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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 40B08C49360 for ; Sat, 12 Jun 2021 14:36:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C90A613AA for ; Sat, 12 Jun 2021 14:36:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231342AbhFLOiT (ORCPT ); Sat, 12 Jun 2021 10:38:19 -0400 Received: from cloud48395.mywhc.ca ([173.209.37.211]:55432 "EHLO cloud48395.mywhc.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230191AbhFLOiS (ORCPT ); Sat, 12 Jun 2021 10:38:18 -0400 Received: from modemcable064.203-130-66.mc.videotron.ca ([66.130.203.64]:41668 helo=[192.168.1.179]) by cloud48395.mywhc.ca with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1ls4kC-0001KT-UU; Sat, 12 Jun 2021 10:36:16 -0400 Message-ID: <9628ac27c07db760415d382e26b5a0ced41f5851.camel@trillion01.com> Subject: Re: [PATCH] coredump: Limit what can interrupt coredumps From: Olivier Langlois To: "Eric W. Biederman" , Linus Torvalds Cc: Linux Kernel Mailing List , linux-fsdevel , io-uring , Alexander Viro , Jens Axboe , "Pavel Begunkov>" , Oleg Nesterov Date: Sat, 12 Jun 2021 10:36:15 -0400 In-Reply-To: <87sg1p4h0g.fsf_-_@disp2133> References: <192c9697e379bf084636a8213108be6c3b948d0b.camel@trillion01.com> <9692dbb420eef43a9775f425cb8f6f33c9ba2db9.camel@trillion01.com> <87h7i694ij.fsf_-_@disp2133> <198e912402486f66214146d4eabad8cb3f010a8e.camel@trillion01.com> <87eeda7nqe.fsf@disp2133> <87pmwt6biw.fsf@disp2133> <87czst5yxh.fsf_-_@disp2133> <87y2bh4jg5.fsf@disp2133> <87sg1p4h0g.fsf_-_@disp2133> Organization: Trillion01 Inc Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.40.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - cloud48395.mywhc.ca X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - trillion01.com X-Get-Message-Sender-Via: cloud48395.mywhc.ca: authenticated_id: olivier@trillion01.com X-Authenticated-Sender: cloud48395.mywhc.ca: olivier@trillion01.com X-Source: X-Source-Args: X-Source-Dir: Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Thu, 2021-06-10 at 15:11 -0500, Eric W. Biederman wrote: > > Olivier Langlois has been struggling with coredumps being incompletely > written in > processes using io_uring. > > Olivier Langlois writes: > > io_uring is a big user of task_work and any event that io_uring made > > a > > task waiting for that occurs during the core dump generation will > > generate a TIF_NOTIFY_SIGNAL. > > > > Here are the detailed steps of the problem: > > 1. io_uring calls vfs_poll() to install a task to a file wait queue > >    with io_async_wake() as the wakeup function cb from > > io_arm_poll_handler() > > 2. wakeup function ends up calling task_work_add() with TWA_SIGNAL > > 3. task_work_add() sets the TIF_NOTIFY_SIGNAL bit by calling > >    set_notify_signal() > > The coredump code deliberately supports being interrupted by SIGKILL, > and depends upon prepare_signal to filter out all other signals.   Now > that signal_pending includes wake ups for TIF_NOTIFY_SIGNAL this hack > in dump_emitted by the coredump code no longer works. > > Make the coredump code more robust by explicitly testing for all of > the wakeup conditions the coredump code supports.  This prevents > new wakeup conditions from breaking the coredump code, as well > as fixing the current issue. > > The filesystem code that the coredump code uses already limits > itself to only aborting on fatal_signal_pending.  So it should > not develop surprising wake-up reasons either. > > v2: Don't remove the now unnecessary code in prepare_signal. > > Cc: stable@vger.kernel.org > Fixes: 12db8b690010 ("entry: Add support for TIF_NOTIFY_SIGNAL") > Reported-by: Olivier Langlois > Signed-off-by: "Eric W. Biederman" > --- >  fs/coredump.c | 2 +- >  1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/coredump.c b/fs/coredump.c > index 2868e3e171ae..c3d8fc14b993 100644 > --- a/fs/coredump.c > +++ b/fs/coredump.c > @@ -519,7 +519,7 @@ static bool dump_interrupted(void) >          * but then we need to teach dump_write() to restart and clear >          * TIF_SIGPENDING. >          */ > -       return signal_pending(current); > +       return fatal_signal_pending(current) || freezing(current); >  } >   >  static void wait_for_dump_helpers(struct file *file) Tested-by: Olivier Langlois