drm/amdgpu: Fix potential fence use-after-free v2

fence Decrements the reference count before exiting.
Avoid Race Vulnerabilities for fence use-after-free.

v2 (chk): actually fix the use after free and not just move it.

Signed-off-by: shanzhulig <shanzhulig@gmail.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index b34f9f8..040f4cb 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -1654,15 +1654,15 @@ static int amdgpu_cs_wait_all_fences(struct amdgpu_device *adev,
                        continue;
 
                r = dma_fence_wait_timeout(fence, true, timeout);
+               if (r > 0 && fence->error)
+                       r = fence->error;
+
                dma_fence_put(fence);
                if (r < 0)
                        return r;
 
                if (r == 0)
                        break;
-
-               if (fence->error)
-                       return fence->error;
        }
 
        memset(wait, 0, sizeof(*wait));