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 DEB69C11F67 for ; Mon, 28 Jun 2021 19:25:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C21BC61C92 for ; Mon, 28 Jun 2021 19:25:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236499AbhF1T2S (ORCPT ); Mon, 28 Jun 2021 15:28:18 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:32802 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233366AbhF1T2R (ORCPT ); Mon, 28 Jun 2021 15:28:17 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1lxwtB-0077lT-FQ; Mon, 28 Jun 2021 13:25:49 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95]:39208 helo=email.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 1lxwtA-00GC6G-Bf; Mon, 28 Jun 2021 13:25:49 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Kees Cook Cc: Linus Torvalds , Al Viro , Michael Schmitz , linux-arch , Jens Axboe , Oleg Nesterov , Linux Kernel Mailing List , Richard Henderson , Ivan Kokshaysky , Matt Turner , alpha , Geert Uytterhoeven , linux-m68k , Arnd Bergmann , Tejun Heo References: <87a6njf0ia.fsf@disp2133> <87tulpbp19.fsf@disp2133> <87zgvgabw1.fsf@disp2133> <875yy3850g.fsf_-_@disp2133> <874kdn6q87.fsf_-_@disp2133> <202106252038.389B963B6F@keescook> Date: Mon, 28 Jun 2021 14:25:41 -0500 In-Reply-To: <202106252038.389B963B6F@keescook> (Kees Cook's message of "Fri, 25 Jun 2021 20:42:06 -0700") Message-ID: <875yxxx03u.fsf@disp2133> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1lxwtA-00GC6G-Bf;;;mid=<875yxxx03u.fsf@disp2133>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/8u7v6yaAqNjosMDiG7hIGwsbaE7HP7qs= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 6/9] signal: Fold do_group_exit into get_signal fixing io_uring threads 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-kernel@vger.kernel.org Kees Cook writes: > On Thu, Jun 24, 2021 at 02:02:16PM -0500, Eric W. Biederman wrote: >> >> Forld do_group_exit into get_signal as it is the last caller. >> >> Move the group_exit logic above the PF_IO_WORKER exit, ensuring >> that if an PF_IO_WORKER catches SIGKILL every thread in >> the thread group will exit not just the the PF_IO_WORKER. >> >> Now that the information is easily available only set PF_SIGNALED >> when it was a signal that caused the exit. >> >> Signed-off-by: "Eric W. Biederman" >> --- >> include/linux/sched/task.h | 1 - >> kernel/exit.c | 31 ------------------------------- >> kernel/signal.c | 35 +++++++++++++++++++++++++---------- >> 3 files changed, 25 insertions(+), 42 deletions(-) >> >> diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h >> index ef02be869cf2..45525512e3d0 100644 >> --- a/include/linux/sched/task.h >> +++ b/include/linux/sched/task.h >> @@ -77,7 +77,6 @@ static inline void exit_thread(struct task_struct *tsk) >> { >> } >> #endif >> -extern void do_group_exit(int); >> >> extern void exit_files(struct task_struct *); >> extern void exit_itimers(struct signal_struct *); >> diff --git a/kernel/exit.c b/kernel/exit.c >> index 921519d80b56..635f434122b7 100644 >> --- a/kernel/exit.c >> +++ b/kernel/exit.c >> @@ -892,37 +892,6 @@ SYSCALL_DEFINE1(exit, int, error_code) >> do_exit((error_code&0xff)<<8); >> } >> >> -/* >> - * Take down every thread in the group. This is called by fatal signals >> - * as well as by sys_exit_group (below). >> - */ >> -void >> -do_group_exit(int exit_code) >> -{ >> - struct signal_struct *sig = current->signal; >> - >> - BUG_ON(exit_code & 0x80); /* core dumps don't get here */ >> - >> - if (signal_group_exit(sig)) >> - exit_code = sig->group_exit_code; >> - else if (!thread_group_empty(current)) { >> - struct sighand_struct *const sighand = current->sighand; >> - >> - spin_lock_irq(&sighand->siglock); >> - if (signal_group_exit(sig)) >> - /* Another thread got here before we took the lock. */ >> - exit_code = sig->group_exit_code; >> - else { >> - sig->group_exit_code = exit_code; >> - sig->flags = SIGNAL_GROUP_EXIT; >> - zap_other_threads(current); > > Oh, now I see it: the "new code" in start_group_exit() is an open-coded > zap_other_threads()? That wasn't clear to me, but makes sense now. Pretty much. I think zap_other_threads has actually muddied the waters quite a bit by putting reuse in the wrong place. >> - } >> - spin_unlock_irq(&sighand->siglock); >> - } >> - >> - do_exit(exit_code); >> - /* NOTREACHED */ >> -} >> >> /* >> * this kills every thread in the thread group. Note that any externally >> diff --git a/kernel/signal.c b/kernel/signal.c >> index c79c010ca5f3..95a076af600a 100644 >> --- a/kernel/signal.c >> +++ b/kernel/signal.c >> @@ -2646,6 +2646,7 @@ bool get_signal(struct ksignal *ksig) >> { >> struct sighand_struct *sighand = current->sighand; >> struct signal_struct *signal = current->signal; >> + int exit_code; >> int signr; >> >> if (unlikely(current->task_works)) >> @@ -2848,8 +2849,6 @@ bool get_signal(struct ksignal *ksig) >> /* >> * Anything else is fatal, maybe with a core dump. >> */ >> - current->flags |= PF_SIGNALED; >> - >> if (sig_kernel_coredump(signr)) { >> if (print_fatal_signals) >> print_fatal_signal(ksig->info.si_signo); >> @@ -2857,14 +2856,33 @@ bool get_signal(struct ksignal *ksig) >> /* >> * If it was able to dump core, this kills all >> * other threads in the group and synchronizes with >> - * their demise. If we lost the race with another >> - * thread getting here, it set group_exit_code >> - * first and our do_group_exit call below will use >> - * that value and ignore the one we pass it. >> + * their demise. If another thread makes it >> + * to do_coredump first, it will set group_exit_code >> + * which will be passed to do_exit. >> */ >> do_coredump(&ksig->info); >> } >> >> + /* >> + * Death signals, no core dump. >> + */ >> + exit_code = signr; >> + if (signal_group_exit(signal)) { >> + exit_code = signal->group_exit_code; >> + } else { >> + spin_lock_irq(&sighand->siglock); >> + if (signal_group_exit(signal)) { >> + /* Another thread got here before we took the lock. */ >> + exit_code = signal->group_exit_code; >> + } else { >> + start_group_exit_locked(signal, exit_code); > > And here's the "if we didn't already do start_group_exit(), do it here". > And that state is entirely captured via the SIGNAL_GROUP_EXIT flag. > Cool. Yes. At least when the dust clears. >> + } >> + spin_unlock_irq(&sighand->siglock); >> + } >> + >> + if (exit_code & 0x7f) >> + current->flags |= PF_SIGNALED; >> + >> /* >> * PF_IO_WORKER threads will catch and exit on fatal signals >> * themselves. They have cleanup that must be performed, so >> @@ -2873,10 +2891,7 @@ bool get_signal(struct ksignal *ksig) >> if (current->flags & PF_IO_WORKER) >> goto out; >> >> - /* >> - * Death signals, no core dump. >> - */ >> - do_group_exit(ksig->info.si_signo); >> + do_exit(exit_code); >> /* NOTREACHED */ >> } >> spin_unlock_irq(&sighand->siglock); >> -- >> 2.20.1 >>