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,URIBL_BLOCKED,USER_AGENT_GIT 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 B1BEBC433E0 for ; Fri, 19 Jun 2020 16:45:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E1782158C for ; Fri, 19 Jun 2020 16:45:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592585110; bh=84hFvqnIv9RWd0djDh3w5bOVOFisJWS+WGdyjLQ/ADg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=XQqj+B0smciqxNZ3Q9L/2gUgWux0ycTlW1UiNtZHMRJ5SaO2fj5QNLW4g/NW+AXzJ 7fJ1nxOqqVnTzOroAPb1saKGuHHjmZ5QnEPUPQOa+BlS6TXaCu9hKUg3g5n3n/N5GM PMYd6Mt3TsjIDwedP+oMN0jKfWzOMJWUUyp/T3iA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388378AbgFSQpE (ORCPT ); Fri, 19 Jun 2020 12:45:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:33300 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387762AbgFSOme (ORCPT ); Fri, 19 Jun 2020 10:42:34 -0400 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 743E021582; Fri, 19 Jun 2020 14:42:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592577754; bh=84hFvqnIv9RWd0djDh3w5bOVOFisJWS+WGdyjLQ/ADg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=unGurp6r1kRIHKOViGARdvEiZu/5l5NNlp9D9gk6Yt6tIoekyQBYWsyBUccL/Elra xNO46SIeogixEbmVfLKSnCQ3GYguiN6w7HE7cYFWyO3QTBTMjPwTXGFkp22P2d2G1I ViNDSRFvBM5pnS2sUDvRBlIN0a3B5zZOmwMikZfA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 4.9 075/128] exit: Move preemption fixup up, move blocking operations down Date: Fri, 19 Jun 2020 16:32:49 +0200 Message-Id: <20200619141624.152006079@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200619141620.148019466@linuxfoundation.org> References: <20200619141620.148019466@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jann Horn [ Upstream commit 586b58cac8b4683eb58a1446fbc399de18974e40 ] With CONFIG_DEBUG_ATOMIC_SLEEP=y and CONFIG_CGROUPS=y, kernel oopses in non-preemptible context look untidy; after the main oops, the kernel prints a "sleeping function called from invalid context" report because exit_signals() -> cgroup_threadgroup_change_begin() -> percpu_down_read() can sleep, and that happens before the preempt_count_set(PREEMPT_ENABLED) fixup. It looks like the same thing applies to profile_task_exit() and kcov_task_exit(). Fix it by moving the preemption fixup up and the calls to profile_task_exit() and kcov_task_exit() down. Fixes: 1dc0fffc48af ("sched/core: Robustify preemption leak checks") Signed-off-by: Jann Horn Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200305220657.46800-1-jannh@google.com Signed-off-by: Sasha Levin --- kernel/exit.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index d9394fcd0e2c..27f4168eaeb1 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -739,8 +739,12 @@ void __noreturn do_exit(long code) int group_dead; TASKS_RCU(int tasks_rcu_i); - profile_task_exit(tsk); - kcov_task_exit(tsk); + /* + * We can get here from a kernel oops, sometimes with preemption off. + * Start by checking for critical errors. + * Then fix up important state like USER_DS and preemption. + * Then do everything else. + */ WARN_ON(blk_needs_flush_plug(tsk)); @@ -758,6 +762,16 @@ void __noreturn do_exit(long code) */ set_fs(USER_DS); + if (unlikely(in_atomic())) { + pr_info("note: %s[%d] exited with preempt_count %d\n", + current->comm, task_pid_nr(current), + preempt_count()); + preempt_count_set(PREEMPT_ENABLED); + } + + profile_task_exit(tsk); + kcov_task_exit(tsk); + ptrace_event(PTRACE_EVENT_EXIT, code); validate_creds_for_do_exit(tsk); @@ -794,13 +808,6 @@ void __noreturn do_exit(long code) */ raw_spin_unlock_wait(&tsk->pi_lock); - if (unlikely(in_atomic())) { - pr_info("note: %s[%d] exited with preempt_count %d\n", - current->comm, task_pid_nr(current), - preempt_count()); - preempt_count_set(PREEMPT_ENABLED); - } - /* sync mm's RSS info before statistics gathering */ if (tsk->mm) sync_mm_rss(tsk->mm); -- 2.25.1