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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 707BECE79AE for ; Wed, 20 Sep 2023 07:37:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233776AbjITHho (ORCPT ); Wed, 20 Sep 2023 03:37:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48526 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233815AbjITHhS (ORCPT ); Wed, 20 Sep 2023 03:37:18 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 24058FB; Wed, 20 Sep 2023 00:37:02 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60753C433C7; Wed, 20 Sep 2023 07:37:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1695195421; bh=z1dy31UeAiNB72SwXICT2TJ42xSh8mt5/7TGfDru1x0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Y/66sa17bNa1qC8ThA1zSpgs9biCJH1Ajq5zq+89aqkyyGbjOYvXo/ix8Ipb4iCbJ prWNMZnrLsew+TlFTLIEqYJ0sVZkH3HvclRrEsMYJVRIV4pUKy2Uz0sOWBMOQZE2hj n9SC8mBlrHgeSegE0Ii4Sg9EwFJ1viOeEpJDATKEG7WHw94hPro747FW/4htGtWSO2 vXoQKlxD8oaN8exIdqpRKtQWTGUKpKr4c7O2XrYV42TXjlaPA1bzwi3KR2w6OMd9Ck G3YBFcWZxiFlIaJJdOQEavZpDwaPVRVojE1MmeCM/4Q2GkOLHauvubw5qiw/xQhm/h 1XyGgUohrjsfw== Date: Wed, 20 Sep 2023 00:36:59 -0700 From: Eric Biggers To: syzbot Cc: adilger.kernel@dilger.ca, krisman@collabora.com, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, tytso@mit.edu Subject: Re: [syzbot] [ext4?] general protection fault in utf8nlookup Message-ID: <20230920073659.GC2739@sol.localdomain> References: <0000000000001f0b970605c39a7e@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0000000000001f0b970605c39a7e@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 19, 2023 at 10:25:22PM -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: e42bebf6db29 Merge tag 'efi-fixes-for-v6.6-1' of git://git.. > git tree: upstream > console+strace: https://syzkaller.appspot.com/x/log.txt?x=179f4a38680000 > kernel config: https://syzkaller.appspot.com/x/.config?x=df91a3034fe3f122 > dashboard link: https://syzkaller.appspot.com/bug?extid=9cf75dc581fb4307d6dd > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1374a174680000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12b12928680000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/14a6a5d23944/disk-e42bebf6.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/98cc4c220388/vmlinux-e42bebf6.xz > kernel image: https://storage.googleapis.com/syzbot-assets/6a1d09cf21bf/bzImage-e42bebf6.xz > mounted in repro #1: https://storage.googleapis.com/syzbot-assets/37e5beb24789/mount_0.gz > mounted in repro #2: https://storage.googleapis.com/syzbot-assets/f219a9e665e9/mount_8.gz > > The issue was bisected to: > > commit b81427939590450172716093dafdda8ef52e020f > Author: Eric Biggers > Date: Mon Aug 14 18:29:02 2023 +0000 > > ext4: remove redundant checks of s_encoding > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10852352680000 > final oops: https://syzkaller.appspot.com/x/report.txt?x=12852352680000 > console output: https://syzkaller.appspot.com/x/log.txt?x=14852352680000 This report is expected for now, since the repro involves writing to the page cache of a mounted block device. For more information see https://lore.kernel.org/linux-fsdevel/20230813001202.GE41642@sol.localdomain and https://lore.kernel.org/linux-fsdevel/20230814182903.37267-2-ebiggers@kernel.org. Also https://lore.kernel.org/linux-fsdevel/20230704122727.17096-1-jack@suse.cz which will ultimately be the fix for this class of issue. Note: the repro that syzkaller generated for this is very strange (even moreso than usual for syzkaller repros...) because it replaces its "scratch space" at address 0x20000000 with a different mapping, specifically a mapping for a file that is mounted as a filesystem via loopback. That makes "syscalls" have weird side effects as a result of the repro writing parameters to the address that is supposed to contain its scratch space. I don't think this should be happening, so I've opened https://github.com/google/syzkaller/issues/4216 for it. - Eric