Re: mm, something wring in page_lock_anon_vma_read()?

[Xishi Qiu]

On 2017/5/20 10:40, Hugh Dickins wrote:

> On Sat, 20 May 2017, Xishi Qiu wrote:
>>
>> Here is a bug report form redhat: https://bugzilla.redhat.com/show_bug.cgi?id=1305620
>> And I meet the bug too. However it is hard to reproduce, and 
>> 624483f3ea82598("mm: rmap: fix use-after-free in __put_anon_vma") is not help.
>>
>> From the vmcore, it seems that the page is still mapped(_mapcount=0 and _count=2),
>> and the value of mapping is a valid address(mapping = 0xffff8801b3e2a101),
>> but anon_vma has been corrupted.
>>
>> Any ideas?
> 
> Sorry, no.  I assume that _mapcount has been misaccounted, for example
> a pte mapped in on top of another pte; but cannot begin tell you where

Hi Hugh,

What does "a pte mapped in on top of another pte" mean? Could you give more info?

Thanks,
Xishi Qiu

> in Red Hat's kernel-3.10.0-229.4.2.el7 that might happen.
> 
> Hugh
> 
> .
>