linux-kernel - Re: tty: AB-BA between tty->legacy_mutex and devpts

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]

Date:	Mon, 28 May 2012 20:50:02 +0100
From:	Alan Cox <alan@...ux.intel.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Jiri Slaby <jslaby@...e.cz>, linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: tty: AB-BA between tty->legacy_mutex and devpts_mutex

On Mon, 28 May 2012 21:02:15 +0200 (CEST)
Jiri Kosina <jkosina@...e.cz> wrote:

> On Mon, 28 May 2012, Jiri Kosina wrote:
> 
> > ======================================================
> > [ INFO: possible circular locking dependency detected ]
> > 3.4.0-08219-g238d69d #11 Not tainted
> > -------------------------------------------------------
> > blogd/265 is trying to acquire lock:
> >  (devpts_mutex){+.+.+.}, at: [<ffffffff8134d696>]
> > pty_close+0x166/0x190
> > 
> > but task is already holding lock:
> >  (&tty->legacy_mutex){+.+.+.}, at: [<ffffffff8150f632>]
> > tty_lock+0x22/0x29
> > 
> > which lock already depends on the new lock.
> 
> [ ... snip ... ]
> 
> > This deadlock scenario doesn't really seem realistic, as it's
> > between open()/close(). Not being really familiar with tty layer, I
> > am not sure what the proper lock ordering in this case is, I am
> > just reporting for you guys to decide how to get rid of this one.
> 
> This seems to have been caused by
> 
> commit d739e65bb21d34f0f5d3bf4048410e534fbec148
> Author: Alan Cox <alan@...ux.intel.com>
> Date:   Thu May 3 22:22:09 2012 +0100
> 
>     pty: Lock the devpts bits privately

Already fixed. It turned out we could just get rid of the lock there
anyway
--
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/