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

[Christian König]

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.

>   		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.

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;