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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 54E37C35240 for ; Wed, 29 Jan 2020 19:12:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3265820716 for ; Wed, 29 Jan 2020 19:12:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580325126; bh=ZznyVoYeo/nOfJUiB0+J9gkC+ikPfyQGiotvsICxSPs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=slBMmJYGdqFhcCnmIc7zRofKsB8pp/G4CZhi3rcVcdNMS3JIjeM9kWBHngLPeI3dT PNSwjdC9YrDPkAxJNwCKxz2GiFje+sX58JGHZUVpJYM3BBhpTVwLmUwp7H8rbDGnax W5okhXrUnde/qULe3V23GshCRMpOcFwvmxAmGiXE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727654AbgA2TMF (ORCPT ); Wed, 29 Jan 2020 14:12:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:33264 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726183AbgA2TMF (ORCPT ); Wed, 29 Jan 2020 14:12:05 -0500 Received: from localhost (unknown [155.52.187.28]) (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 53DF6205F4; Wed, 29 Jan 2020 19:12:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580325124; bh=ZznyVoYeo/nOfJUiB0+J9gkC+ikPfyQGiotvsICxSPs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oV+Jug30rmSiFU85nWkPUIYxzQ+8qnaR0/FLP1fB1ooLq87uZR1vfXKUnbR0ZG9P+ UzNIN/LnvIHoROapa8zHt6wM88fcpUPc/02uilPpxeOm+zF7w9w41Q12rpszvLW6us OZ3BldRQhO+7ZQC+0cnVjYwmuk6fXlWHnBCpltTE= Date: Wed, 29 Jan 2020 14:12:03 -0500 From: Sasha Levin To: Greg Kroah-Hartman Cc: Thomas Voegtle , linux-kernel@vger.kernel.org, stable@vger.kernel.org, ronnie sahlberg , Christoph =?iso-8859-1?Q?B=F6hmwalder?= , Steve French , Philipp Reisner , David Laight , "Eric W. Biederman" Subject: Re: [PATCH 4.9 183/271] signal: Allow cifs and drbd to receive their terminating signals Message-ID: <20200129191203.GA2896@sasha-vm> References: <20200128135852.449088278@linuxfoundation.org> <20200128135906.176803329@linuxfoundation.org> <20200129113643.GB5277@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200129113643.GB5277@kroah.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 29, 2020 at 12:36:43PM +0100, Greg Kroah-Hartman wrote: >On Wed, Jan 29, 2020 at 12:10:47PM +0100, Thomas Voegtle wrote: >> On Tue, 28 Jan 2020, Greg Kroah-Hartman wrote: >> >> > 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") >> >> These two commits come with that release, but... >> >> > Fixes: fee109901f39 ("signal/drbd: Use send_sig not force_sig") >> > Fixes: 3cf5d076fb4d ("signal: Remove task parameter from force_sig") >> >> ...these two commits not and were never added to 4.9.y. >> >> Are these both really not needed? > >I don't think so, do you feel otherwise? Both of those commits read as a cleanup to me. I've actually slightly modified to patch to not need those commits (they were less than trivial to backport as is). -- Thanks, Sasha