Re: [PATCH] mm: mempolicy: fix the wrong return value and potential pages leak of mbind

["Li Xinhai" <lixinhai.lxh@gmail.com>]

On 2019-10-31 at 12:31 Andrew Morton wrote:
>On Wed, 30 Oct 2019 11:14:58 -0700 Yang Shi <yang.shi@linux.alibaba.com> wrote:
>
>> On 10/30/19 9:58 AM, Yang Shi wrote:
>> > The commit d883544515aa ("mm: mempolicy: make the behavior consistent
>> > when MPOL_MF_MOVE* and MPOL_MF_STRICT were specified") fixed the return
>> > value of mbind() for a couple of corner cases.  But, it altered the
>> > errno for some other cases, for example, mbind() should return -EFAULT
>> > when part or all of the memory range specified by nodemask and maxnode
>> > points  outside your accessible address space, or there was an unmapped
>> > hole in the specified memory range specified by addr and len.
>> >
>> > Fixed this by preserving the errno returned by queue_pages_range().
>> > And, the pagelist may be not empty even though queue_pages_range()
>> > returns error, put the pages back to LRU since mbind_range() is not called
>> > to really apply the policy so those pages should not be migrated, this
>> > is also the old behavior before the problematic commit.
>> Forgot fixes tag.
>>
>> Fixes: d883544515aa ("mm: mempolicy: make the behavior consistent when
>> MPOL_MF_MOVE* and MPOL_MF_STRICT were specified")
>
>What's the relationship between this patch and
>http://lkml.kernel.org/r/201910291756045288126@gmail.com?
> 

They are for different issues. I found that -EFAULT is hidden from user space by 
d883544515aa when I was fixing the unmapped hole issue which is described in 
your quoted link.

Now, it is fixed for by current commit in this mail thread. I will explain the other 
one in its thead. 

- Xinhai