* Re: [PATCH] drivers:gpu:drm:amd:amdgpu:fix a potential use-after-free
[not found] <tencent_D167B6522B17C0228524C70F9CA5EEBBEC09@qq.com>
@ 2021-08-16 6:08 ` Christian König
0 siblings, 0 replies; only message in thread
From: Christian König @ 2021-08-16 6:08 UTC (permalink / raw)
To: lwt105, alexander.deucher
Cc: christian.koenig, Xinhui.Pan, airlied, daniel, sumit.semwal,
nirmoy.das, chenli, JinhuiEric.Huang, mh12gx2825, lee.jones,
kevin1.wang, luben.tuikov, amd-gfx, dri-devel, linux-kernel,
linux-media, linaro-mm-sig
Am 13.08.21 um 05:28 schrieb lwt105:
> in line 1503, "dma_fence_put(fence);" drop the reference to fence and may
> cause fence to be released. However, fence is used subsequently in line
> 1510 "fence->error". This may result in an use-after-free bug.
>
> It can be fixed by recording fence->error in an variable before dropping
> the reference to fence and referencing it after dropping.
>
> Signed-off-by: lwt105 <3061522931@qq.com>
Good catch.
> ---
> 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 30fa1f61e0e5..99d03180e113 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> @@ -1486,7 +1486,7 @@ 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;
Would be nice to have if you could reuse the "r" variable here instead
of a new one.
Regards,
Christian.
>
> for (i = 0; i < fence_count; i++) {
> @@ -1500,6 +1500,7 @@ static int amdgpu_cs_wait_all_fences(struct amdgpu_device *adev,
> continue;
>
> r = dma_fence_wait_timeout(fence, true, timeout);
> + error = fence->error;
> dma_fence_put(fence);
> if (r < 0)
> return r;
> @@ -1507,8 +1508,8 @@ static int amdgpu_cs_wait_all_fences(struct amdgpu_device *adev,
> if (r == 0)
> break;
>
> - if (fence->error)
> - return fence->error;
> + if (error)
> + return error;
> }
>
> memset(wait, 0, sizeof(*wait));
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