linux-kernel - Re: [RFC PATCH 0/3] Clean up locking in hugetlb faulting code

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] [day] [month] [year] [list]

Message-ID: <bd137e8b-aca7-4c5d-a8a0-898a0762ccd1@igalia.com>
Date: Mon, 16 Jun 2025 11:21:26 +0800
From: Gavin Guo <gavinguo@...lia.com>
To: Oscar Salvador <osalvador@...e.de>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Muchun Song <muchun.song@...ux.dev>, David Hildenbrand
 <david@...hat.com>, James Houghton <jthoughton@...gle.com>,
 Peter Xu <peterx@...hat.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/3] Clean up locking in hugetlb faulting code

Hi Oscar,

On 6/2/25 22:16, Oscar Salvador wrote:
> Hi all,
> 
> This RFC is the culmination of the discussion that happened in [1].
> TLDR: No one really knew what the locks were protecting us against, and
> whether we needed them at all.
> 
> Some reasearch showed that most of them were introduced in a time were
> truncation was not serialized with the mutex, as it is today, so we were
> relying on the lock for the page to not go away from the pagecache.
> More details can be find in patch#1.
> 
> This is for the locks, but I also started to look at the references
> we take in hugetlb_fault and hugetlb_wp as it seems to me we are taking
> more than actually needed, but that is once we manage to sort this out.
> 
> I ran hugetlb LTP tests and nothing screamed, and I also plan to run selftests
> later on.
> 
> @Galvin. Could you please run your syzkaller with this patchset applied and
> see whether you can trigger something?

Sorry for the late response. My capacity is limited in the last two 
weeks of joining an event and didn't notice the talk. And it seems 
already huge discussions and good progress. Currently, I saw the 
discussion is in another latest thread: 
https://lore.kernel.org/linux-mm/20250612134701.377855-1-osalvador@suse.de/

Please let me know if the testing is still useful.

> 
> Special thanks to David and Peter Xu that were helping out with this mess.
> 
> [1] https://lore.kernel.org/linux-mm/aDeBUXCRLRZobHq0@localhost.localdomain/T/#md02880ebc2c679678b7f326c5e9e93992428e124
> 
> Oscar Salvador (3):
>    mm, hugetlb: Clean up locking in hugetlb_fault and hugetlb_wp
>    mm, hugetlb: Update comments in hugetlb_fault
>    mm, hugetlb: Drop unlikelys from hugetlb_fault
> 
>   include/linux/hugetlb.h |  12 +++++
>   mm/hugetlb.c            | 117 +++++++++++++++++-----------------------
>   2 files changed, 62 insertions(+), 67 deletions(-)