Re: mm, something wring in page_lock_anon_vma_read()?

From: Hugh Dickins
Date: Fri May 19 2017 - 22:41:00 EST

On Sat, 20 May 2017, Xishi Qiu wrote:
> Here is a bug report form redhat:
> 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
in Red Hat's kernel-3.10.0-229.4.2.el7 that might happen.