2019-09-11 07:54:46

by Igor Mammedov

[permalink] [raw]
Subject: [PATCH v2] KVM: s390: kvm_s390_vm_start_migration: check dirty_bitmap before using it as target for memset()

If userspace doesn't set KVM_MEM_LOG_DIRTY_PAGES on memslot before calling
kvm_s390_vm_start_migration(), kernel will oops with:

Unable to handle kernel pointer dereference in virtual kernel address space
Failing address: 0000000000000000 TEID: 0000000000000483
Fault in home space mode while using kernel ASCE.
AS:0000000002a2000b R2:00000001bff8c00b R3:00000001bff88007 S:00000001bff91000 P:000000000000003d
Oops: 0004 ilc:2 [#1] SMP
...
Call Trace:
([<001fffff804ec552>] kvm_s390_vm_set_attr+0x347a/0x3828 [kvm])
[<001fffff804ecfc0>] kvm_arch_vm_ioctl+0x6c0/0x1998 [kvm]
[<001fffff804b67e4>] kvm_vm_ioctl+0x51c/0x11a8 [kvm]
[<00000000008ba572>] do_vfs_ioctl+0x1d2/0xe58
[<00000000008bb284>] ksys_ioctl+0x8c/0xb8
[<00000000008bb2e2>] sys_ioctl+0x32/0x40
[<000000000175552c>] system_call+0x2b8/0x2d8
INFO: lockdep is turned off.
Last Breaking-Event-Address:
[<0000000000dbaf60>] __memset+0xc/0xa0

due to ms->dirty_bitmap being NULL, which might crash the host.

Make sure that ms->dirty_bitmap is set before using it or
return -ENIVAL otherwise.

Fixes: afdad61615cc ("KVM: s390: Fix storage attributes migration with memory slots")
Signed-off-by: Igor Mammedov <[email protected]>
---
Cc: [email protected] # v4.19+

v2:
- remove not true anym 'warning' clause in commit message
v2:
- drop WARN()

arch/s390/kvm/kvm-s390.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index f329dcb3f44c..2a40cd3e40b4 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1018,6 +1018,8 @@ static int kvm_s390_vm_start_migration(struct kvm *kvm)
/* mark all the pages in active slots as dirty */
for (slotnr = 0; slotnr < slots->used_slots; slotnr++) {
ms = slots->memslots + slotnr;
+ if (!ms->dirty_bitmap)
+ return -EINVAL;
/*
* The second half of the bitmap is only used on x86,
* and would be wasted otherwise, so we put it to good
--
2.18.1


2019-09-11 08:02:07

by David Hildenbrand

[permalink] [raw]
Subject: Re: [PATCH v2] KVM: s390: kvm_s390_vm_start_migration: check dirty_bitmap before using it as target for memset()

On 11.09.19 09:52, Igor Mammedov wrote:
> If userspace doesn't set KVM_MEM_LOG_DIRTY_PAGES on memslot before calling
> kvm_s390_vm_start_migration(), kernel will oops with:
>
> Unable to handle kernel pointer dereference in virtual kernel address space
> Failing address: 0000000000000000 TEID: 0000000000000483
> Fault in home space mode while using kernel ASCE.
> AS:0000000002a2000b R2:00000001bff8c00b R3:00000001bff88007 S:00000001bff91000 P:000000000000003d
> Oops: 0004 ilc:2 [#1] SMP
> ...
> Call Trace:
> ([<001fffff804ec552>] kvm_s390_vm_set_attr+0x347a/0x3828 [kvm])
> [<001fffff804ecfc0>] kvm_arch_vm_ioctl+0x6c0/0x1998 [kvm]
> [<001fffff804b67e4>] kvm_vm_ioctl+0x51c/0x11a8 [kvm]
> [<00000000008ba572>] do_vfs_ioctl+0x1d2/0xe58
> [<00000000008bb284>] ksys_ioctl+0x8c/0xb8
> [<00000000008bb2e2>] sys_ioctl+0x32/0x40
> [<000000000175552c>] system_call+0x2b8/0x2d8
> INFO: lockdep is turned off.
> Last Breaking-Event-Address:
> [<0000000000dbaf60>] __memset+0xc/0xa0
>
> due to ms->dirty_bitmap being NULL, which might crash the host.
>
> Make sure that ms->dirty_bitmap is set before using it or
> return -ENIVAL otherwise.

s/ENIVAL/EINVAL/

I assume Christian can fix that up when applying.

>
> Fixes: afdad61615cc ("KVM: s390: Fix storage attributes migration with memory slots")
> Signed-off-by: Igor Mammedov <[email protected]>
> ---
> Cc: [email protected] # v4.19+
>
> v2:
> - remove not true anym 'warning' clause in commit message
> v2:
> - drop WARN()
>
> arch/s390/kvm/kvm-s390.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index f329dcb3f44c..2a40cd3e40b4 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -1018,6 +1018,8 @@ static int kvm_s390_vm_start_migration(struct kvm *kvm)
> /* mark all the pages in active slots as dirty */
> for (slotnr = 0; slotnr < slots->used_slots; slotnr++) {
> ms = slots->memslots + slotnr;
> + if (!ms->dirty_bitmap)
> + return -EINVAL;
> /*
> * The second half of the bitmap is only used on x86,
> * and would be wasted otherwise, so we put it to good
>

You should keep the RB's, especially when only rephrasing the commit
message ;)

Reviewed-by: David Hildenbrand <[email protected]>

--

Thanks,

David / dhildenb

2019-09-11 08:39:10

by Janosch Frank

[permalink] [raw]
Subject: Re: [PATCH v2] KVM: s390: kvm_s390_vm_start_migration: check dirty_bitmap before using it as target for memset()

On 9/11/19 9:52 AM, Igor Mammedov wrote:
> If userspace doesn't set KVM_MEM_LOG_DIRTY_PAGES on memslot before calling
> kvm_s390_vm_start_migration(), kernel will oops with:
>
> Unable to handle kernel pointer dereference in virtual kernel address space
> Failing address: 0000000000000000 TEID: 0000000000000483
> Fault in home space mode while using kernel ASCE.
> AS:0000000002a2000b R2:00000001bff8c00b R3:00000001bff88007 S:00000001bff91000 P:000000000000003d
> Oops: 0004 ilc:2 [#1] SMP
> ...
> Call Trace:
> ([<001fffff804ec552>] kvm_s390_vm_set_attr+0x347a/0x3828 [kvm])
> [<001fffff804ecfc0>] kvm_arch_vm_ioctl+0x6c0/0x1998 [kvm]
> [<001fffff804b67e4>] kvm_vm_ioctl+0x51c/0x11a8 [kvm]
> [<00000000008ba572>] do_vfs_ioctl+0x1d2/0xe58
> [<00000000008bb284>] ksys_ioctl+0x8c/0xb8
> [<00000000008bb2e2>] sys_ioctl+0x32/0x40
> [<000000000175552c>] system_call+0x2b8/0x2d8
> INFO: lockdep is turned off.
> Last Breaking-Event-Address:
> [<0000000000dbaf60>] __memset+0xc/0xa0
>
> due to ms->dirty_bitmap being NULL, which might crash the host.
>
> Make sure that ms->dirty_bitmap is set before using it or
> return -ENIVAL otherwise.

Fixed that while picking and added my reviewed-by, as well as the others
you removed.
Thanks for your patch.


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