Messages in this thread | | | Date | Tue, 9 Aug 2022 15:28:08 +0200 | Subject | Re: [PATCH] drivers:gpu:drm:amd:amdgpu:amdgpu_cs.c:fix a potential use-after-free | From | Christian König <> |
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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 <Wentao_Liang_g@163.com> > --- > 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));
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