[PATCH v4 08/23] vfio, mm: fix get_user_pages_remote() and FOLL_LONGTERM

[John Hubbard]

On 11/13/19 11:17 AM, Ira Weiny wrote:
...
>>> @@ -348,33 +347,13 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
>>>   		flags |= FOLL_WRITE;
>>>   
>>>   	down_read(&mm->mmap_sem);
>>> -	if (mm == current->mm) {
>>> -		ret = get_user_pages(vaddr, 1, flags | FOLL_LONGTERM, page,
>>> -				     vmas);
>>> -	} else {
>>> -		ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags, page,
>>> -					    vmas, NULL);
>>> -		/*
>>> -		 * The lifetime of a vaddr_get_pfn() page pin is
>>> -		 * userspace-controlled. In the fs-dax case this could
>>> -		 * lead to indefinite stalls in filesystem operations.
>>> -		 * Disallow attempts to pin fs-dax pages via this
>>> -		 * interface.
>>> -		 */
>>> -		if (ret > 0 && vma_is_fsdax(vmas[0])) {
>>> -			ret = -EOPNOTSUPP;
>>> -			put_page(page[0]);
>>> -		}
>>> -	}
>>> -	up_read(&mm->mmap_sem);
>>> -
>>> +	ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags | FOLL_LONGTERM,
>>> +				    page, NULL, NULL);
>>>   	if (ret == 1) {
>>>   		*pfn = page_to_pfn(page[0]);
>>>   		return 0;
>>
>> Mind the return with the lock held this needs some goto unwind
> 
> Ah yea...  retract my reviewed by...  :-(
> 

ooops, embarrassed that I missed that, good catch. Will repost with it fixed.



thanks,
-- 
John Hubbard
NVIDIA