Re: [PATCH] drm/amdkfd: fix potential null pointer dereference on pointer peer_dev

[Kuehling, Felix]

I think this could happen if KFD initialization fails for a device. 
Currently we'd add the device, and then remove it again. That may leave 
a gap in the proximity domains. Oak just had a fix recently to clean 
that up by only adding KFD devices to the topology after successful 
initialization.

Regards,
 Â Felix

On 2019-07-02 11:29 a.m., Liu, Shaoyun wrote:
>   From the comments , "we will loop GPUs that already be processed (with
> lower value of proximity_domain) ", the device should already been
> added into the topology_device_list. So in this case ,
> kfd_topology_device_by_proximity_domain will not return a NULL pointer.
> If you really get the null pointer dereferences here , we must have
> some bigger problem and can not solved by added the null check here.
>
> Regards
>
> shaoyun.liu
>
> On 2019-06-29 9:31 a.m., Colin King wrote:
>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>>
>> The call to kfd_topology_device_by_proximity_domain can return a NULL
>> pointer so add a null pointer check on peer_dev to the existing null
>> pointer check on peer_dev->gpu to avoid any potential null pointer
>> dereferences.
>>
>> Addresses-Coverity: ("Dereference on null return value")
>> Fixes: ae9a25aea7f3 ("drm/amdkfd: Generate xGMI direct iolink")
>> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>> ---
>>    drivers/gpu/drm/amd/amdkfd/kfd_crat.c | 2 +-
>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
>> index 4e3fc284f6ac..cb6b46cfa6c2 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
>> @@ -1293,7 +1293,7 @@ static int kfd_create_vcrat_image_gpu(void *pcrat_image,
>>    	if (kdev->hive_id) {
>>    		for (nid = 0; nid < proximity_domain; ++nid) {
>>    			peer_dev = kfd_topology_device_by_proximity_domain(nid);
>> -			if (!peer_dev->gpu)
>> +			if (!peer_dev || !peer_dev->gpu)
>>    				continue;
>>    			if (peer_dev->gpu->hive_id != kdev->hive_id)
>>    				continue;
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