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([2a02:908:1252:fb60:7d83:fd8:eb16:8605]) by smtp.gmail.com with ESMTPSA id l2sm9347965wme.28.2021.08.15.23.08.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 15 Aug 2021 23:08:18 -0700 (PDT) Subject: Re: [PATCH] drivers:gpu:drm:amd:amdgpu:fix a potential use-after-free To: lwt105 <3061522931@qq.com>, alexander.deucher@amd.com Cc: christian.koenig@amd.com, Xinhui.Pan@amd.com, airlied@linux.ie, daniel@ffwll.ch, sumit.semwal@linaro.org, nirmoy.das@amd.com, chenli@uniontech.com, JinhuiEric.Huang@amd.com, mh12gx2825@gmail.com, lee.jones@linaro.org, kevin1.wang@amd.com, luben.tuikov@amd.com, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org References: From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: Date: Mon, 16 Aug 2021 08:08:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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));