Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758396Ab2FAU7z (ORCPT ); Fri, 1 Jun 2012 16:59:55 -0400 Received: from mail-wg0-f42.google.com ([74.125.82.42]:60347 "EHLO mail-wg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753667Ab2FAU7y (ORCPT ); Fri, 1 Jun 2012 16:59:54 -0400 Subject: Re: [PATCH] tty: add lockdep annotations From: Eric Dumazet To: Alan Cox Cc: Linus Torvalds , Alan Cox , "linux-kernel@vger.kernel.org" , Jens Axboe In-Reply-To: <20120601215620.305155c0@pyramind.ukuu.org.uk> References: <4FC6189B.9080909@fusionio.com> <1338402812.2760.413.camel@edumazet-glaptop> <4FC66D3D.6080509@fusionio.com> <1338404902.2760.451.camel@edumazet-glaptop> <1338410107.2760.544.camel@edumazet-glaptop> <1338456918.2760.1318.camel@edumazet-glaptop> <1338574627.2760.1545.camel@edumazet-glaptop> <1338583498.2760.1648.camel@edumazet-glaptop> <20120601215620.305155c0@pyramind.ukuu.org.uk> Content-Type: text/plain; charset="UTF-8" Date: Fri, 01 Jun 2012 22:59:49 +0200 Message-ID: <1338584389.2760.1653.camel@edumazet-glaptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 937 Lines: 29 On Fri, 2012-06-01 at 21:56 +0100, Alan Cox wrote: > > Yes, tty->driver deref is ok (tty points to valid memory), but crash is > > on tty->driver->ops (driver points to freed/illegal memory) > > > > using slub_debug=FZPU, I can indeed see RDI=6b6b6b6b6b6b6b6b > > driver and driver->ops is basically const and it's not what you'd expect > from a tty refcount bug. The driver side puts shouldn't have changed but > I'll take a look over that patch and the error paths closely again just > in case. right The code looks like : ... call mcount mov %rdi,%rbx mov 0x10(%rdi),%rdi tty->driver <> mov 0xf8(%rdi),%rax CRASH So tty was freed an tty->driver contains 6b6b6b6b6b6b6b6b -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/