linux-kernel - Re: [PATCH v1 5/6] memcg-v1: no need for memcg locking for MGLRU

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: <ZykEtcHrQRq-KrBC@google.com>
Date: Mon, 4 Nov 2024 10:30:29 -0700
From: Yu Zhao <yuzhao@...gle.com>
To: Shakeel Butt <shakeel.butt@...ux.dev>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Muchun Song <muchun.song@...ux.dev>,
	Hugh Dickins <hughd@...gle.com>,
	Yosry Ahmed <yosryahmed@...gle.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
	Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH v1 5/6] memcg-v1: no need for memcg locking for MGLRU

On Sat, Oct 26, 2024 at 09:26:04AM -0600, Yu Zhao wrote:
> On Sat, Oct 26, 2024 at 12:34 AM Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> >
> > On Thu, Oct 24, 2024 at 06:23:02PM GMT, Shakeel Butt wrote:
> > > While updating the generation of the folios, MGLRU requires that the
> > > folio's memcg association remains stable. With the charge migration
> > > deprecated, there is no need for MGLRU to acquire locks to keep the
> > > folio and memcg association stable.
> > >
> > > Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
> >
> > Andrew, can you please apply the following fix to this patch after your
> > unused fixup?
> 
> Thanks!

syzbot caught the following:

  WARNING: CPU: 0 PID: 85 at mm/vmscan.c:3140 folio_update_gen+0x23d/0x250 mm/vmscan.c:3140
  ...

Andrew, can you please fix this in place? Thank you.

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ddaaff67642e..9a610dbff384 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3138,7 +3138,6 @@ static int folio_update_gen(struct folio *folio, int gen)
 	unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
 
 	VM_WARN_ON_ONCE(gen >= MAX_NR_GENS);
-	VM_WARN_ON_ONCE(!rcu_read_lock_held());
 
 	do {
 		/* lru_gen_del_folio() has isolated this page? */