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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 A9DB1C2D0DB for ; Tue, 28 Jan 2020 14:36:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 779EE2467E for ; Tue, 28 Jan 2020 14:36:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580222168; bh=2yTldlziUHYWNFg6KPuTlYPHjN0Cr21TjKkc0RitqoM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=R3lDe9nza5jApIdVWH/f/GSs3qigrYfr4snp5ZmfKfDnNkK97M2y8BhW/Qz2f+/Kg 0VOxKB82gp9W6KaFaxuDeBw3Nfvxx1ZVUU9ghTzcKoLWVfhojEhUcegTy0Onnq5DDv MPXc1JdS3bOPzEp0p5Zf7MfcqRlrHaNuR2SPB6LI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731543AbgA1OWX (ORCPT ); Tue, 28 Jan 2020 09:22:23 -0500 Received: from mail.kernel.org ([198.145.29.99]:48076 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725997AbgA1OWT (ORCPT ); Tue, 28 Jan 2020 09:22:19 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A37002469A; Tue, 28 Jan 2020 14:22:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580221338; bh=2yTldlziUHYWNFg6KPuTlYPHjN0Cr21TjKkc0RitqoM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OEZr0pXycSPMJhSLUoIpMYyy/ZBnDz0OIy9VjwiwF7qCdGbdV5Tz82dHoAPxbQCAN N6ON8Vev7QGiaR10yOHD7OLqcvpwnY2TA3tToZs4dkQcLiFNdnw6chNchhUee2e0Ub NpxA5Dgsz3knhahkk/BomK4BEKE6JXBWmpj0P4aU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, ronnie sahlberg , =?UTF-8?q?Christoph=20B=C3=B6hmwalder?= , Steve French , Philipp Reisner , David Laight , "Eric W. Biederman" , Sasha Levin Subject: [PATCH 4.9 183/271] signal: Allow cifs and drbd to receive their terminating signals Date: Tue, 28 Jan 2020 15:05:32 +0100 Message-Id: <20200128135906.176803329@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200128135852.449088278@linuxfoundation.org> References: <20200128135852.449088278@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric W. Biederman [ Upstream commit 33da8e7c814f77310250bb54a9db36a44c5de784 ] My recent to change to only use force_sig for a synchronous events wound up breaking signal reception cifs and drbd. I had overlooked the fact that by default kthreads start out with all signals set to SIG_IGN. So a change I thought was safe turned out to have made it impossible for those kernel thread to catch their signals. Reverting the work on force_sig is a bad idea because what the code was doing was very much a misuse of force_sig. As the way force_sig ultimately allowed the signal to happen was to change the signal handler to SIG_DFL. Which after the first signal will allow userspace to send signals to these kernel threads. At least for wake_ack_receiver in drbd that does not appear actively wrong. So correct this problem by adding allow_kernel_signal that will allow signals whose siginfo reports they were sent by the kernel through, but will not allow userspace generated signals, and update cifs and drbd to call allow_kernel_signal in an appropriate place so that their thread can receive this signal. Fixing things this way ensures that userspace won't be able to send signals and cause problems, that it is clear which signals the threads are expecting to receive, and it guarantees that nothing else in the system will be affected. This change was partly inspired by similar cifs and drbd patches that added allow_signal. Reported-by: ronnie sahlberg Reported-by: Christoph Böhmwalder Tested-by: Christoph Böhmwalder Cc: Steve French Cc: Philipp Reisner Cc: David Laight Fixes: 247bc9470b1e ("cifs: fix rmmod regression in cifs.ko caused by force_sig changes") Fixes: 72abe3bcf091 ("signal/cifs: Fix cifs_put_tcp_session to call send_sig instead of force_sig") Fixes: fee109901f39 ("signal/drbd: Use send_sig not force_sig") Fixes: 3cf5d076fb4d ("signal: Remove task parameter from force_sig") Signed-off-by: "Eric W. Biederman" Signed-off-by: Sasha Levin --- drivers/block/drbd/drbd_main.c | 2 ++ fs/cifs/connect.c | 2 +- include/linux/signal.h | 15 ++++++++++++++- kernel/signal.c | 5 +++++ 4 files changed, 22 insertions(+), 2 deletions(-) diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c index f5c24459fc5c1..daa9cef96ec66 100644 --- a/drivers/block/drbd/drbd_main.c +++ b/drivers/block/drbd/drbd_main.c @@ -332,6 +332,8 @@ static int drbd_thread_setup(void *arg) thi->name[0], resource->name); + allow_kernel_signal(DRBD_SIGKILL); + allow_kernel_signal(SIGXCPU); restart: retval = thi->function(thi); diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 7d46025d5e899..751bdde6515d5 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -885,7 +885,7 @@ cifs_demultiplex_thread(void *p) mempool_resize(cifs_req_poolp, length + cifs_min_rcv); set_freezable(); - allow_signal(SIGKILL); + allow_kernel_signal(SIGKILL); while (server->tcpStatus != CifsExiting) { if (try_to_freeze()) continue; diff --git a/include/linux/signal.h b/include/linux/signal.h index 5308304993bea..ffa58ff53e225 100644 --- a/include/linux/signal.h +++ b/include/linux/signal.h @@ -313,6 +313,9 @@ extern void signal_setup_done(int failed, struct ksignal *ksig, int stepping); extern void exit_signals(struct task_struct *tsk); extern void kernel_sigaction(int, __sighandler_t); +#define SIG_KTHREAD ((__force __sighandler_t)2) +#define SIG_KTHREAD_KERNEL ((__force __sighandler_t)3) + static inline void allow_signal(int sig) { /* @@ -320,7 +323,17 @@ static inline void allow_signal(int sig) * know it'll be handled, so that they don't get converted to * SIGKILL or just silently dropped. */ - kernel_sigaction(sig, (__force __sighandler_t)2); + kernel_sigaction(sig, SIG_KTHREAD); +} + +static inline void allow_kernel_signal(int sig) +{ + /* + * Kernel threads handle their own signals. Let the signal code + * know signals sent by the kernel will be handled, so that they + * don't get silently dropped. + */ + kernel_sigaction(sig, SIG_KTHREAD_KERNEL); } static inline void disallow_signal(int sig) diff --git a/kernel/signal.c b/kernel/signal.c index 30914b3c76b21..57fadbe69c2e6 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -79,6 +79,11 @@ static int sig_task_ignored(struct task_struct *t, int sig, bool force) handler == SIG_DFL && !(force && sig_kernel_only(sig))) return 1; + /* Only allow kernel generated signals to this kthread */ + if (unlikely((t->flags & PF_KTHREAD) && + (handler == SIG_KTHREAD_KERNEL) && !force)) + return true; + return sig_handler_ignored(handler, sig); } -- 2.20.1