From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87CE7C432C0 for ; Sun, 1 Dec 2019 00:05:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 58D6E2086A for ; Sun, 1 Dec 2019 00:05:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727011AbfLAAEy (ORCPT ); Sat, 30 Nov 2019 19:04:54 -0500 Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:36306 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725897AbfLAAEy (ORCPT ); Sat, 30 Nov 2019 19:04:54 -0500 Received: from dimstar.local.net (n122-110-44-45.sun2.vic.optusnet.com.au [122.110.44.45]) by mail104.syd.optusnet.com.au (Postfix) with SMTP id 964D743FE5E for ; Sun, 1 Dec 2019 11:04:40 +1100 (AEDT) Received: (qmail 19400 invoked by uid 501); 1 Dec 2019 00:04:39 -0000 Date: Sun, 1 Dec 2019 11:04:39 +1100 From: Duncan Roe To: Dmitry Vyukov Cc: Al Viro , Chris Metcalf , coreteam@netfilter.org, David Miller , Chen Gang , Patrick McHardy , Jozsef Kadlecsik , linux-fsdevel , LKML , netdev , NetFilter , Pablo Neira Ayuso , syzkaller-bugs Subject: Re: KASAN: use-after-free Read in blkdev_get Message-ID: <20191201000439.GA15496@dimstar.local.net> Mail-Followup-To: Dmitry Vyukov , Al Viro , Chris Metcalf , coreteam@netfilter.org, David Miller , Chen Gang , Patrick McHardy , Jozsef Kadlecsik , linux-fsdevel , LKML , netdev , NetFilter , Pablo Neira Ayuso , syzkaller-bugs References: <000000000000e59aab056e8873ae@google.com> <0000000000000beff305981c5ac6@google.com> <20191124193035.GA4203@ZenIV.linux.org.uk> <20191130110645.GA4405@dimstar.local.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=LYdCFQXi c=1 sm=1 tr=0 a=4DzML1vCOQ6Odsy8BUtSXQ==:117 a=4DzML1vCOQ6Odsy8BUtSXQ==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=pxVhFHJ0LMsA:10 a=RSmzAf-M6YYA:10 a=PO7r1zJSAAAA:8 a=7QvuB2UPAAAA:8 a=edf1wS77AAAA:8 a=hSkVLCK3AAAA:8 a=mzoz-TVAAAAA:20 a=VwQbUJbxAAAA:8 a=kGbAZRCgAAAA:20 a=EI3vZeS8J00HEDANUmYA:9 a=CjuIK1q_8ugA:10 a=vVHabExCe68A:10 a=PyAPxfarwdVEPLbpdMBu:22 a=DcSpbTIhAlouE1Uv7lRv:22 a=cQPPKAXgyycSBL8etih5:22 a=AjGcO6oz07-iQ99wixmX:22 a=pHzHmUro8NiASowvMSCR:22 a=Ew2E2A-JSTLzCXPT_086:22 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, Nov 30, 2019 at 04:53:12PM +0100, Dmitry Vyukov wrote: > On Sat, Nov 30, 2019 at 12:06 PM Duncan Roe wrote: > > > > syzbot has bisected this bug to: > > > > > > > > commit 77ef8f5177599efd0cedeb52c1950c1bd73fa5e3 > > > > Author: Chris Metcalf > > > > Date: Mon Jan 25 20:05:34 2016 +0000 > > > > > > > > tile kgdb: fix bug in copy to gdb regs, and optimize memset > > > > > > > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1131bc0ee00000 > > > > start commit: f5b7769e Revert "debugfs: inode: debugfs_create_dir uses m.. > > > > git tree: upstream > > > > final crash: https://syzkaller.appspot.com/x/report.txt?x=1331bc0ee00000 > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1531bc0ee00000 > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=709f8187af941e84 > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=eaeb616d85c9a0afec7d > > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=177f898f800000 > > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=147eb85f800000 > > > > > > > > Reported-by: syzbot+eaeb616d85c9a0afec7d@syzkaller.appspotmail.com > > > > Fixes: 77ef8f517759 ("tile kgdb: fix bug in copy to gdb regs, and optimize > > > > memset") > > > > > > > > For information about bisection process see: https://goo.gl/tpsmEJ#bisection > > > > > > Seriously? How can the commit in question (limited to arch/tile/kernel/kgdb.c) > > > possibly affect a bug that manages to produce a crash report with > > > RSP: 0018:ffffffff82e03eb8 EFLAGS: 00000282 > > > RAX: 0000000000000000 RBX: ffffffff82e00000 RCX: 0000000000000000 > > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff81088779 > > > RBP: ffffffff82e03eb8 R08: 0000000000000000 R09: 0000000000000001 > > > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > > > R13: 0000000000000000 R14: 0000000000000000 R15: ffffffff82e00000 > > > FS: 0000000000000000(0000) GS:ffff88021fc00000(0000) knlGS:0000000000000000 > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > CR2: 000000c420447ff8 CR3: 0000000213184000 CR4: 00000000001406f0 > > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > > in it? Unless something very odd has happened to tile, this crash has > > > been observed on 64bit x86; the names of registers alone are enough > > > to be certain of that. > > > > > > And the binaries produced by an x86 build should not be affected by any > > > changes in arch/tile; not unless something is very wrong with the build > > > system. It's not even that this commit has fixed an earlier bug that > > > used to mask the one manifested here - it really should have had zero > > > impact on x86 builds, period. > > > > > > So I'm sorry, but I'm calling bullshit. Something's quite wrong with > > > the bot - either its build system or the bisection process. > > > > The acid test would be: does reverting that commit make the problem go away? > > > > See, for example, https://bugzilla.kernel.org/show_bug.cgi?id=203935 > > > > Cheers ... Duncan. > > This is done as part of any bisection by definition, right? The test > was done on the previous commit (effectively this one reverted) and no > crash was observed. Otherwise bisection would have been pointed to a > different commit. > Agree that's what bisecting does. What I had in mind was to make a patch to remove the identified commit, and apply that to the most recent revision possible. Then see if that makes the problem go away. However when I look at my clone of git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git and compare 77ef8f5177 with the previous commit a7d1357664, "git diff --stat" shows > 745 files changed, 8192 insertions(+), 15408 deletions(-) The last few lines from a grep of "arch" are: > arch/s390/oprofile/backtrace.c | 8 +- > arch/tile/kernel/kgdb.c | 8 +- > arch/x86/Kconfig | 5 +- > arch/x86/include/asm/livepatch.h | 2 +- > arch/x86/include/asm/processor.h | 2 +- > arch/x86/kernel/cpu/perf_event_amd_uncore.c | 2 + > arch/x86/lib/copy_user_64.S | 142 ++- > arch/x86/mm/fault.c | 15 +- > arch/x86/mm/gup.c | 2 +- > arch/x86/mm/numa.c | 2 +- Enough said? Cheers ... Duncan.