linux-kernel - Re: [PATCH mm-new 1/1] mm/khugepaged: abort collapse scan on non-swap entries

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1282de5a-3dce-443d-91d1-111103140973@redhat.com>
Date: Wed, 24 Sep 2025 12:10:47 +0200
From: David Hildenbrand <david@...hat.com>
To: Lance Yang <lance.yang@...ux.dev>, akpm@...ux-foundation.org
Cc: lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, baohua@...nel.org,
 baolin.wang@...ux.alibaba.com, dev.jain@....com, hughd@...gle.com,
 ioworker0@...il.com, kirill@...temov.name, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, mpenttil@...hat.com, npache@...hat.com,
 ryan.roberts@....com, ziy@...dia.com, richard.weiyang@...il.com
Subject: Re: [PATCH mm-new 1/1] mm/khugepaged: abort collapse scan on non-swap
 entries

On 24.09.25 12:02, Lance Yang wrote:
> From: Lance Yang <lance.yang@...ux.dev>
> 
> The existing check in hpage_collapse_scan_pmd() is specific to uffd-wp
> markers. Other special markers (e.g., GUARD, POISONED) would not be caught
> early, leading to failures deeper in the swap-in logic.
> 
> hpage_collapse_scan_pmd()
>   `- collapse_huge_page()
>       `- __collapse_huge_page_swapin() -> fails!
> 
> As David suggested[1], this patch skips any such non-swap entries early.
> If a special marker is found, the scan is aborted immediately with the
> SCAN_PTE_NON_PRESENT result, as Lorenzo suggested[2], avoiding wasted
> work.

Note that I suggested to skip all non-present entries except swap 
entries, which includes migration entries, hwpoisoned entries etc.

-- 
Cheers

David / dhildenb