[PATCH] drm/amdkfd: fix a potential cu_mask memory leak

[Felix Kuehling]

On 2021-09-29 7:32 p.m., Yu, Lang wrote:
> [AMD Official Use Only]
>
>
>
>> -----Original Message-----
>> From: Kuehling, Felix <Felix.Kuehling at amd.com>
>> Sent: Wednesday, September 29, 2021 11:25 PM
>> To: Yu, Lang <Lang.Yu at amd.com>; amd-gfx at lists.freedesktop.org
>> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Huang, Ray
>> <Ray.Huang at amd.com>
>> Subject: Re: [PATCH] drm/amdkfd: fix a potential cu_mask memory leak
>>
>> Am 2021-09-29 um 4:22 a.m. schrieb Lang Yu:
>>> If user doesn't explicitly call kfd_ioctl_destroy_queue to destroy all
>>> created queues, when the kfd process is destroyed, some queues'
>>> cu_mask memory are not freed.
>>>
>>> To avoid forgetting to free them in some places, free them immediately
>>> after use.
>>>
>>> Signed-off-by: Lang Yu <lang.yu at amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdkfd/kfd_chardev.c               |  8 ++++----
>>>   drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c | 10
>>> ++++------
>>>   2 files changed, 8 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>> b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>> index 4de907f3e66a..5c0e6dcf692a 100644
>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>> @@ -451,8 +451,8 @@ static int kfd_ioctl_set_cu_mask(struct file *filp, struct
>> kfd_process *p,
>>>   	retval = copy_from_user(properties.cu_mask, cu_mask_ptr,
>> cu_mask_size);
>>>   	if (retval) {
>>>   		pr_debug("Could not copy CU mask from userspace");
>>> -		kfree(properties.cu_mask);
>>> -		return -EFAULT;
>>> +		retval = -EFAULT;
>>> +		goto out;
>>>   	}
>>>
>>>   	mutex_lock(&p->mutex);
>>> @@ -461,8 +461,8 @@ static int kfd_ioctl_set_cu_mask(struct file
>>> *filp, struct kfd_process *p,
>>>
>>>   	mutex_unlock(&p->mutex);
>>>
>>> -	if (retval)
>>> -		kfree(properties.cu_mask);
>>> +out:
>>> +	kfree(properties.cu_mask);
>>>
>>>   	return retval;
>>>   }
>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c
>>> b/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c
>>> index 243dd1efcdbf..4c81d690f31a 100644
>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c
>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c
>>> @@ -394,8 +394,6 @@ int pqm_destroy_queue(struct
>> process_queue_manager *pqm, unsigned int qid)
>>>   			pdd->qpd.num_gws = 0;
>>>   		}
>>>
>>> -		kfree(pqn->q->properties.cu_mask);
>>> -		pqn->q->properties.cu_mask = NULL;
>>>   		uninit_queue(pqn->q);
>>>   	}
>>>
>>> @@ -448,16 +446,16 @@ int pqm_set_cu_mask(struct
>> process_queue_manager *pqm, unsigned int qid,
>>>   		return -EFAULT;
>>>   	}
>>>
>>> -	/* Free the old CU mask memory if it is already allocated, then
>>> -	 * allocate memory for the new CU mask.
>>> -	 */
>>> -	kfree(pqn->q->properties.cu_mask);
>>> +	WARN_ON_ONCE(pqn->q->properties.cu_mask);
>>>
>>>   	pqn->q->properties.cu_mask_count = p->cu_mask_count;
>>>   	pqn->q->properties.cu_mask = p->cu_mask;
>>>
>>>   	retval = pqn->q->device->dqm->ops.update_queue(pqn->q->device->dqm,
>>>   							pqn->q);
>>> +
>>> +	pqn->q->properties.cu_mask = NULL;
>>> +
>> This won't work correctly. We need to save the cu_mask for later.
>> Otherwise the next time dqm->ops.update_queue is called, for example in
>> pqm_update_queue or pqm_set_gws, it will wipe out the CU mask in the MQD.
> Let's just return when meeting a null cu_mask in update_cu_mask() to avoid that.
> Like following,
>
> static void update_cu_mask(struct mqd_manager *mm, void *mqd,
> 			   struct queue_properties *q)
> {
> 	struct v10_compute_mqd *m;
> 	uint32_t se_mask[4] = {0}; /* 4 is the max # of SEs */
>
> 	if (!q-> cu_mask || q->cu_mask_count == 0)
> 		return;
> 	......
> }
>
> Is this fine with you? Thanks!

I think that could work. I still don't like it. It leaves the CU mask in 
the q->properties structure, but it's only ever used temporarily and 
doesn't need to be persistent. I'd argue, in this case, the cu_mask 
shouldn't be in the q->properties structure at all, but should be passed 
as an optional parameter into the dqm->ops.update_queue call.

But I think a simpler fix would be to move the freeing of the CU mask 
into uninit_queue. That would catch all cases where a queue gets 
destroyed, including the process termination case.

Regards,
   Felix


>
> Regards,
> Lang
>   
>> Regards,
>>    Felix
>>
>>
>>>   	if (retval != 0)
>>>   		return retval;
>>>