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 E0F2AC77B60 for ; Sun, 23 Apr 2023 14:00:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230070AbjDWOAY (ORCPT ); Sun, 23 Apr 2023 10:00:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57086 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229663AbjDWOAV (ORCPT ); Sun, 23 Apr 2023 10:00:21 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F3C41FE3 for ; Sun, 23 Apr 2023 07:00:19 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 282EB61A27 for ; Sun, 23 Apr 2023 14:00:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1BE32C433D2; Sun, 23 Apr 2023 14:00:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1682258418; bh=rXa7qPtIZGglVvOdvfEFs+lsgsASMTAj/fjqzEcamoo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=0HBxJ96/rK7xfxinCXBvRC2dnxYjJbPapAoW/d0H5TAn22BFZCOUx2qcQhspeJ3BX HvW1yXodryz/7ob9AmU91FrPsC9aY3al0N3kQAL+hLgCC1mO8yNSUYBC75TmUUE2kG 8Of4sljZePqney0NhN7AmkToZqb11f4oAMhtlrqw= Date: Sun, 23 Apr 2023 16:00:15 +0200 From: Greg Kroah-Hartman To: Tetsuo Handa Cc: Dmitry Vyukov , syzbot , Jiri Slaby , linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [kernel?] KCSAN: data-race in __fput / __tty_hangup (4) Message-ID: <2023042342-nebula-hydrogen-baf4@gregkh> References: <00000000000013aaac05f9d44e7a@google.com> <6bec279c-07b3-d6f1-0860-4d6b136a2025@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6bec279c-07b3-d6f1-0860-4d6b136a2025@I-love.SAKURA.ne.jp> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 23, 2023 at 10:28:58PM +0900, Tetsuo Handa wrote: > On 2023/04/21 17:21, Dmitry Vyukov wrote: > > On Fri, 21 Apr 2023 at 10:18, syzbot > > wrote: > >> > >> Hello, > >> > >> syzbot found the following issue on: > >> > >> HEAD commit: fcd476ea6a88 Merge tag 'urgent-rcu.2023.03.28a' of git://g.. > >> git tree: upstream > >> console output: https://syzkaller.appspot.com/x/log.txt?x=146618b9c80000 > >> kernel config: https://syzkaller.appspot.com/x/.config?x=f7350c77b8056a38 > >> dashboard link: https://syzkaller.appspot.com/bug?extid=b7c3ba8cdc2f6cf83c21 > >> compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2 > >> > >> Unfortunately, I don't have any reproducer for this issue yet. > >> > >> Downloadable assets: > >> disk image: https://storage.googleapis.com/syzbot-assets/f3d8ce4faab0/disk-fcd476ea.raw.xz > >> vmlinux: https://storage.googleapis.com/syzbot-assets/fc53d9dee279/vmlinux-fcd476ea.xz > >> kernel image: https://storage.googleapis.com/syzbot-assets/22ad755d39b2/bzImage-fcd476ea.xz > >> > >> IMPORTANT: if you fix the issue, please add the following tag to the commit: > >> Reported-by: syzbot+b7c3ba8cdc2f6cf83c21@syzkaller.appspotmail.com > > > > If I am reading this correctly, this race can lead to NULL derefs > > among other things. > > hung_up_tty_fops does not have splice_read, while other fops have. > > > > So the following code in splice can execute NULL callback: > > > > if (unlikely(!in->f_op->splice_read)) > > return warn_unsupported(in, "read"); > > return in->f_op->splice_read(in, ppos, pipe, len, flags); > > Hmm, it seems to me that we need multiple patches (which would become too big to > backport) for fixing this bug. Fix the bug properly first. And then only start to worry about stable kernels, don't let the existance of them affect your development efforts at all please. thanks, greg k-h