From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from m12-17.163.com ([220.181.12.17]:43797 "EHLO m12-17.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726176AbeKZVaO (ORCPT ); Mon, 26 Nov 2018 16:30:14 -0500 Date: Mon, 26 Nov 2018 18:36:19 +0800 From: PanBian Subject: Re: [PATCH] xfs: libxfs: move xfs_perag_put late Message-ID: <20181126103619.GA95394@bp> Reply-To: PanBian References: <1543052660-58625-1-git-send-email-bianpan2016@163.com> <20181126093139.cgojlmtubzuzdb23@hades.usersys.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181126093139.cgojlmtubzuzdb23@hades.usersys.redhat.com> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Carlos Maiolino Cc: "Darrick J. Wong" , linux-xfs@vger.kernel.org, Brian Foster , Dave Chinner , linux-kernel@vger.kernel.org On Mon, Nov 26, 2018 at 10:31:39AM +0100, Carlos Maiolino wrote: > On Sat, Nov 24, 2018 at 05:44:20PM +0800, Pan Bian wrote: > > The function xfs_alloc_get_freelist calls xfs_perag_put to drop the > > reference. In this case, pag may be released. However, > > pag->pagf_btreeblks is read and write after the put operation. This may > > result in a use-after-free bug. This patch moves the put operation late. > > > > The patch looks reasonable, can you detail more how did you find it? Via code > inspection of you hit this user-after-free in some way? I wrote a tool to check such bugs statically. It first scans the source code to extract paired alloc/free functions. Equipped with such functions, it performs an intra-procedural data flow analysis to detect mismatched alloc/free bugs and use-after-free bugs. Best regards, Pan Bian