From mboxrd@z Thu Jan 1 00:00:00 1970 From: PanBian Subject: Re: [PATCH] f2fs: read page index before freeing Date: Tue, 27 Nov 2018 08:22:47 +0800 Message-ID: <20181127002247.GA109273@bp> References: <1542884326-74903-1-git-send-email-bianpan2016@163.com> <3ebe6814-586e-77e8-52fa-47fb61d760f5@huawei.com> <20181126102841.GA94853@bp> Reply-To: PanBian Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Chao Yu Cc: Jaegeuk Kim , linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org List-Id: linux-f2fs-devel.lists.sourceforge.net On Mon, Nov 26, 2018 at 07:07:08PM +0800, Chao Yu wrote: > On 2018/11/26 18:28, PanBian wrote: > > On Mon, Nov 26, 2018 at 05:13:53PM +0800, Chao Yu wrote: > >> Hi Pan, > >> > >> On 2018/11/22 18:58, Pan Bian wrote: > >>> The function truncate_node frees the page with f2fs_put_page. However, > >>> the page index is read after that. So, the patch reads the index before > >>> freeing the page. > >> > >> I notice that you found another use-after-free bug in ext4, out of > >> curiosity, I'd like to ask how do you find those bugs? by tool or code review? > > > > I found such bugs by the aid of a tool I wrote recently. I designed a method > > to automatically find paired alloc/free functions. With such functions, I > > wrote two checkers, one to check mismatched alloc/free bugs, the other to > > check use-after-free and double-free bugs. > > Excellent! Do you have any plan to open its source or announce it w/ binary > to linux kernel developers, I think w/ it we can help to improve kernel's > code quality efficiently. Yes. I am now writing a paper about the method. I will open the source code as soon as I complete the paper and some optimizations. Best, Pan