syzbot reported a warning from Ion:
WARNING: CPU: 1 PID: 3485 at mm/page_alloc.c:3926
...
__alloc_pages_nodemask+0x9fb/0xd80 mm/page_alloc.c:4252
alloc_pages_current+0xb6/0x1e0 mm/mempolicy.c:2036
alloc_pages include/linux/gfp.h:492 [inline]
ion_system_contig_heap_allocate+0x40/0x2c0
drivers/staging/android/ion/ion_system_heap.c:374
ion_buffer_create drivers/staging/android/ion/ion.c:93 [inline]
ion_alloc+0x2c1/0x9e0 drivers/staging/android/ion/ion.c:420
ion_ioctl+0x26d/0x380 drivers/staging/android/ion/ion-ioctl.c:84
vfs_ioctl fs/ioctl.c:46 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
This is a warning about attempting to allocate order > MAX_ORDER. This
is coming from a userspace Ion allocation request. Since userspace is
free to request however much memory it wants (and the kernel is free to
deny its allocation), silence the allocation attempt with __GFP_NOWARN
in case it fails.
Reported-by: [email protected]
Reported-by: syzbot <[email protected]>
Signed-off-by: Laura Abbott <[email protected]>
---
drivers/staging/android/ion/ion_system_heap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
index 71c4228f8238..bc19cdd30637 100644
--- a/drivers/staging/android/ion/ion_system_heap.c
+++ b/drivers/staging/android/ion/ion_system_heap.c
@@ -362,7 +362,7 @@ static int ion_system_contig_heap_allocate(struct ion_heap *heap,
unsigned long i;
int ret;
- page = alloc_pages(low_order_gfp_flags, order);
+ page = alloc_pages(low_order_gfp_flags | __GFP_NOWARN, order);
if (!page)
return -ENOMEM;
--
2.14.3
Syzbot reported a warning with Ion:
WARNING: CPU: 0 PID: 3502 at drivers/staging/android/ion/ion-ioctl.c:73 ion_ioctl+0x2db/0x380 drivers/staging/android/ion/ion-ioctl.c:73
Kernel panic - not syncing: panic_on_warn set ...
This is a warning that validation of the ioctl fields failed. This was
deliberately added as a warning to make it very obvious to developers that
something needed to be fixed. In reality, this is overkill and disturbs
fuzzing. Switch to pr_warn for a message instead.
Reported-by: [email protected]
Reported-by: syzbot <[email protected]>
Signed-off-by: Laura Abbott <[email protected]>
---
drivers/staging/android/ion/ion-ioctl.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/staging/android/ion/ion-ioctl.c b/drivers/staging/android/ion/ion-ioctl.c
index 6ed2cc15c8c0..a8d3cc412fb9 100644
--- a/drivers/staging/android/ion/ion-ioctl.c
+++ b/drivers/staging/android/ion/ion-ioctl.c
@@ -60,8 +60,10 @@ long ion_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
return -EFAULT;
ret = validate_ioctl_arg(cmd, &data);
- if (WARN_ON_ONCE(ret))
+ if (ret) {
+ pr_warn_once("%s: ioctl validate failed\n", __func__);
return ret;
+ }
if (!(dir & _IOC_WRITE))
memset(&data, 0, sizeof(data));
--
2.14.3
Quoting Laura Abbott (2018-01-05 19:14:08)
> syzbot reported a warning from Ion:
>
> WARNING: CPU: 1 PID: 3485 at mm/page_alloc.c:3926
>
> ...
> __alloc_pages_nodemask+0x9fb/0xd80 mm/page_alloc.c:4252
> alloc_pages_current+0xb6/0x1e0 mm/mempolicy.c:2036
> alloc_pages include/linux/gfp.h:492 [inline]
> ion_system_contig_heap_allocate+0x40/0x2c0
> drivers/staging/android/ion/ion_system_heap.c:374
> ion_buffer_create drivers/staging/android/ion/ion.c:93 [inline]
> ion_alloc+0x2c1/0x9e0 drivers/staging/android/ion/ion.c:420
> ion_ioctl+0x26d/0x380 drivers/staging/android/ion/ion-ioctl.c:84
> vfs_ioctl fs/ioctl.c:46 [inline]
> do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
> SYSC_ioctl fs/ioctl.c:701 [inline]
> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>
> This is a warning about attempting to allocate order > MAX_ORDER. This
> is coming from a userspace Ion allocation request. Since userspace is
> free to request however much memory it wants (and the kernel is free to
> deny its allocation), silence the allocation attempt with __GFP_NOWARN
> in case it fails.
>
> Reported-by: [email protected]
> Reported-by: syzbot <[email protected]>
> Signed-off-by: Laura Abbott <[email protected]>
> ---
> drivers/staging/android/ion/ion_system_heap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
> index 71c4228f8238..bc19cdd30637 100644
> --- a/drivers/staging/android/ion/ion_system_heap.c
> +++ b/drivers/staging/android/ion/ion_system_heap.c
> @@ -362,7 +362,7 @@ static int ion_system_contig_heap_allocate(struct ion_heap *heap,
> unsigned long i;
> int ret;
>
> - page = alloc_pages(low_order_gfp_flags, order);
> + page = alloc_pages(low_order_gfp_flags | __GFP_NOWARN, order);
There's both high_order_gfp and low_order_gfp. The former includes
NOWARN and NORETRY.
Interesting, ion_system_heap_create_pools() tries to mix low_order and
high_order, but it only ever uses high_order flags. (orders[0] == 8
forcing a permanent switch from low_order_gfp to high_order_gfp).
There's no good reason for low_order_gfp, high_order_gfp to be static
rewritable variables.
For this instance, I would go farther and suggest you may want
__GFP_RETRY_MAYFAIL | __GFP_NOWARN to prevent userspace from triggering
the lowmemkiller/oomkiller here.
(I would kill low_order_gfp_flags / high_order_gfp_flags and avoid the
obfuscation.)
-Chris
On 01/05/2018 11:36 AM, Chris Wilson wrote:
> Quoting Laura Abbott (2018-01-05 19:14:08)
>> syzbot reported a warning from Ion:
>>
>> WARNING: CPU: 1 PID: 3485 at mm/page_alloc.c:3926
>>
>> ...
>> __alloc_pages_nodemask+0x9fb/0xd80 mm/page_alloc.c:4252
>> alloc_pages_current+0xb6/0x1e0 mm/mempolicy.c:2036
>> alloc_pages include/linux/gfp.h:492 [inline]
>> ion_system_contig_heap_allocate+0x40/0x2c0
>> drivers/staging/android/ion/ion_system_heap.c:374
>> ion_buffer_create drivers/staging/android/ion/ion.c:93 [inline]
>> ion_alloc+0x2c1/0x9e0 drivers/staging/android/ion/ion.c:420
>> ion_ioctl+0x26d/0x380 drivers/staging/android/ion/ion-ioctl.c:84
>> vfs_ioctl fs/ioctl.c:46 [inline]
>> do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
>> SYSC_ioctl fs/ioctl.c:701 [inline]
>> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>>
>> This is a warning about attempting to allocate order > MAX_ORDER. This
>> is coming from a userspace Ion allocation request. Since userspace is
>> free to request however much memory it wants (and the kernel is free to
>> deny its allocation), silence the allocation attempt with __GFP_NOWARN
>> in case it fails.
>>
>> Reported-by: [email protected]
>> Reported-by: syzbot <[email protected]>
>> Signed-off-by: Laura Abbott <[email protected]>
>> ---
>> drivers/staging/android/ion/ion_system_heap.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
>> index 71c4228f8238..bc19cdd30637 100644
>> --- a/drivers/staging/android/ion/ion_system_heap.c
>> +++ b/drivers/staging/android/ion/ion_system_heap.c
>> @@ -362,7 +362,7 @@ static int ion_system_contig_heap_allocate(struct ion_heap *heap,
>> unsigned long i;
>> int ret;
>>
>> - page = alloc_pages(low_order_gfp_flags, order);
>> + page = alloc_pages(low_order_gfp_flags | __GFP_NOWARN, order);
>
> There's both high_order_gfp and low_order_gfp. The former includes
> NOWARN and NORETRY.
>
> Interesting, ion_system_heap_create_pools() tries to mix low_order and
> high_order, but it only ever uses high_order flags. (orders[0] == 8
> forcing a permanent switch from low_order_gfp to high_order_gfp).
>
Good find, that got lost in a refactor back in 4.9.
> There's no good reason for low_order_gfp, high_order_gfp to be static
> rewritable variables.
>
> For this instance, I would go farther and suggest you may want
> __GFP_RETRY_MAYFAIL | __GFP_NOWARN to prevent userspace from triggering
> the lowmemkiller/oomkiller here.
>
> (I would kill low_order_gfp_flags / high_order_gfp_flags and avoid the
> obfuscation.)
> -Chris
>
Yeah, I think this all needs some refactoring. The high_order/low_order
flags were originally for the system heap to allocate pages for the
page pool and I don't think they should be reused for the contig heap.
I'll see about doing a refactor.
Thanks for the review!
Laura