[PATCH v2 4/7] drm/amdgpu: Fix out-of-bounds issue in user fence

[Paneer Selvam, Arunpravin]

Hi Christian,


On 12/13/2024 4:13 PM, Christian König wrote:
> Am 12.12.24 um 15:25 schrieb Arunpravin Paneer Selvam:
>> Fix out-of-bounds issue in userq fence create when
>> accessing the userq xa structure. Added a lock to
>> protect the race condition.
>>
>> BUG: KASAN: slab-out-of-bounds in 
>> amdgpu_userq_fence_create+0x726/0x880 [amdgpu]
>> [  +0.000006] Call Trace:
>> [  +0.000005]  <TASK>
>> [  +0.000005]  dump_stack_lvl+0x6c/0x90
>> [  +0.000011]  print_report+0xc4/0x5e0
>> [  +0.000009]  ? srso_return_thunk+0x5/0x5f
>> [  +0.000008]  ? kasan_complete_mode_report_info+0x26/0x1d0
>> [  +0.000007]  ? amdgpu_userq_fence_create+0x726/0x880 [amdgpu]
>> [  +0.000405]  kasan_report+0xdf/0x120
>> [  +0.000009]  ? amdgpu_userq_fence_create+0x726/0x880 [amdgpu]
>> [  +0.000405]  __asan_report_store8_noabort+0x17/0x20
>> [  +0.000007]  amdgpu_userq_fence_create+0x726/0x880 [amdgpu]
>> [  +0.000406]  ? __pfx_amdgpu_userq_fence_create+0x10/0x10 [amdgpu]
>> [  +0.000408]  ? srso_return_thunk+0x5/0x5f
>> [  +0.000008]  ? ttm_resource_move_to_lru_tail+0x235/0x4f0 [ttm]
>> [  +0.000013]  ? srso_return_thunk+0x5/0x5f
>> [  +0.000008]  amdgpu_userq_signal_ioctl+0xd29/0x1c70 [amdgpu]
>> [  +0.000412]  ? __pfx_amdgpu_userq_signal_ioctl+0x10/0x10 [amdgpu]
>> [  +0.000404]  ? try_to_wake_up+0x165/0x1840
>> [  +0.000010]  ? __pfx_futex_wake_mark+0x10/0x10
>> [  +0.000011]  drm_ioctl_kernel+0x178/0x2f0 [drm]
>> [  +0.000050]  ? __pfx_amdgpu_userq_signal_ioctl+0x10/0x10 [amdgpu]
>> [  +0.000404]  ? __pfx_drm_ioctl_kernel+0x10/0x10 [drm]
>> [  +0.000043]  ? __kasan_check_read+0x11/0x20
>> [  +0.000007]  ? srso_return_thunk+0x5/0x5f
>> [  +0.000007]  ? __kasan_check_write+0x14/0x20
>> [  +0.000008]  drm_ioctl+0x513/0xd20 [drm]
>> [  +0.000040]  ? __pfx_amdgpu_userq_signal_ioctl+0x10/0x10 [amdgpu]
>> [  +0.000407]  ? __pfx_drm_ioctl+0x10/0x10 [drm]
>> [  +0.000044]  ? srso_return_thunk+0x5/0x5f
>> [  +0.000007]  ? _raw_spin_lock_irqsave+0x99/0x100
>> [  +0.000007]  ? __pfx__raw_spin_lock_irqsave+0x10/0x10
>> [  +0.000006]  ? __rseq_handle_notify_resume+0x188/0xc30
>> [  +0.000008]  ? srso_return_thunk+0x5/0x5f
>> [  +0.000008]  ? srso_return_thunk+0x5/0x5f
>> [  +0.000006]  ? _raw_spin_unlock_irqrestore+0x27/0x50
>> [  +0.000010]  amdgpu_drm_ioctl+0xcd/0x1d0 [amdgpu]
>> [  +0.000388]  __x64_sys_ioctl+0x135/0x1b0
>> [  +0.000009]  x64_sys_call+0x1205/0x20d0
>> [  +0.000007]  do_syscall_64+0x4d/0x120
>> [  +0.000008]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
>> [  +0.000007] RIP: 0033:0x7f7c3d31a94f
>>
>> Signed-off-by: Arunpravin Paneer Selvam 
>> <Arunpravin.PaneerSelvam at amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
>> index 3a88f754a395..49dc78c2f0d7 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
>> @@ -229,6 +229,7 @@ int amdgpu_userq_fence_create(struct 
>> amdgpu_usermode_queue *userq,
>>           unsigned long index, count = 0;
>>           int i = 0;
>>   +        xa_lock(&userq->fence_drv_xa);
>
> Don't you allocate the userq->fence_drv_xa after counting the number 
> of objects?
>
> If yes then you need to drop the lock again for that.
We are allocating  memory for userq_fence->fence_drv_array using the 
kvmalloc_array(),
should we drop the lock for this memory allocation and again acquire the 
lock for
moving the fence_drv references from userq->fence_drv_xa to 
userq_fence->fence_drv_array
code block. Is this correct?
>
>> xa_for_each(&userq->fence_drv_xa, index, stored_fence_drv)
>>               count++;
>>   @@ -240,12 +241,13 @@ int amdgpu_userq_fence_create(struct 
>> amdgpu_usermode_queue *userq,
>>           if (userq_fence->fence_drv_array) {
>>               xa_for_each(&userq->fence_drv_xa, index, 
>> stored_fence_drv) {
>>                   userq_fence->fence_drv_array[i] = stored_fence_drv;
>> -                xa_erase(&userq->fence_drv_xa, index);
>> +                __xa_erase(&userq->fence_drv_xa, index);
>
> It's *much* more efficient to release all entries at once by calling 
> xa_destroy() after the loop I think.
sure, I will try with xa_destroy().

Thanks,
Arun.
>
> Regards,
> Christian.
>
>>                   i++;
>>               }
>>           }
>>             userq_fence->fence_drv_array_count = i;
>> +        xa_unlock(&userq->fence_drv_xa);
>>       } else {
>>           userq_fence->fence_drv_array = NULL;
>>           userq_fence->fence_drv_array_count = 0;
>