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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 AA7E6C28CC6 for ; Wed, 5 Jun 2019 09:25:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B2DC20717 for ; Wed, 5 Jun 2019 09:25:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726960AbfFEJZc (ORCPT ); Wed, 5 Jun 2019 05:25:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54579 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726502AbfFEJZc (ORCPT ); Wed, 5 Jun 2019 05:25:32 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AAA2283F51; Wed, 5 Jun 2019 09:25:27 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.159]) by smtp.corp.redhat.com (Postfix) with SMTP id F0156600CC; Wed, 5 Jun 2019 09:25:18 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 5 Jun 2019 11:25:26 +0200 (CEST) Date: Wed, 5 Jun 2019 11:25:17 +0200 From: Oleg Nesterov To: David Laight Cc: 'Linus Torvalds' , Andrew Morton , Deepa Dinamani , Linux List Kernel Mailing , Arnd Bergmann , Davidlohr Bueso , Jens Axboe , Davidlohr Bueso , "e@80x24.org" , Jason Baron , linux-fsdevel , "linux-aio@kvack.org" , "omar.kilani@gmail.com" , Thomas Gleixner , stable , Al Viro , "Eric W. Biederman" Subject: Re: [PATCH] signal: remove the wrong signal_pending() check in restore_user_sigmask() Message-ID: <20190605092516.GC32406@redhat.com> References: <20190522032144.10995-1-deepa.kernel@gmail.com> <20190529161157.GA27659@redhat.com> <20190604134117.GA29963@redhat.com> <263d0e478ee447d9aa10baab0d8673a5@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <263d0e478ee447d9aa10baab0d8673a5@AcuMS.aculab.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Wed, 05 Jun 2019 09:25:32 +0000 (UTC) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 06/05, David Laight wrote: > > epoll() would have: > if (restore_user_sigmask(xxx.sigmask, &sigsaved, !ret || ret == -EINTR)) > ret = -EINTR; I don't think so but lets discuss this later. > I also think it could be simplified if code that loaded the 'user sigmask' > saved the old one in 'current->saved_sigmask' (and saved that it had done it). > You'd not need 'sigsaved' nor pass the user sigmask address into > the restore function. Heh. apparently you do not read my emails ;) This is what I proposed in my very 1st email, and I even showed the patch and the code with the patch applied twice. Let me do this again. Let me show the code with the patch applied. I am using epoll_pwait() as an example because it looks very simple. static inline void set_restore_sigmask(void) { // WARN_ON(!TIF_SIGPENDING) was removed by this patch current->restore_sigmask = true; } int set_xxx(const sigset_t __user *umask, size_t sigsetsize) { sigset_t *kmask; if (!umask) return 0; if (sigsetsize != sizeof(sigset_t)) return -EINVAL; if (copy_from_user(kmask, umask, sizeof(sigset_t))) return -EFAULT; // we can safely modify ->saved_sigmask/restore_sigmask, they has no meaning // until the syscall returns. set_restore_sigmask(); current->saved_sigmask = current->blocked; set_current_blocked(kmask); return 0; } void update_xxx(bool interrupted) { // the main reason for this helper is WARN_ON(!TIF_SIGPENDING) which was "moved" // from set_restore_sigmask() above. if (interrupted) WARN_ON(!test_thread_flag(TIF_SIGPENDING)); else restore_saved_sigmask(); } SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, int, maxevents, int, timeout, const sigset_t __user *, sigmask, size_t, sigsetsize) { int error; error = set_xxx(sigmask, sigsetsize); if (error) return error; error = do_epoll_wait(epfd, events, maxevents, timeout); update_xxx(error == -EINTR); return error; } Oleg.