Re: [PATCH] mm: prepare anon_vma before swapin rmap

[Vlastimil Babka (SUSE)]

On 4/17/26 15:03, Matthew Wilcox wrote:
> On Fri, Apr 17, 2026 at 01:57:59PM +0200, David Hildenbrand (Arm) wrote:
>> On 4/17/26 12:53, David Hildenbrand (Arm) wrote:
>> > On 4/17/26 03:16, ZhengYuan Huang wrote:
>> >> [BUG]
>> >> madvise(MADV_HWPOISON) can fault a swap entry back in through
>> >> get_user_pages_fast() and hit:
> ...
>> >> I can reproduce this issue deterministically on v6.18, but I have not
>> >> been able to reproduce it with the same setup on next-20260415.
>> 
>> Just speculating, we had
>> 
>> commit 3b617fd3d317bf9dd7e2c233e56eafef05734c9d
>> Author: Lorenzo Stoakes <ljs@xxxxxxxxxx>
>> Date:   Mon Jan 5 20:11:49 2026 +0000
>> 
>>     mm/vma: enforce VMA fork limit on unfaulted,faulted mremap merge too
>> 
>> Go into v6.19.
>> 
>> Maybe there was a scenario where we could have lost vma->anon_vma during
>> a merge, resulting in a swapped page in an anon_vma.
>> 
>> If this cannot be reproduced on 6.19+,there is nothing to worry about.
> 
> ... except that 6.18 is LTS so we need a fix for that kernel version.

It's there: https://kernel.dance/#3b617fd3d317bf9dd7e2c233e56eafef05734c9d

> And maybe 6.12 as well (a373baed5a9d went into 6.9, so no need to
> go further back than that)

Not there (yet?) but it was tagged stable.