[PATCH v4 1/3] drm/amdgpu: Fix out-of-bounds issue in user fence

[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.

v2:(Christian)
  - Allocate memory with GFP_ATOMIC.

v3:
  - Moved to 2 xa approach.

v4:(Christian)
  - Lock the xa_for_each blocks and memory allocation part
    as well to make sure that xa is not modified in between
    the 2 xa_for_each blocks.

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 | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
index 2e7271362ace..5bc86ba77437 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
@@ -229,23 +229,25 @@ int amdgpu_userq_fence_create(struct amdgpu_usermode_queue *userq,
 		unsigned long index, count = 0;
 		int i = 0;
 
+		xa_lock(&userq->fence_drv_xa);
 		xa_for_each(&userq->fence_drv_xa, index, stored_fence_drv)
 			count++;
 
 		userq_fence->fence_drv_array =
 			kvmalloc_array(count,
 				       sizeof(struct amdgpu_userq_fence_driver *),
-				       GFP_KERNEL);
+				       GFP_ATOMIC);
 
 		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);
 				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;
-- 
2.25.1