Re: [PATCH] drm/ttm: fix null-ptr-deref in radeon_ttm_tt_populate()

[Nikita Zhandarovich]

On 4/17/23 07:42, Christian König wrote:
> 
> 
> Am 17.04.23 um 16:34 schrieb Nikita Zhandarovich:
>> Currently, drm_prime_sg_to_page_addr_arrays() dereferences 'gtt->ttm'
>> without ensuring that 'gtt' (and therefore 'gtt->tmm') is not NULL.
>>
>> Fix this by testing 'gtt' for NULL value before dereferencing.
>>
>> Found by Linux Verification Center (linuxtesting.org) with static
>> analysis tool SVACE.
>>
>> Fixes: 40f5cf996991 ("drm/radeon: add PRIME support (v2)")
>> Signed-off-by: Nikita Zhandarovich <n.zhandarovich@xxxxxxxxxx>
>> ---
>>   drivers/gpu/drm/radeon/radeon_ttm.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c
>> b/drivers/gpu/drm/radeon/radeon_ttm.c
>> index 1e8e287e113c..33d01c3bdee4 100644
>> --- a/drivers/gpu/drm/radeon/radeon_ttm.c
>> +++ b/drivers/gpu/drm/radeon/radeon_ttm.c
>> @@ -553,7 +553,7 @@ static int radeon_ttm_tt_populate(struct
>> ttm_device *bdev,
>>           return 0;
>>       }
>>   -    if (slave && ttm->sg) {
>> +    if (gtt && slave && ttm->sg) {
> 
> The gtt variable is derived from the ttm variable and so never NULL
> here. The only case when this can be NULL is for AGP and IIRC we don't
> support DMA-buf in this case.
> 
>>           drm_prime_sg_to_dma_addr_array(ttm->sg, gtt->ttm.dma_address,
> 
> Just use ttm->dma_addresses instead of gtt->ttm.dma_address here to make
> your automated checker happy.
> 
> Regards,
> Christian.
> 
>>                              ttm->num_pages);
>>           return 0;
> 

Thank you for your reply, you are absolutely right.
Apologies for wasting your time.

Nikita