Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932068AbaA1Oxa (ORCPT ); Tue, 28 Jan 2014 09:53:30 -0500 Received: from cantor2.suse.de ([195.135.220.15]:59713 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754706AbaA1Ox3 (ORCPT ); Tue, 28 Jan 2014 09:53:29 -0500 Date: Tue, 28 Jan 2014 15:53:27 +0100 From: Jan Kara To: Jiri Kosina Cc: Jan Kara , Dave Jones , Linus Torvalds , Linux Kernel Subject: Re: fanotify use after free. Message-ID: <20140128145327.GC13676@quack.suse.cz> References: <20140123150540.GD28796@quack.suse.cz> <20140123235549.GA7363@quack.suse.cz> <20140127234017.GA7868@quack.suse.cz> <20140128061037.GA27636@redhat.com> <20140128080201.GA13676@quack.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 28-01-14 12:07:51, Jiri Kosina wrote: > On Tue, 28 Jan 2014, Jan Kara wrote: > > > > 2b:* 4d 8b 64 c6 08 mov 0x8(%r14,%rax,8),%r12 <-- trapping instruction > > > > > > R14 is 0x6b6b6b6b6b6b6c03, which looks like a use-after-free. > > Yup. But I'm somewhat puzzled by the trace. We crash when calling > > fsnotify_destroy_event() from fanotify_handle_event(). The fsnotify code > > has been called from do_sys_open() so the event was a 'FS_OPEN' which fails > > the fsn_event->mask & FAN_ALL_PERM_EVENTS test. > > > > Slapping my forehead, that's a really stupid bug. The event > > fsnotify_add_notify_event() returns may be freed by the time we return > > because we already dropped the notification mutex. And then fsn_event->mask > > & FAN_ALL_PERM_EVENTS test will pass because FAN_ALL_PERM_EVENTS matches > > with the poison pattern 0x6b6b6b6b. So yet another hacked up version of > > fanotify fix is attached. And I have to seriously think about use counts > > for fanotify version of that struct. > > With the fixed version of the patch, all the fanotify-related oopses are > gone on my system. Thanks for testing. So now I have to come up with something mergeable :) Honza -- Jan Kara SUSE Labs, CR -- 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/