[PATCH] drm/amdgpu: : Fix the null pointer dereference for amdgpu_device_switch_gang

[Zhou, Bob]

[AMD Official Use Only - AMD Internal Distribution Only]

Hi Christian

Thanks for your comments.
I miss the before logic has limited the generated pointer.

Regards,
Bob

-----Original Message-----
From: Koenig, Christian <Christian.Koenig at amd.com>
Sent: 2024年7月3日 17:26
To: Zhou, Bob <Bob.Zhou at amd.com>; amd-gfx at lists.freedesktop.org; Huang, Tim <Tim.Huang at amd.com>; Zhang, Jesse(Jie) <Jesse.Zhang at amd.com>
Cc: Deucher, Alexander <Alexander.Deucher at amd.com>
Subject: Re: [PATCH] drm/amdgpu: : Fix the null pointer dereference for amdgpu_device_switch_gang

Am 03.07.24 um 11:01 schrieb Bob Zhou:
> To avoid null pointer dereference reported by Coverity, so add null
> pointer check for the return of amdgpu_device_get_gang().

NAK, that's complete nonsense in the first place.

The pointer is guaranteed to be never NULL or otherwise the logic would have crashed long before.

Regards,
Christian.

>
> Signed-off-by: Bob Zhou <bob.zhou at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index bcacf2e35eba..c1d82c346daa 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -6569,7 +6569,7 @@ struct dma_fence *amdgpu_device_switch_gang(struct amdgpu_device *adev,
>               if (old == gang)
>                       break;
>
> -             if (!dma_fence_is_signaled(old))
> +             if (!old || !dma_fence_is_signaled(old))
>                       return old;
>
>       } while (cmpxchg((struct dma_fence __force **)&adev->gang_submit,