From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758364AbZIOTcE (ORCPT ); Tue, 15 Sep 2009 15:32:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758273AbZIOTcC (ORCPT ); Tue, 15 Sep 2009 15:32:02 -0400 Received: from brick.kernel.dk ([93.163.65.50]:59106 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753035AbZIOTcB (ORCPT ); Tue, 15 Sep 2009 15:32:01 -0400 Date: Tue, 15 Sep 2009 21:32:04 +0200 From: Jens Axboe To: npiggin@suse.de Cc: Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [patch 3/5] fs: fix bdi writeback use after free 1 Message-ID: <20090915193204.GU23126@kernel.dk> References: <20090915191903.290006007@suse.de> <20090915192242.897829798@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090915192242.897829798@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 16 2009, npiggin@suse.de wrote: > By the time bdi_work_on_stack gets evaluated again in bdi_work_free, it > cna already have been deallocated and used for something else in the > !on stack case, giving a false positive in this test and causing corruption. You are right, that is also buggy... Applied. > > Signed-off-by: Nick Piggin > --- > fs/fs-writeback.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > Index: linux-2.6/fs/fs-writeback.c > =================================================================== > --- linux-2.6.orig/fs/fs-writeback.c > +++ linux-2.6/fs/fs-writeback.c > @@ -114,6 +114,7 @@ static void bdi_work_free(struct rcu_hea > static void wb_work_complete(struct bdi_work *work) > { > const enum writeback_sync_modes sync_mode = work->sync_mode; > + int onstack = bdi_work_on_stack(work); > > /* > * For allocated work, we can clear the done/seen bit right here. > @@ -121,9 +122,9 @@ static void wb_work_complete(struct bdi_ > * to after the RCU grace period, since the stack could be invalidated > * as soon as bdi_work_clear() has done the wakeup. > */ > - if (!bdi_work_on_stack(work)) > + if (!onstack) > bdi_work_clear(work); > - if (sync_mode == WB_SYNC_NONE || bdi_work_on_stack(work)) > + if (sync_mode == WB_SYNC_NONE || onstack) > call_rcu(&work->rcu_head, bdi_work_free); > } > > > -- Jens Axboe