linux-kernel - Re: [PATCH] Staging: drivers/gpu/drm/amd/amdgpu: Fix null pointer deference in amdkfd_fence_get_timeline

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Message-ID: <ae062c07-dc09-4975-ad31-2f9d9ea435f9@amd.com>
Date: Fri, 20 Sep 2024 20:58:33 +0200
From: Christian König <christian.koenig@....com>
To: Dipendra Khadka <kdipendra88@...il.com>
Cc: Felix.Kuehling@....com, alexander.deucher@....com, Xinhui.Pan@....com,
 airlied@...il.com, daniel@...ll.ch, amd-gfx@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Staging: drivers/gpu/drm/amd/amdgpu: Fix null pointer
 deference in amdkfd_fence_get_timeline_name

Am 20.09.24 um 18:31 schrieb Dipendra Khadka:
> On Fri, 20 Sept 2024 at 16:01, Christian König <christian.koenig@....com> wrote:
>> Am 20.09.24 um 11:09 schrieb Dipendra Khadka:
>>> '''
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c:108:9: error: Null pointer dereference: fence [nullPointer]
>>>    return fence->timeline_name;
>>>           ^
>>> '''
>>>
>>> The method to_amdgpu_amdkfd_fence can return NULL incase of empty f
>>> or f->ops != &amdkfd_fence_ops.Hence, check has been added .
>>> If fence is null , then null is returned.
>> Well NAK, completely nonsense. Calling the function with a NULL fence is
>> illegal.
> Thanks for enlightening me .

Well sorry to be so direct, but what the heck did you tried to do here?

I mean that is broken on so many different levels that I can't 
understand why somebody is suggesting something like that.

Regards,
Christian.

>
>> Regards,
>> Christian.
>>
>>> Signed-off-by: Dipendra Khadka <kdipendra88@...il.com>
>>> ---
>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c | 3 +++
>>>    1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c
>>> index 1ef758ac5076..2313babcc944 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c
>>> @@ -105,6 +105,9 @@ static const char *amdkfd_fence_get_timeline_name(struct dma_fence *f)
>>>    {
>>>        struct amdgpu_amdkfd_fence *fence = to_amdgpu_amdkfd_fence(f);
>>>
>>> +     if (!fence)
>>> +             return NULL;
>>> +
>>>        return fence->timeline_name;
>>>    }
>>>
> Regards,
> Dipendra Khadka