From patchwork Wed Jul 20 16:51:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 12924318 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 7092EC43334 for ; Wed, 20 Jul 2022 16:51:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234923AbiGTQvr (ORCPT ); Wed, 20 Jul 2022 12:51:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50810 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235002AbiGTQvj (ORCPT ); Wed, 20 Jul 2022 12:51:39 -0400 Received: from out02.mta.xmission.com (out02.mta.xmission.com [166.70.13.232]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D598D675BB; Wed, 20 Jul 2022 09:51:35 -0700 (PDT) Received: from in02.mta.xmission.com ([166.70.13.52]:54210) by out02.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1oECv8-00AUeC-Tm; Wed, 20 Jul 2022 10:51:34 -0600 Received: from ip68-227-174-4.om.om.cox.net ([68.227.174.4]:40140 helo=email.froward.int.ebiederm.org.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1oECv7-002zG9-U8; Wed, 20 Jul 2022 10:51:34 -0600 From: "Eric W. Biederman" To: Jens Axboe Cc: Olivier Langlois , Pavel Begunkov , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, Alexander Viro , Oleg Nesterov , Linus Torvalds References: <192c9697e379bf084636a8213108be6c3b948d0b.camel@trillion01.com> <9692dbb420eef43a9775f425cb8f6f33c9ba2db9.camel@trillion01.com> <87h7i694ij.fsf_-_@disp2133> <1b519092-2ebf-3800-306d-c354c24a9ad1@gmail.com> <13250a8d-1a59-4b7b-92e4-1231d73cbdda@gmail.com> <878rw9u6fb.fsf@email.froward.int.ebiederm.org> <303f7772-eb31-5beb-2bd0-4278566591b0@gmail.com> <87ilsg13yz.fsf@email.froward.int.ebiederm.org> <8218f1a245d054c940e25142fd00a5f17238d078.camel@trillion01.com> <87y1wnrap0.fsf_-_@email.froward.int.ebiederm.org> Date: Wed, 20 Jul 2022 11:51:27 -0500 In-Reply-To: <87y1wnrap0.fsf_-_@email.froward.int.ebiederm.org> (Eric W. Biederman's message of "Wed, 20 Jul 2022 11:49:31 -0500") Message-ID: <87mtd3rals.fsf_-_@email.froward.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-XM-SPF: eid=1oECv7-002zG9-U8;;;mid=<87mtd3rals.fsf_-_@email.froward.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.174.4;;;frm=ebiederm@xmission.com;;;spf=softfail X-XM-AID: U2FsdGVkX1+oGLq5krvvMrRh4NiQGwHlLaqBKb8Xk7Q= X-SA-Exim-Connect-IP: 68.227.174.4 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH 2/2] coredump: Allow coredumps to pipes to work with io_uring X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Now that io_uring like everything else stops for coredumps in get_signal the code can once again allow any interruptible condition after coredump_wait to interrupt the coredump. Clear TIF_NOTIFY_SIGNAL after coredump_wait, to guarantee that anything that sets TIF_NOTIFY_SIGNAL before coredump_wait completed won't cause the coredumps to interrupted. With all of the other threads in the process stopped io_uring doesn't call task_work_add on the thread running do_coredump. Combined with the clearing of TIF_NOTIFY_SIGNAL this allows processes that use io_uring to coredump through pipes. Restore dump_interrupted to be a simple call to signal_pending effectively reverting commit 06af8679449d ("coredump: Limit what can interrupt coredumps"). At this point only SIGKILL delivered to the coredumping thread should be able to cause signal_pending to return true. A nice followup would be to find a reliable race free way to modify task_work_add and probably set_notify_signal to skip setting TIF_NOTIFY_SIGNAL once it is clear a task will no longer process signals and other interruptible conditions. That would allow TIF_NOTIFY_SIGNAL to be cleared where TIF_SIGPENDING is cleared in coredump_zap_process. To be as certain as possible that this works, I tested this with commit 1d5f5ea7cb7d ("io-wq: remove worker to owner tw dependency") reverted. Which means that not only is TIF_NOTIFY_SIGNAL prevented from stopping coredumps to pipes, the sequence of stopping threads to participate in the coredump avoids deadlocks that were possible previously. Signed-off-by: "Eric W. Biederman" --- fs/coredump.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/coredump.c b/fs/coredump.c index 67dda77c500f..c06594f56cbb 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -476,7 +476,7 @@ static bool dump_interrupted(void) * but then we need to teach dump_write() to restart and clear * TIF_SIGPENDING. */ - return fatal_signal_pending(current) || freezing(current); + return signal_pending(current); } static void wait_for_dump_helpers(struct file *file) @@ -589,6 +589,9 @@ void do_coredump(const kernel_siginfo_t *siginfo) old_cred = override_creds(cred); + /* Don't break out of interruptible sleeps */ + clear_notify_signal(); + ispipe = format_corename(&cn, &cprm, &argv, &argc); if (ispipe) {