>
> >>>
> >>> From c37da50fdfc62cd4f7b23562b55661478c90a17d Mon Sep 17 00:00:00 2001
> >>> From: Konrad Rzeszutek Wilk <[email protected]>
> >>> Date: Tue, 2 Feb 2021 17:28:28 +0000
> >>> Subject: [PATCH] ibft: Put ibft_addr back
> >>>
> >>> Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
> >>> ---
> >>> drivers/firmware/iscsi_ibft.c | 19 +++++++++++++------
> >>> 1 file changed, 13 insertions(+), 6 deletions(-)
> >>>
> >>> diff --git a/drivers/firmware/iscsi_ibft.c
> >>> b/drivers/firmware/iscsi_ibft.c
> >>> index 7127a04..2a1a033 100644
> >>> --- a/drivers/firmware/iscsi_ibft.c
> >>> +++ b/drivers/firmware/iscsi_ibft.c
> >>> @@ -811,6 +811,10 @@ static void ibft_cleanup(void)
> >>> ibft_unregister();
> >>> iscsi_boot_destroy_kset(boot_kset);
> >>> }
> >>> + if (ibft_addr) {
> >>> + acpi_put_table((struct acpi_table_header *)ibft_addr);
> >>> + ibft_addr = NULL;
> >>> + }
> >>> }
> >>>
> >>> static void __exit ibft_exit(void)
> >>> @@ -835,13 +839,15 @@ static void __init acpi_find_ibft_region(void)
> >>> {
> >>> int i;
> >>> struct acpi_table_header *table = NULL;
> >>> + acpi_status status;
> >>>
> >>> if (acpi_disabled)
> >>> return;
> >>>
> >>> for (i = 0; i < ARRAY_SIZE(ibft_signs) && !ibft_addr; i++) {
> >>> - acpi_get_table(ibft_signs[i].sign, 0, &table);
> >>> - ibft_addr = (struct acpi_table_ibft *)table;
> >>> + status = acpi_get_table(ibft_signs[i].sign, 0, &table);
> >>> + if (ACPI_SUCCESS(status))
> >>> + ibft_addr = (struct acpi_table_ibft *)table;
> >>> }
> >>> }
> >>> #else
> >>> @@ -870,12 +876,13 @@ static int __init ibft_init(void)
> >>>
> >>> rc = ibft_check_device();
> >>> if (rc)
> >>> - return rc;
> >>> + goto out_free;
> >>>
> >>> boot_kset = iscsi_boot_create_kset("ibft");
> >>> - if (!boot_kset)
> >>> - return -ENOMEM;
> >>> -
> >>> + if (!boot_kset) {
> >>> + rc = -ENOMEM;
> >>> + goto out_free;
> >>> + }
> >>> /* Scan the IBFT for data and register the
> >>> kobjects. */
> >>> rc = ibft_register_kobjects(ibft_addr);
> >>> if (rc)
> >>> --
> >>> 1.8.3.1
> >>>
> >
>

2021-02-12 15:40:40

by David Hildenbrand

Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

On 12.02.21 14:51, Dmitry Vyukov wrote:
> On Fri, Feb 12, 2021 at 2:31 PM George Kennedy
> <[email protected]> wrote:
>> On 2/10/2021 4:51 PM, George Kennedy wrote:
>>> On 2/3/2021 2:35 PM, Dmitry Vyukov wrote:
>>>> On Wed, Feb 3, 2021 at 8:29 PM Konrad Rzeszutek Wilk
>>>> <[email protected]> wrote:
>>>>> Hey Dmitry, Rafael, George, please see below..
>>>>>
>>>>> On Wed, Jan 27, 2021 at 10:10:07PM +0100, Dmitry Vyukov wrote:
>>>>>> On Wed, Jan 27, 2021 at 9:01 PM George Kennedy
>>>>>> <[email protected]> wrote:
>>>>>>> Hi Dmitry,
>>>>>>>
>>>>>>> On 1/27/2021 1:48 PM, Dmitry Vyukov wrote:
>>>>>>>
>>>>>>> On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
>>>>>>> <[email protected]> wrote:
>>>>>>>
>>>>>>> On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
>>>>>>>
>>>>>>> During boot of kernel with CONFIG_KASAN the following KASAN false
>>>>>>> positive failure will occur when ibft_init() reads the
>>>>>>> ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
>>>>>>>
>>>>>>> The ACPI iBFT table is not allocated, and the iscsi driver uses
>>>>>>> a pointer to it to calculate checksum, etc. KASAN complains
>>>>>>> about this pointer with use-after-free, which this is not.
>>>>>>>
>>>>>>> Andrey, Alexander, Dmitry,
>>>>>>>
>>>>>>> I think this is the right way for this, but was wondering if you have
>>>>>>> other suggestions?
>>>>>>>
>>>>>>> Thanks!
>>>>>>>
>>>>>>> Hi George, Konrad,
>>>>>>>
>>>>>>> Please provide a sample KASAN report and kernel version to match
>>>>>>> line numbers.
>>>>>>>
>>>>>>> 5.4.17-2102.200.0.0.20210106_0000
>>>>>>>
>>>>>>> [ 24.413536] iBFT detected.
>>>>>>> [ 24.414074]
>>>>>>> ==================================================================
>>>>>>> [ 24.407342] BUG: KASAN: use-after-free in ibft_init+0x134/0xb8b
>>>>>>> [ 24.407342] Read of size 4 at addr ffff8880be452004 by task
>>>>>>> swapper/0/1
>>>>>>> [ 24.407342]
>>>>>>> [ 24.407342] CPU: 1 PID: 1 Comm: swapper/0 Not tainted
>>>>>>> 5.4.17-2102.200.0.0.20210106_0000.syzk #1
>>>>>>> [ 24.407342] Hardware name: QEMU Standard PC (i440FX + PIIX,
>>>>>>> 1996), BIOS 0.0.0 02/06/2015
>>>>>>> [ 24.407342] Call Trace:
>>>>>>> [ 24.407342] dump_stack+0xd4/0x119
>>>>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>>>>> [ 24.407342] print_address_description.constprop.6+0x20/0x220
>>>>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>>>>> [ 24.407342] __kasan_report.cold.9+0x37/0x77
>>>>>>> [ 24.407342] ? ibft_init+0x134/0xb8b
>>>>>>> [ 24.407342] kasan_report+0x14/0x1b
>>>>>>> [ 24.407342] __asan_report_load_n_noabort+0xf/0x11
>>>>>>> [ 24.407342] ibft_init+0x134/0xb8b
>>>>>>> [ 24.407342] ? dmi_sysfs_init+0x1a5/0x1a5
>>>>>>> [ 24.407342] ? dmi_walk+0x72/0x89
>>>>>>> [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
>>>>>>> [ 24.407342] ? rvt_init_port+0x110/0x101
>>>>>>> [ 24.407342] ? ibft_check_initiator_for+0x159/0x159
>>>>>>> [ 24.407342] do_one_initcall+0xc3/0x44d
>>>>>>> [ 24.407342] ? perf_trace_initcall_level+0x410/0x405
>>>>>>> [ 24.407342] kernel_init_freeable+0x551/0x673
>>>>>>> [ 24.407342] ? start_kernel+0x94b/0x94b
>>>>>>> [ 24.407342] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
>>>>>>> [ 24.407342] ? __kasan_check_write+0x14/0x16
>>>>>>> [ 24.407342] ? rest_init+0xe6/0xe6
>>>>>>> [ 24.407342] kernel_init+0x16/0x1bd
>>>>>>> [ 24.407342] ? rest_init+0xe6/0xe6
>>>>>>> [ 24.407342] ret_from_fork+0x2b/0x36
>>>>>>> [ 24.407342]
>>>>>>> [ 24.407342] The buggy address belongs to the page:
>>>>>>> [ 24.407342] page:ffffea0002f91480 refcount:0 mapcount:0
>>>>>>> mapping:0000000000000000 index:0x1
>>>>>>> [ 24.407342] flags: 0xfffffc0000000()
>>>>>>> [ 24.407342] raw: 000fffffc0000000 ffffea0002fca588
>>>>>>> ffffea0002fb1a88 0000000000000000
>>>>>>> [ 24.407342] raw: 0000000000000001 0000000000000000
>>>>>>> 00000000ffffffff 0000000000000000
>>>>>>> [ 24.407342] page dumped because: kasan: bad access detected
>>>>>>> [ 24.407342]
>>>>>>> [ 24.407342] Memory state around the buggy address:
>>>>>>> [ 24.407342] ffff8880be451f00: ff ff ff ff ff ff ff ff ff ff ff
>>>>>>> ff ff ff ff ff
>>>>>>> [ 24.407342] ffff8880be451f80: ff ff ff ff ff ff ff ff ff ff ff
>>>>>>> ff ff ff ff ff
>>>>>>> [ 24.407342] >ffff8880be452000: ff ff ff ff ff ff ff ff ff ff ff
>>>>>>> ff ff ff ff ff
>>>>>>> [ 24.407342] ^
>>>>>>> [ 24.407342] ffff8880be452080: ff ff ff ff ff ff ff ff ff ff ff
>>>>>>> ff ff ff ff ff
>>>>>>> [ 24.407342] ffff8880be452100: ff ff ff ff ff ff ff ff ff ff ff
>>>>>>> ff ff ff ff ff
>>>>>>> [ 24.407342]
>>>>>>> ==================================================================
>>>>>>> [ 24.407342] Disabling lock debugging due to kernel taint
>>>>>>> [ 24.451021] Kernel panic - not syncing: panic_on_warn set ...
>>>>>>> [ 24.452002] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G B
>>>>>>> 5.4.17-2102.200.0.0.20210106_0000.syzk #1
>>>>>>> [ 24.452002] Hardware name: QEMU Standard PC (i440FX + PIIX,
>>>>>>> 1996), BIOS 0.0.0 02/06/2015
>>>>>>> [ 24.452002] Call Trace:
>>>>>>> [ 24.452002] dump_stack+0xd4/0x119
>>>>>>> [ 24.452002] ? ibft_init+0x102/0xb8b
>>>>>>> [ 24.452002] panic+0x28f/0x6e0
>>>>>>> [ 24.452002] ? __warn_printk+0xe0/0xe0
>>>>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>>>>> [ 24.452002] ? add_taint+0x68/0xb3
>>>>>>> [ 24.452002] ? add_taint+0x68/0xb3
>>>>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>>>>> [ 24.452002] end_report+0x4c/0x54
>>>>>>> [ 24.452002] __kasan_report.cold.9+0x55/0x77
>>>>>>> [ 24.452002] ? ibft_init+0x134/0xb8b
>>>>>>> [ 24.452002] kasan_report+0x14/0x1b
>>>>>>> [ 24.452002] __asan_report_load_n_noabort+0xf/0x11
>>>>>>> [ 24.452002] ibft_init+0x134/0xb8b
>>>>>>> [ 24.452002] ? dmi_sysfs_init+0x1a5/0x1a5
>>>>>>> [ 24.452002] ? dmi_walk+0x72/0x89
>>>>>>> [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
>>>>>>> [ 24.452002] ? rvt_init_port+0x110/0x101
>>>>>>> [ 24.452002] ? ibft_check_initiator_for+0x159/0x159
>>>>>>> [ 24.452002] do_one_initcall+0xc3/0x44d
>>>>>>> [ 24.452002] ? perf_trace_initcall_level+0x410/0x405
>>>>>>> [ 24.452002] kernel_init_freeable+0x551/0x673
>>>>>>> [ 24.452002] ? start_kernel+0x94b/0x94b
>>>>>>> [ 24.452002] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
>>>>>>> [ 24.452002] ? __kasan_check_write+0x14/0x16
>>>>>>> [ 24.452002] ? rest_init+0xe6/0xe6
>>>>>>> [ 24.452002] kernel_init+0x16/0x1bd
>>>>>>> [ 24.452002] ? rest_init+0xe6/0xe6
>>>>>>> [ 24.452002] ret_from_fork+0x2b/0x36
>>>>>>> [ 24.452002] Dumping ftrace buffer:
>>>>>>> [ 24.452002] ---------------------------------
>>>>>>> [ 24.452002] swapper/-1 1.... 24564337us : rdmaip_init:
>>>>>>> 2924: rdmaip_init: Active Bonding is DISABLED
>>>>>>> [ 24.452002] ---------------------------------
>>>>>>> [ 24.452002] Kernel Offset: disabled
>>>>>>> [ 24.452002] Rebooting in 1 seconds..
>>>>>>>
>>>>>>> Why does KASAN think the address is freed? For that to happen that
>>>>>>> memory should have been freed. I don't remember any similar false
>>>>>>> positives from KASAN, so this looks a bit suspicious.
>>>>>>>
>>>>>>> I'm not sure why KASAN thinks the address is freed. There are
>>>>>>> other modules where KASAN/KCOV is disabled on boot.
>>>>>>> Could this be for a similar reason?
>>>>>> Most of these files are disabled because they cause recursion in
>>>>>> instrumentation, or execute too early in bootstrap process (before
>>>>>> kasan_init).
>>>>>>
>>>>>> Somehow the table pointer in ibft_init points to a freed page. I
>>>>>> tracked it down to here:
>>>>>> https://elixir.bootlin.com/linux/v5.4.17/source/drivers/acpi/acpica/tbutils.c#L399
>>>>>>
>>>>>> but I can't find where this table_desc->pointer comes from. Perhaps it
>>>>> It is what the BIOS generated. It usually points to some memory
>>>>> location in right under 4GB and the BIOS stashes the DSDT, iBFT, and
>>>>> other tables in there.
>>>>>
>>>>>> uses some allocation method that's not supported by KASAN? However,
>>>>>> it's the only such case that I've seen, so it's a bit weird. Could it
>>>>>> use something like memblock_alloc? Or maybe that page was in fact
>>>>>> freed?... Too bad KASAN does not print free stack for pages, maybe
>>>>>> it's not too hard to do if CONFIG_PAGE_OWNER is enabled...
>>>>> Hm, there is a comment in the acpi_get_table speaking about the
>>>>> requirement of having a acpi_put_table and:
>>>>>
>>>>>
>>>>> * DESCRIPTION: Finds and verifies an ACPI table. Table must be in the
>>>>> * RSDT/XSDT.
>>>>> * Note that an early stage acpi_get_table() call must
>>>>> be paired
>>>>> * with an early stage acpi_put_table() call.
>>>>> otherwise the table
>>>>> * pointer mapped by the early stage mapping
>>>>> implementation may be
>>>>> * erroneously unmapped by the late stage unmapping
>>>>> implementation
>>>>> * in an acpi_put_table() invoked during the late stage.
>>>>> *
>>>>>
>>>>> Which would imply that I should use acpi_put_table in the error path
>>>>> (see below a patch), but also copy the structure instead of depending
>>>>> on ACPI keeping it mapped for me. I think.
>>>> Hi Konrad,
>>>>
>>>> Thanks for looking into this.
>>>> If ACPI unmaps this page, that would perfectly explain the KASAN report.
>>>>
>>>> George, does this patch eliminate the KASAN report for you?
>>>
>>> Hi Dmitry,
>>>
>>> No luck with the patch. Tried high level bisect instead. Here are the
>>> results:
>>>
>>> BUG: KASAN: use-after-free in ibft_init+0x134/0xc49
>>>
>>> Bisect status:
>>> v5.11-rc6 Sun Jan 31 13:50:09 2021 -0800 Failed
>>> v5.11-rc1 Sun Dec 27 15:30:22 2020 -0800 Failed
>>> v5.10 Sun Dec 13 14:41:30 2020 -0800 Failed
>>> v5.10-rc6 Sun Nov 29 15:50:50 2020 -0800 Failed
>>> v5.10-rc5 Sun Nov 22 15:36:08 2020 -0800 Failed
>>> v5.10-rc4 Sun Nov 15 16:44:31 2020 -0800 Failed
>>> v5.10-rc3 Sun Nov 8 16:10:16 2020 -0800 Failed
>>> v5.10-rc2 Sun Nov 1 14:43:52 2020 -0800 Failed
>>> v5.10-rc1 Sun Oct 25 15:14:11 2020 -0700 Failed
>>> v5.9 Sun Oct 11 14:15:50 2020 -0700 OK - 10 reboots so
>>> far w/o kasan failure
>>>
>>> So, will look at what changed between v5.9 and v5.10-rc1
>>
>> git bisect has identified the following as the offending commit:
>>
>> 2020-10-16 [email protected] - 7fef431 2020-10-15 David
>> Hildenbrand mm/page_alloc: place pages to tail in __free_pages_core()
>
> I think this suggests that this is a real use-after-free and the
> page_alloc change just exposed a latent bug.

That commit is ridiculously good at finding latent BUGs. Memory gets
allocated and used in the reverse order. So could be that this is
exposing yet another latent bug.

For example:
https://lkml.kernel.org/r/[email protected]

Or a longer discussion at:
https://lkml.kernel.org/r/[email protected]


Anyhow, let me know in case it looks like this time it's actually my
commit that broke something (although somewhat unlikely I have to say).

--
Thanks,

David / dhildenb

2021-02-12 18:08:33

by George Kennedy

Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

On 2/12/2021 10:36 AM, David Hildenbrand wrote:
> On 12.02.21 14:51, Dmitry Vyukov wrote:
>> On Fri, Feb 12, 2021 at 2:31 PM George Kennedy
>> <[email protected]> wrote:
>>> On 2/10/2021 4:51 PM, George Kennedy wrote:
>>>> On 2/3/2021 2:35 PM, Dmitry Vyukov wrote:
>>>>> On Wed, Feb 3, 2021 at 8:29 PM Konrad Rzeszutek Wilk
>>>>> <[email protected]> wrote:
>>>>>> Hey Dmitry, Rafael, George, please see below..
>>>>>>
>>>>>> On Wed, Jan 27, 2021 at 10:10:07PM +0100, Dmitry Vyukov wrote:
>>>>>>> On Wed, Jan 27, 2021 at 9:01 PM George Kennedy
>>>>>>> <[email protected]> wrote:
>>>>>>>> Hi Dmitry,
>>>>>>>>
>>>>>>>> On 1/27/2021 1:48 PM, Dmitry Vyukov wrote:
>>>>>>>>
>>>>>>>> On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
>>>>>>>> <[email protected]> wrote:
>>>>>>>>
>>>>>>>> On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
>>>>>>>>
>>>>>>>> During boot of kernel with CONFIG_KASAN the following KASAN false
>>>>>>>> positive failure will occur when ibft_init() reads the
>>>>>>>> ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
>>>>>>>>
>>>>>>>> The ACPI iBFT table is not allocated, and the iscsi driver uses
>>>>>>>> a pointer to it to calculate checksum, etc. KASAN complains
>>>>>>>> about this pointer with use-after-free, which this is not.
>>>>>>>>
>>>>>>>> Andrey, Alexander, Dmitry,
>>>>>>>>
>>>>>>>> I think this is the right way for this, but was wondering if
>>>>>>>> you have
>>>>>>>> other suggestions?
>>>>>>>>
>>>>>>>> Thanks!
>>>>>>>>
>>>>>>>> Hi George, Konrad,
>>>>>>>>
>>>>>>>> Please provide a sample KASAN report and kernel version to match
>>>>>>>> line numbers.
>>>>>>>>
>>>>>>>> 5.4.17-2102.200.0.0.20210106_0000
>>>>>>>>
>>>>>>>> [   24.413536] iBFT detected.
>>>>>>>> [   24.414074]
>>>>>>>> ==================================================================
>>>>>>>> [   24.407342] BUG: KASAN: use-after-free in ibft_init+0x134/0xb8b
>>>>>>>> [   24.407342] Read of size 4 at addr ffff8880be452004 by task
>>>>>>>> swapper/0/1
>>>>>>>> [   24.407342]
>>>>>>>> [   24.407342] CPU: 1 PID: 1 Comm: swapper/0 Not tainted
>>>>>>>> 5.4.17-2102.200.0.0.20210106_0000.syzk #1
>>>>>>>> [   24.407342] Hardware name: QEMU Standard PC (i440FX + PIIX,
>>>>>>>> 1996), BIOS 0.0.0 02/06/2015
>>>>>>>> [   24.407342] Call Trace:
>>>>>>>> [   24.407342]  dump_stack+0xd4/0x119
>>>>>>>> [   24.407342]  ? ibft_init+0x134/0xb8b
>>>>>>>> [   24.407342] print_address_description.constprop.6+0x20/0x220
>>>>>>>> [   24.407342]  ? ibft_init+0x134/0xb8b
>>>>>>>> [   24.407342]  ? ibft_init+0x134/0xb8b
>>>>>>>> [   24.407342]  __kasan_report.cold.9+0x37/0x77
>>>>>>>> [   24.407342]  ? ibft_init+0x134/0xb8b
>>>>>>>> [   24.407342]  kasan_report+0x14/0x1b
>>>>>>>> [   24.407342] __asan_report_load_n_noabort+0xf/0x11
>>>>>>>> [   24.407342]  ibft_init+0x134/0xb8b
>>>>>>>> [   24.407342]  ? dmi_sysfs_init+0x1a5/0x1a5
>>>>>>>> [   24.407342]  ? dmi_walk+0x72/0x89
>>>>>>>> [   24.407342]  ? ibft_check_initiator_for+0x159/0x159
>>>>>>>> [   24.407342]  ? rvt_init_port+0x110/0x101
>>>>>>>> [   24.407342]  ? ibft_check_initiator_for+0x159/0x159
>>>>>>>> [   24.407342]  do_one_initcall+0xc3/0x44d
>>>>>>>> [   24.407342]  ? perf_trace_initcall_level+0x410/0x405
>>>>>>>> [   24.407342]  kernel_init_freeable+0x551/0x673
>>>>>>>> [   24.407342]  ? start_kernel+0x94b/0x94b
>>>>>>>> [   24.407342]  ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
>>>>>>>> [   24.407342]  ? __kasan_check_write+0x14/0x16
>>>>>>>> [   24.407342]  ? rest_init+0xe6/0xe6
>>>>>>>> [   24.407342]  kernel_init+0x16/0x1bd
>>>>>>>> [   24.407342]  ? rest_init+0xe6/0xe6
>>>>>>>> [   24.407342]  ret_from_fork+0x2b/0x36
>>>>>>>> [   24.407342]
>>>>>>>> [   24.407342] The buggy address belongs to the page:
>>>>>>>> [   24.407342] page:ffffea0002f91480 refcount:0 mapcount:0
>>>>>>>> mapping:0000000000000000 index:0x1
>>>>>>>> [   24.407342] flags: 0xfffffc0000000()
>>>>>>>> [   24.407342] raw: 000fffffc0000000 ffffea0002fca588
>>>>>>>> ffffea0002fb1a88 0000000000000000
>>>>>>>> [   24.407342] raw: 0000000000000001 0000000000000000
>>>>>>>> 00000000ffffffff 0000000000000000
>>>>>>>> [   24.407342] page dumped because: kasan: bad access detected
>>>>>>>> [   24.407342]
>>>>>>>> [   24.407342] Memory state around the buggy address:
>>>>>>>> [   24.407342]  ffff8880be451f00: ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>> ff ff ff ff ff
>>>>>>>> [   24.407342]  ffff8880be451f80: ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>> ff ff ff ff ff
>>>>>>>> [   24.407342] >ffff8880be452000: ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>> ff ff ff ff ff
>>>>>>>> [   24.407342]                    ^
>>>>>>>> [   24.407342]  ffff8880be452080: ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>> ff ff ff ff ff
>>>>>>>> [   24.407342]  ffff8880be452100: ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>> ff ff ff ff ff
>>>>>>>> [   24.407342]
>>>>>>>> ==================================================================
>>>>>>>> [   24.407342] Disabling lock debugging due to kernel taint
>>>>>>>> [   24.451021] Kernel panic - not syncing: panic_on_warn set ...
>>>>>>>> [   24.452002] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G B
>>>>>>>> 5.4.17-2102.200.0.0.20210106_0000.syzk #1
>>>>>>>> [   24.452002] Hardware name: QEMU Standard PC (i440FX + PIIX,
>>>>>>>> 1996), BIOS 0.0.0 02/06/2015
>>>>>>>> [   24.452002] Call Trace:
>>>>>>>> [   24.452002]  dump_stack+0xd4/0x119
>>>>>>>> [   24.452002]  ? ibft_init+0x102/0xb8b
>>>>>>>> [   24.452002]  panic+0x28f/0x6e0
>>>>>>>> [   24.452002]  ? __warn_printk+0xe0/0xe0
>>>>>>>> [   24.452002]  ? ibft_init+0x134/0xb8b
>>>>>>>> [   24.452002]  ? add_taint+0x68/0xb3
>>>>>>>> [   24.452002]  ? add_taint+0x68/0xb3
>>>>>>>> [   24.452002]  ? ibft_init+0x134/0xb8b
>>>>>>>> [   24.452002]  ? ibft_init+0x134/0xb8b
>>>>>>>> [   24.452002]  end_report+0x4c/0x54
>>>>>>>> [   24.452002]  __kasan_report.cold.9+0x55/0x77
>>>>>>>> [   24.452002]  ? ibft_init+0x134/0xb8b
>>>>>>>> [   24.452002]  kasan_report+0x14/0x1b
>>>>>>>> [   24.452002] __asan_report_load_n_noabort+0xf/0x11
>>>>>>>> [   24.452002]  ibft_init+0x134/0xb8b
>>>>>>>> [   24.452002]  ? dmi_sysfs_init+0x1a5/0x1a5
>>>>>>>> [   24.452002]  ? dmi_walk+0x72/0x89
>>>>>>>> [   24.452002]  ? ibft_check_initiator_for+0x159/0x159
>>>>>>>> [   24.452002]  ? rvt_init_port+0x110/0x101
>>>>>>>> [   24.452002]  ? ibft_check_initiator_for+0x159/0x159
>>>>>>>> [   24.452002]  do_one_initcall+0xc3/0x44d
>>>>>>>> [   24.452002]  ? perf_trace_initcall_level+0x410/0x405
>>>>>>>> [   24.452002]  kernel_init_freeable+0x551/0x673
>>>>>>>> [   24.452002]  ? start_kernel+0x94b/0x94b
>>>>>>>> [   24.452002]  ? __sanitizer_cov_trace_const_cmp1+0x1a/0x1c
>>>>>>>> [   24.452002]  ? __kasan_check_write+0x14/0x16
>>>>>>>> [   24.452002]  ? rest_init+0xe6/0xe6
>>>>>>>> [   24.452002]  kernel_init+0x16/0x1bd
>>>>>>>> [   24.452002]  ? rest_init+0xe6/0xe6
>>>>>>>> [   24.452002]  ret_from_fork+0x2b/0x36
>>>>>>>> [   24.452002] Dumping ftrace buffer:
>>>>>>>> [   24.452002] ---------------------------------
>>>>>>>> [   24.452002] swapper/-1         1.... 24564337us : rdmaip_init:
>>>>>>>> 2924: rdmaip_init: Active Bonding is DISABLED
>>>>>>>> [   24.452002] ---------------------------------
>>>>>>>> [   24.452002] Kernel Offset: disabled
>>>>>>>> [   24.452002] Rebooting in 1 seconds..
>>>>>>>>
>>>>>>>> Why does KASAN think the address is freed? For that to happen that
>>>>>>>> memory should have been freed. I don't remember any similar false
>>>>>>>> positives from KASAN, so this looks a bit suspicious.
>>>>>>>>
>>>>>>>> I'm not sure why KASAN thinks the address is freed. There are
>>>>>>>> other modules where KASAN/KCOV is disabled on boot.
>>>>>>>> Could this be for a similar reason?
>>>>>>> Most of these files are disabled because they cause recursion in
>>>>>>> instrumentation, or execute too early in bootstrap process (before
>>>>>>> kasan_init).
>>>>>>>
>>>>>>> Somehow the table pointer in ibft_init points to a freed page. I
>>>>>>> tracked it down to here:
>>>>>>> https://elixir.bootlin.com/linux/v5.4.17/source/drivers/acpi/acpica/tbutils.c#L399
>>>>>>>
>>>>>>>
>>>>>>> but I can't find where this table_desc->pointer comes from.
>>>>>>> Perhaps it
>>>>>> It is what the BIOS generated. It usually points to some memory
>>>>>> location in right under 4GB and the BIOS stashes the DSDT, iBFT, and
>>>>>> other tables in there.
>>>>>>
>>>>>>> uses some allocation method that's not supported by KASAN? However,
>>>>>>> it's the only such case that I've seen, so it's a bit weird.
>>>>>>> Could it
>>>>>>> use something like memblock_alloc? Or maybe that page was in fact
>>>>>>> freed?... Too bad KASAN does not print free stack for pages, maybe
>>>>>>> it's not too hard to do if CONFIG_PAGE_OWNER is enabled...
>>>>>> Hm, there is a comment in the acpi_get_table speaking about the
>>>>>> requirement of having a acpi_put_table and:
>>>>>>
>>>>>>
>>>>>>    * DESCRIPTION: Finds and verifies an ACPI table. Table must be
>>>>>> in the
>>>>>>    *              RSDT/XSDT.
>>>>>>    *              Note that an early stage acpi_get_table() call
>>>>>> must
>>>>>> be paired
>>>>>>    *              with an early stage acpi_put_table() call.
>>>>>> otherwise the table
>>>>>>    *              pointer mapped by the early stage mapping
>>>>>> implementation may be
>>>>>>    *              erroneously unmapped by the late stage unmapping
>>>>>> implementation
>>>>>>    *              in an acpi_put_table() invoked during the late
>>>>>> stage.
>>>>>>    *
>>>>>>
>>>>>> Which would imply that I should use acpi_put_table in the error path
>>>>>> (see below a patch), but also copy the structure instead of
>>>>>> depending
>>>>>> on ACPI keeping it mapped for me. I think.
>>>>> Hi Konrad,
>>>>>
>>>>> Thanks for looking into this.
>>>>> If ACPI unmaps this page, that would perfectly explain the KASAN
>>>>> report.
>>>>>
>>>>> George, does this patch eliminate the KASAN report for you?
>>>>
>>>> Hi Dmitry,
>>>>
>>>> No luck with the patch. Tried high level bisect instead. Here are the
>>>> results:
>>>>
>>>> BUG: KASAN: use-after-free in ibft_init+0x134/0xc49
>>>>
>>>> Bisect status:
>>>> v5.11-rc6 Sun Jan 31 13:50:09 2021 -0800     Failed
>>>> v5.11-rc1 Sun Dec 27 15:30:22 2020 -0800    Failed
>>>> v5.10 Sun Dec 13 14:41:30 2020 -0800           Failed
>>>> v5.10-rc6 Sun Nov 29 15:50:50 2020 -0800    Failed
>>>> v5.10-rc5 Sun Nov 22 15:36:08 2020 -0800    Failed
>>>> v5.10-rc4 Sun Nov 15 16:44:31 2020 -0800    Failed
>>>> v5.10-rc3 Sun Nov 8 16:10:16 2020 -0800      Failed
>>>> v5.10-rc2 Sun Nov 1 14:43:52 2020 -0800      Failed
>>>> v5.10-rc1 Sun Oct 25 15:14:11 2020 -0700     Failed
>>>> v5.9 Sun Oct 11 14:15:50 2020 -0700              OK - 10 reboots so
>>>> far w/o kasan failure
>>>>
>>>> So, will look at what changed between v5.9 and v5.10-rc1
>>>
>>> git bisect has identified the following as the offending commit:
>>>
>>> 2020-10-16 [email protected] - 7fef431 2020-10-15 David
>>> Hildenbrand mm/page_alloc: place pages to tail in __free_pages_core()
>>
>> I think this suggests that this is a real use-after-free and the
>> page_alloc change just exposed a latent bug.
>
> That commit is ridiculously good at finding latent BUGs. Memory gets
> allocated and used in the reverse order. So could be that this is
> exposing yet another latent bug.
>
> For example:
> https://lkml.kernel.org/r/[email protected]
>
> Or a longer discussion at:
> https://lkml.kernel.org/r/[email protected]
>
>
> Anyhow, let me know in case it looks like this time it's actually my
> commit that broke something (although somewhat unlikely I have to say).

Thank you Dmitry & David,

Good read and agree - great smoke test for latent bugs.

Continuing to search for the real bug.

George