linux-kernel - Re: [PATCH] drm/amd/amdgpu/amdgpu_cs: fix refcount leak of a dma

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Message-ID: <23d5251f-c910-aed3-5d9e-07d6e5e5add2@amd.com>
Date:   Fri, 21 Jan 2022 08:45:06 +0100
From:   Christian König <christian.koenig@....com>
To:     Xin Xiong <xiongx18@...an.edu.cn>,
        Alex Deucher <alexander.deucher@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linaro-mm-sig@...ts.linaro.org
Cc:     yuanxzhang@...an.edu.cn, Xin Tan <tanxin.ctf@...il.com>
Subject: Re: [PATCH] drm/amd/amdgpu/amdgpu_cs: fix refcount leak of a
 dma_fence obj

Am 21.01.22 um 06:28 schrieb Xin Xiong:
> This issue takes place in an error path in
> amdgpu_cs_fence_to_handle_ioctl(). When `info->in.what` falls into
> default case, the function simply returns -EINVAL, forgetting to
> decrement the reference count of a dma_fence obj, which is bumped
> earlier by amdgpu_cs_get_fence(). This may result in reference count
> leaks.
>
> Fix it by decreasing the refcount of specific object before returning
> the error code.
>
> Signed-off-by: Xin Xiong <xiongx18@...an.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@...il.com>

Good catch. Reviewed-by: Christian König <christian.koenig@....com>

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> index 0311d799a..894869789 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> @@ -1510,6 +1510,7 @@ int amdgpu_cs_fence_to_handle_ioctl(struct drm_device *dev, void *data,
>   		return 0;
>   
>   	default:
> +		dma_fence_put(fence);
>   		return -EINVAL;
>   	}
>   }