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=-8.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=ham 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 21D79C04AB4 for ; Fri, 17 May 2019 14:08:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E44092082E for ; Fri, 17 May 2019 14:08:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="bCbydxhI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729041AbfEQOIu (ORCPT ); Fri, 17 May 2019 10:08:50 -0400 Received: from mail-it1-f195.google.com ([209.85.166.195]:39151 "EHLO mail-it1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728260AbfEQOIt (ORCPT ); Fri, 17 May 2019 10:08:49 -0400 Received: by mail-it1-f195.google.com with SMTP id 9so12175170itf.4 for ; Fri, 17 May 2019 07:08:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=wnE5ugQSV+EX8NJq3bXAxc5+808EKDRQWDkjcFDm76g=; b=bCbydxhIRSNOt3TwDd4BdgsvwmO+IYfUOtPAEAjE2b/cMzWleRTqkn3UbY13DGYF1K x4yKjJrT6J8shR6+H2q3zQgZGYdC9a0WvJmPeCQ4S0ffoyFISZ2B0V76p9gorMUSQ6ER bRKXGBesi4Znrw/l7X+0AcOZOXjCjR7CaV4xUbio+/j3wXC0fnhOlLLnTQyxz5/dsx5U oSqt/pSv99S0Oftm7Z+LRef9zrwxu9hleDGUMXzjoDfyHveXTeVIn3F3wfTR3OL6TJGu 082bIphpUtJ9LlQ5xRROlabqAeWGtZVRZrntcO9m/4dBEXkJ5cyyPS6SNomLQs8wNpZ8 Xw9Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=wnE5ugQSV+EX8NJq3bXAxc5+808EKDRQWDkjcFDm76g=; b=EDas/L8YMVgiXAA+Fni5SzK1rhns0bTSY3fp33bUBi/lskJUDsCe0XOX8jakwKvA7k zMrECTz54eQDbjYh8n+A+4ztzZollNCa92q4J+/Fv70klbeyVbxFsJh/j7OY6JPiuX42 0/9unRklfhCx9f+3XjyE6lDLRp/qrxUCxLuNJyTUbZsqxzWiCRFDWa0vHS2wHOQkw/sh IbkDh/jxOyp2CC/d5tOCAw0N/t8bvi0lidPeAyUpBCP2ID4unKNxb98HXwpuOOB0FUiY DXREfqIDnzERNupdxtWNO/bG4XNtIBJBaW4XjeZN4ZDfy4A+aJOLYgg+d5uXJ0xwmVwQ 4ssQ== X-Gm-Message-State: APjAAAUwXDa9mWBs+j3Nhg4lj+MScMXsluRS3msuWFF+YqkGXDFCfOg+ y6wk5dbR7rdvvVi3levI7k3T9+vBMPswUend2SXe0w== X-Google-Smtp-Source: APXvYqzuUfMi8lV0T0lwvRZljXNCxDfrTqM5N220cNATHJKTOwPJxnkJlmO1e5pjoYWFu4RheZnomcXVJ0T1qE6Tsfg= X-Received: by 2002:a02:412:: with SMTP id 18mr1390107jab.82.1558102128480; Fri, 17 May 2019 07:08:48 -0700 (PDT) MIME-Version: 1.0 References: <00000000000014285d05765bf72a@google.com> <0000000000000eaf23058912af14@google.com> <20190517134850.GG17978@ZenIV.linux.org.uk> In-Reply-To: <20190517134850.GG17978@ZenIV.linux.org.uk> From: Dmitry Vyukov Date: Fri, 17 May 2019 16:08:35 +0200 Message-ID: Subject: Re: BUG: unable to handle kernel paging request in do_mount To: Al Viro Cc: syzbot , linux-fsdevel , LKML , sabin.rapan@gmail.com, syzkaller-bugs Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 17, 2019 at 3:48 PM Al Viro wrote: > > On Fri, May 17, 2019 at 03:17:02AM -0700, syzbot wrote: > > This bug is marked as fixed by commit: > > vfs: namespace: error pointer dereference in do_remount() > > But I can't find it in any tested tree for more than 90 days. > > Is it a correct commit? Please update it by replying: > > #syz fix: exact-commit-title > > Until then the bug is still considered open and > > new crashes with the same signature are ignored. > > Could somebody explain how the following situation is supposed to > be handled: > > 1) branch B1 with commits C1, C2, C3, C4 is pushed out > 2) C2 turns out to have a bug, which gets caught and fixed > 3) fix is folded in and branch B2 with C1, C2', C3', C4' is > pushed out. The bug is not in it anymore. > 4) B1 is left mouldering (or is entirely removed); B2 is > eventually merged into other trees. > > This is normal and it appears to be problematic for syzbot. > How to deal with that? One thing I will *NOT* do in such > situations is giving up on folding the fixes in. Bisection > hazards alone make that a bad idea. linux-next creates a bit of a havoc. The ideal way of handling this is including Tested-by: tag into C2'. Reported-by: would work too, but people suggested that Reported-by: is confusing in this situation because it suggests that the commit fixes a bug in some previous commit. Technically, syzbot now accepts any tag, so With-inputs-from: syzbot+73c7fe4f77776505299b@syzkaller.appspotmail.com would work too. At this point we obvious can't fix up C2'. For such cases syzbot accepts #syz fix command to associate bugs with fixes. So replying with "#syz fix: C2'-commit-title" should do.