Re: [PATCH] drm/ttm: add a WARN_ON in ttm_set_driver_manager when array bounds (v2)

["Christian König" <christian.koenig@amd.com>]

Well it will crash later on when accessing the invalid offset, so not 
much gained.

But either way works for me.

Christian.

Am 13.09.21 um 04:35 schrieb Chen, Guchun:
> [Public]
>
> Thanks for your suggestion, Robin. Do you agree with this as well, Christian and Xinhui?
>
> Regards,
> Guchun
>
> -----Original Message-----
> From: Robin Murphy <robin.murphy@arm.com>
> Sent: Saturday, September 11, 2021 2:25 AM
> To: Chen, Guchun <Guchun.Chen@amd.com>; amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; Koenig, Christian <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; Deucher, Alexander <Alexander.Deucher@amd.com>
> Cc: Shi, Leslie <Yuliang.Shi@amd.com>
> Subject: Re: [PATCH] drm/ttm: add a WARN_ON in ttm_set_driver_manager when array bounds (v2)
>
> On 2021-09-10 11:09, Guchun Chen wrote:
>> Vendor will define their own memory types on top of TTM_PL_PRIV, but
>> call ttm_set_driver_manager directly without checking mem_type value
>> when setting up memory manager. So add such check to aware the case
>> when array bounds.
>>
>> v2: lower check level to WARN_ON
>>
>> Signed-off-by: Leslie Shi <Yuliang.Shi@amd.com>
>> Signed-off-by: Guchun Chen <guchun.chen@amd.com>
>> ---
>>    include/drm/ttm/ttm_device.h | 1 +
>>    1 file changed, 1 insertion(+)
>>
>> diff --git a/include/drm/ttm/ttm_device.h
>> b/include/drm/ttm/ttm_device.h index 07d722950d5b..aa79953c807c 100644
>> --- a/include/drm/ttm/ttm_device.h
>> +++ b/include/drm/ttm/ttm_device.h
>> @@ -291,6 +291,7 @@ ttm_manager_type(struct ttm_device *bdev, int mem_type)
>>    static inline void ttm_set_driver_manager(struct ttm_device *bdev, int type,
>>    					  struct ttm_resource_manager *manager)
>>    {
>> +	WARN_ON(type >= TTM_NUM_MEM_TYPES);
> Nit: I know nothing about this code, but from the context alone it would seem sensible to do
>
> 	if (WARN_ON(type >= TTM_NUM_MEM_TYPES))
> 		return;
>
> to avoid making the subsequent assignment when we *know* it's invalid and likely to corrupt memory.
>
> Robin.
>
>>    	bdev->man_drv[type] = manager;
>>    }
>>    
>>