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 66C10C2FC3C for ; Thu, 17 Aug 2023 14:22:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351329AbjHQOV5 (ORCPT ); Thu, 17 Aug 2023 10:21:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59612 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351831AbjHQOVh (ORCPT ); Thu, 17 Aug 2023 10:21:37 -0400 Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 78B3630E6 for ; Thu, 17 Aug 2023 07:21:34 -0700 (PDT) Received: from cwcc.thunk.org (pool-173-48-102-95.bstnma.fios.verizon.net [173.48.102.95]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 37HEL3Gn028243 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 17 Aug 2023 10:21:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mit.edu; s=outgoing; t=1692282065; bh=1nwFHxgw3tfo1n5h9l6XazSvo2VPtHFHrvBdlf/+dik=; h=Date:From:Subject:Message-ID:MIME-Version:Content-Type; b=AcXY8Cbxpc45eSuMMXguUD/M9Q8pRHIdlunOILVzRi6Mu0lxVfwMvbOGNYLImlHWa mol8ZLM5ejT3qFiXE6Q4avFUYwvDAm8JxL4yVXYWK7UisulDQJOERhkB5MjbuMcrGn ke2Pqcz7RRsgeggvxB0YAPlKXWzveqyGFMYJ7WieIACPzlbmC7zq/cqFnMkFQ9Kc+B ZwO1VOFEClnOOiGoirlgTq8uskoV1t+BlFJhbG1/cpU+8GwoYH/f5aXYZ7eqloYU4z E+oEh1lN6QU/ede4Qam73R6Zltdydy4skp2EM7YGc1khET3oncbKOilybqwBDd7+DV lg60TDoY9p4/A== Received: by cwcc.thunk.org (Postfix, from userid 15806) id 300A515C0501; Thu, 17 Aug 2023 10:21:03 -0400 (EDT) Date: Thu, 17 Aug 2023 10:21:03 -0400 From: "Theodore Ts'o" To: syzbot Cc: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, nathan@kernel.org, ndesaulniers@google.com, syzkaller-bugs@googlegroups.com, trix@redhat.com Subject: Re: [syzbot] [ext4?] kernel panic: EXT4-fs (device loop0): panic forced after error (3) Message-ID: <20230817142103.GA2247938@mit.edu> References: <000000000000530e0d060312199e@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <000000000000530e0d060312199e@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Aug 16, 2023 at 03:48:49PM -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: ae545c3283dc Merge tag 'gpio-fixes-for-v6.5-rc6' of git://.. > git tree: upstream > console+strace: https://syzkaller.appspot.com/x/log.txt?x=13e5d553a80000 > kernel config: https://syzkaller.appspot.com/x/.config?x=171b698bc2e613cf > dashboard link: https://syzkaller.appspot.com/bug?extid=27eece6916b914a49ce7 > 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=13433207a80000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=109cd837a80000 > > EXT4-fs error (device loop0): ext4_validate_block_bitmap:430: comm syz-executor211: bg 0: block 46: invalid block bitmap > Kernel panic - not syncing: EXT4-fs (device loop0): panic forced after error #syz invalid This is fundamentally a syzbot bug. The file system is horrifically corrupted, *and* the superblock has the "panic on error" (aka "panic onfile system corruption") bit set. This can be desireable because in a failover situation, if the file system is found to be corrupted, you *want* the primary server to fail, and let the secondary server to take over. This is a technique which is decades old. So this is Working As Intended, and is a classic example of (a) if you are root, you can force the file system to crash, and (b) a classic example of syzbot noise. (Five minutes of my life that I'm never getting back. :-) - Ted