linux-kernel - Re: Potential NULL pointer deference in drm/amdgpu

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Date:   Thu, 10 Oct 2019 06:52:29 +0000
From:   "Koenig, Christian" <Christian.Koenig@....com>
To:     Yizhuo Zhai <yzhai003@....edu>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>,
        "Quan, Evan" <Evan.Quan@....com>, "Xiao, Jack" <Jack.Xiao@....com>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Zhiyun Qian <zhiyunq@...ucr.edu>,
        Chengyu Song <csong@...ucr.edu>
Subject: Re: Potential NULL pointer deference in drm/amdgpu

Hi Yizhuo,

Am 10.10.19 um 07:09 schrieb Yizhuo Zhai:
> Hi All:
> drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c:
> The function to_amdgpu_fence() could return NULL, but callers
> in this file does not check the return value but directly dereference it,
> which seems potentially unsafe.
> Such callers include amdgpu_fence_get_timeline_name(),
> amdgpu_fence_enable_signaling() and amdgpu_fence_free().

That is expected behavior and no need to worry.

The functions in amdgpu_fence.c are the callbacks to implement 
amdgpu_fence_ops. The function to_amdgpu_fence() checks if the ops of 
the fence are amdgpu_fence_ops, so it is guaranteed that the functions 
are called with an amdgpu_fence structure.

Regards,
Christian.