Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965727AbdLSJEc (ORCPT ); Tue, 19 Dec 2017 04:04:32 -0500 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:54585 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935353AbdLSJEW (ORCPT ); Tue, 19 Dec 2017 04:04:22 -0500 X-ME-Sender: Date: Tue, 19 Dec 2017 20:04:18 +1100 From: "Tobin C. Harding" To: Dmitry Vyukov Cc: Kees Cook , Tetsuo Handa , Linux-MM , syzbot , David Windsor , keun-o.park@darkmatter.ae, Laura Abbott , LKML , Mark Rutland , Ingo Molnar , syzkaller-bugs@googlegroups.com, Will Deacon Subject: Re: BUG: bad usercopy in memdup_user Message-ID: <20171219090418.GS19604@eros> References: <001a113e9ca8a3affd05609d7ccf@google.com> <6a50d160-56d0-29f9-cfed-6c9202140b43@I-love.SAKURA.ne.jp> <20171219083746.GR19604@eros> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Mailer: Mutt 1.5.24 (2015-08-30) User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1440 Lines: 37 On Tue, Dec 19, 2017 at 09:41:39AM +0100, Dmitry Vyukov wrote: > On Tue, Dec 19, 2017 at 9:37 AM, Tobin C. Harding wrote: > >> > wrote: > >> >> On 2017/12/18 22:40, syzbot wrote: > >> >>> Hello, > >> >>> > >> >>> syzkaller hit the following crash on 6084b576dca2e898f5c101baef151f7bfdbb606d > >> >>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master > >> >>> compiler: gcc (GCC) 7.1.1 20170620 > >> >>> .config is attached > >> >>> Raw console output is attached. > >> >>> > >> >>> Unfortunately, I don't have any reproducer for this bug yet. > >> >>> > >> >>> > >> >> > >> >> This BUG is reporting > >> >> > >> >> [ 26.089789] usercopy: kernel memory overwrite attempt detected to 0000000022a5b430 (kmalloc-1024) (1024 bytes) > >> >> > >> >> line. But isn't 0000000022a5b430 strange for kmalloc(1024, GFP_KERNEL)ed kernel address? > >> > > >> > The address is hashed (see the %p threads for 4.15). > >> > >> > >> +Tobin, is there a way to disable hashing entirely? The only > >> designation of syzbot is providing crash reports to kernel developers > >> with as much info as possible. It's fine for it to leak whatever. > > > > We have new specifier %px to print addresses in hex if leaking info is > > not a worry. > > This is not a per-printf-site thing. It's per-machine thing. There is no way to disable the hashing currently built into the system. Tobin