linux-kernel - Re: [PATCH v2] fs: try an opportunistic lookup for O

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: <20240814024057.GP13701@ZenIV>
Date: Wed, 14 Aug 2024 03:40:57 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: Jeff Layton <jlayton@...nel.org>
Cc: Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mateusz Guzik <mjguzik@...il.com>,
	Josef Bacik <josef@...icpanda.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] fs: try an opportunistic lookup for O_CREAT opens too

On Wed, Aug 14, 2024 at 03:18:17AM +0100, Al Viro wrote:

> That's not the only problem; your "is it negative" test is inherently
> racy in RCU mode.  IOW, what is positive at the time you get here can
> bloody well go negative immediately afterwards.  Hit that with
> O_CREAT and you've got a bogus ENOENT...

Hmm...  OTOH, in that case you end up in step_into(), which will do the
right thing...

	How well does that series survive NFS client regression tests?
That's where I'd expect potentially subtle shite, what with short-circuited
->d_revalidate() on the final pathwalk step in open()...