> +     if (!entity->rq)
> +             return 0;
> +

Yes, supposedly we shouldn't get 'entity->rq == NULL' case , that looks the 
true bug 

-----邮件原件-----
发件人: amd-gfx <[email protected]> 代表 Christian K?nig
发送时间: 2020年2月19日 18:50
收件人: Zhang, Hawking <[email protected]>; Li, Dennis <[email protected]>; 
[email protected]; Deucher, Alexander <[email protected]>; 
Zhou1, Tao <[email protected]>; Chen, Guchun <[email protected]>
主题: Re: [PATCH] drm/amdgpu: fix a bug NULL pointer dereference

Well of hand this patch looks like a clear NAK to me.

Returning without raising an error is certainly the wrong thing to do here 
because we just drop the necessary page table updates.

How does the entity->rq ends up as NULL in the first place?

Regards,
Christian.

Am 19.02.20 um 07:26 schrieb Zhang, Hawking:
> [AMD Official Use Only - Internal Distribution Only]
>
> Reviewed-by: Hawking Zhang <[email protected]>
>
> Regards,
> Hawking
> -----Original Message-----
> From: Dennis Li <[email protected]>
> Sent: Wednesday, February 19, 2020 12:05
> To: [email protected]; Deucher, Alexander 
> <[email protected]>; Zhou1, Tao <[email protected]>; Zhang, 
> Hawking <[email protected]>; Chen, Guchun <[email protected]>
> Cc: Li, Dennis <[email protected]>
> Subject: [PATCH] drm/amdgpu: fix a bug NULL pointer dereference
>
> check whether the queue of entity is null to avoid null pointer dereference.
>
> Change-Id: I08d56774012cf229ba2fe7a011c1359e8d1e2781
> Signed-off-by: Dennis Li <[email protected]>
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c 
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c
> index 4cc7881f438c..67cca463ddcc 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c
> @@ -95,6 +95,9 @@ static int amdgpu_vm_sdma_commit(struct 
> amdgpu_vm_update_params *p,
>       int r;
>   
>       entity = p->direct ? &p->vm->direct : &p->vm->delayed;
> +     if (!entity->rq)
> +             return 0;
> +
>       ring = container_of(entity->rq->sched, struct amdgpu_ring, sched);
>   
>       WARN_ON(ib->length_dw == 0);
> --
> 2.17.1
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