in line 1535, "dma_fence_put(fence);" drop the reference to fence and may
cause fence to be released. However, fence is used subsequently in line
1542 "fence->error". This may result in an use-after-free bug.
It can be fixed by recording fence->error in a variable before dropping
the reference to fence and referencing it after dropping.
The bug has been confirmed by Christian König on 2021-08-16. Now, I
resend this patch with my real name. I hope the patch can be updated
in a near future.
Signed-off-by: Wentao_Liang <[email protected]>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index b28af04b0c3e..1d675a5838f2 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -1518,7 +1518,7 @@ static int amdgpu_cs_wait_all_fences(struct amdgpu_device *adev,
struct drm_amdgpu_fence *fences)
{
uint32_t fence_count = wait->in.fence_count;
- unsigned int i;
+ unsigned int i, error;
long r = 1;
for (i = 0; i < fence_count; i++) {
@@ -1533,14 +1533,15 @@ static int amdgpu_cs_wait_all_fences(struct amdgpu_device *adev,
r = dma_fence_wait_timeout(fence, true, timeout);
dma_fence_put(fence);
+ error = fence->error;
if (r < 0)
return r;
if (r == 0)
break;
- if (fence->error)
- return fence->error;
+ if (error)
+ return error;
}
memset(wait, 0, sizeof(*wait));
--
2.25.1
Am 28.07.22 um 14:12 schrieb Wentao_Liang:
> in line 1535, "dma_fence_put(fence);" drop the reference to fence and may
> cause fence to be released. However, fence is used subsequently in line
> 1542 "fence->error". This may result in an use-after-free bug.
>
> It can be fixed by recording fence->error in a variable before dropping
> the reference to fence and referencing it after dropping.
>
> The bug has been confirmed by Christian König on 2021-08-16. Now, I
> resend this patch with my real name. I hope the patch can be updated
> in a near future.
The subject line should be something like "drm/amdgpu: fix potential use
after free".
>
> Signed-off-by: Wentao_Liang <[email protected]>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> index b28af04b0c3e..1d675a5838f2 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> @@ -1518,7 +1518,7 @@ static int amdgpu_cs_wait_all_fences(struct amdgpu_device *adev,
> struct drm_amdgpu_fence *fences)
> {
> uint32_t fence_count = wait->in.fence_count;
> - unsigned int i;
> + unsigned int i, error;
> long r = 1;
>
> for (i = 0; i < fence_count; i++) {
> @@ -1533,14 +1533,15 @@ static int amdgpu_cs_wait_all_fences(struct amdgpu_device *adev,
>
> r = dma_fence_wait_timeout(fence, true, timeout);
> dma_fence_put(fence);
> + error = fence->error;
That's still the wrong order, you need to get the fence error before
dropping the reference.
Christian.
> if (r < 0)
> return r;
>
> if (r == 0)
> break;
>
> - if (fence->error)
> - return fence->error;
> + if (error)
> + return error;
> }
>
> memset(wait, 0, sizeof(*wait));