linux-kernel - Re: [linux-next / tty] possible circular locking dependency detected

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: <20170603093420.GB9120@kroah.com>
Date:   Sat, 3 Jun 2017 18:34:20 +0900
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Vegard Nossum <vegard.nossum@...cle.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Jiri Slaby <jslaby@...e.com>, linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [linux-next / tty] possible circular locking dependency detected

On Mon, May 29, 2017 at 12:43:39PM +0200, Vegard Nossum wrote:
> On 05/22/17 12:27, Vegard Nossum wrote:
> > On 05/22/17 12:24, Greg Kroah-Hartman wrote:
> > > On Mon, May 22, 2017 at 04:39:43PM +0900, Sergey Senozhatsky wrote:
> > > > Hello,
> > > > 
> > > > [ 1274.378287] ======================================================
> > > > [ 1274.378289] WARNING: possible circular locking dependency detected
> > > > [ 1274.378290]
> > > > 4.12.0-rc1-next-20170522-dbg-00007-gc09b2ab28b74-dirty #1317 Not
> > > > tainted
> > > > [ 1274.378291] ------------------------------------------------------
> > > > [ 1274.378293] kworker/u8:5/111 is trying to acquire lock:
> > > > [ 1274.378294]  (&buf->lock){+.+...}, at: [<ffffffff812f2831>]
> > > > tty_buffer_flush+0x34/0x88
> > > > [ 1274.378300]
> > > >                 but task is already holding lock:
> > > > [ 1274.378301]  (&o_tty->termios_rwsem/1){++++..}, at:
> > > > [<ffffffff812ee5c7>] isig+0x47/0xd2
> > > > [ 1274.378307]
> > > >                 which lock already depends on the new lock.
> > > > 
> > 
> > > Any hint as to what you were doing when this happened?
> > > 
> > > Does this also show up in 4.11?
> > 
> > It's my patch "tty: fix port buffer locking" :-/
> > 
> > At a glance, looks related to pty taking the lock on the other side in a
> > different order. I'll have a closer look.
> 
> I can reproduce the lockdep report locally on v4.12-rc3. Looking at it now.

Any ideas?  Or should I just revert the original patch?

thanks,

greg k-h