[PATCH] drm/amdgpu: disallow multiple BO_HANDLES chunks in one submit

[Christian König]

Am 03.07.24 um 14:48 schrieb Pierre-Eric Pelloux-Prayer:
> Le 02/07/2024 à 15:35, Christian König a écrit :
>> Am 02.07.24 um 15:23 schrieb Pierre-Eric Pelloux-Prayer:
>>> Before this commit, only submits with both a BO_HANDLES chunk and a
>>> 'bo_list_handle' would be rejected (by amdgpu_cs_parser_bos).
>>>
>>> But if UMD sent a multiple BO_HANDLES, what would happen is:
>>> * only the last one would be really used
>>> * all the others would leak memory as amdgpu_cs_p1_bo_handles would
>>>    overwrite the previous p->bo_list value
>>>
>>> This commit rejects submissions with multiple BO_HANDLES chunks to
>>> match the implementation of the parser.
>>>
>>> Signed-off-by: Pierre-Eric Pelloux-Prayer 
>>> <pierre-eric.pelloux-prayer at amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 4 ++++
>>>   1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>>> index c08dfffae262..69d168d6f35a 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>>> @@ -154,6 +154,10 @@ static int amdgpu_cs_p1_bo_handles(struct 
>>> amdgpu_cs_parser *p,
>>>       struct drm_amdgpu_bo_list_entry *info;
>>>       int r;
>>> +    /* Disallow multiple BO_HANDLES chunks. */
>>
>> Describe why you do something, instead of what you do since that 
>> should be obvious from the code.
>>
>> E.g. something like /* Only allow a single BO list to avoid memory 
>> leak. */
>
> It's not really to avoid a memleak because the code below could be fixed
> to not leak the list.
> This change is really about only disallowing multiple BO_HANDLES since 
> this is the de-facto API, except it was not validated until now.
>
> I can rephrase the comment as /* Only a single BO list is allowed. */
>
> Would that work?

Mhm, we still need to give a reason why only a single BO list is allowed.

Maybe "Only a single BO list is allowed to simplify handling".

I don't really see a use case for having more than one BO list, but who 
knows.

Regards,
Christian.

>
> Thanks,
> Pierre-Eric
>
>>
>> With that fixed Reviewed-by: Christian König <christian.koenig at amd.com>
>>
>> Regards,
>> Christian.
>>
>>
>>> +    if (p->bo_list)
>>> +        return -EINVAL;
>>> +
>>>       r = amdgpu_bo_create_list_entry_array(data, &info);
>>>       if (r)
>>>           return r;