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

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Date:   Fri, 21 Jan 2022 15:48:13 -0500
From:   Alex Deucher <alexdeucher@...il.com>
To:     Christian König <christian.koenig@....com>
Cc:     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 list <amd-gfx@...ts.freedesktop.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-media <linux-media@...r.kernel.org>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@...ts.linaro.org>, Xin Tan <tanxin.ctf@...il.com>,
        yuanxzhang@...an.edu.cn
Subject: Re: [PATCH] drm/amd/amdgpu/amdgpu_cs: fix refcount leak of a
 dma_fence obj

On Fri, Jan 21, 2022 at 2:45 AM Christian König
<christian.koenig@....com> wrote:
>
> 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>

Applied manually.  Strangely I never got this on any of my emails, and
I don't see it in the archives.

Alex

>
> > ---
> >   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;
> >       }
> >   }
>