[PATCH AUTOSEL 5.15 17/24] drm/amdgpu: Fix potential fence use-after-free v2

[Sasha Levin]

From: shanzhulig <shanzhu...@gmail.com>

[ Upstream commit 2e54154b9f27262efd0cb4f903cc7d5ad1fe9628 ]

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 <shanzhu...@gmail.com>
Signed-off-by: Christian König <christian.koe...@amd.com>
Reviewed-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 2fd4d8ad7e40d..4b01188385b28 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -1541,15 +1541,15 @@ 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));
-- 
2.39.2