linux-kernel - Re: Union mount and lockdep design issues

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: <87hb6qwc57.fsf@tucsk.pomaz.szeredi.hu>
Date:	Wed, 13 Jul 2011 15:20:04 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	David Howells <dhowells@...hat.com>
Cc:	Michal Suchanek <hramrach@...trum.cz>, Ian Kent <ikent@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ric Wheeler <rwheeler@...hat.com>,
	Alexander Viro <aviro@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jeff Moyer <jmoyer@...hat.com>
Subject: Re: Union mount and lockdep design issues

David Howells <dhowells@...hat.com> writes:

> Miklos Szeredi <miklos@...redi.hu> wrote:
>
>> Overlayfs never locks both upper and lower at the same time, which means
>> there's no AB-BA locking dependency.  The lock orderings are:
>
> What you're talking about is not analogous to the situation I'm seeing with
> unionmount.
>
> You actually have three filesystems in overlayfs.  The interaction between
> overlayfs-and-upperfs and overlayfs-and-lowerfs is the equivalent in
> unionmount terms to upperfs-and-lowerfs.  This is where the lockdep issue
> lies.

Normally overlayfs would be immune to this, since lower/upper are
different filesystem types.  But overlayfs-over-overlayfs would see the
same lockdep warnings, right?

Thanks,
Miklos
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/