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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 7B3A7FA3728 for ; Wed, 16 Oct 2019 22:14:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F2FE21925 for ; Wed, 16 Oct 2019 22:14:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571264084; bh=REzPX+ps4EsntGq1fEN2z9PLK2GMZpTroTB3Ljksu9A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=bR7X2J+sRRvD0qDxW7Gxt6xUl0qCxZsmBtpz4lSowT/1oZbh6by90x3Fhkp7jzEJP C1lH29JKw2vh7QjQZmsXFAEp28UWTKdB3mP/cfJH+EERbTcVH8/DcfTHXYLKhcdRzh b991H72iiHnBsLXMSl3ooKdFCFURAU20zf/Algmk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2439344AbfJPWOj (ORCPT ); Wed, 16 Oct 2019 18:14:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:46596 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2395244AbfJPVzk (ORCPT ); Wed, 16 Oct 2019 17:55:40 -0400 Received: from localhost (unknown [192.55.54.58]) (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 29D7B21A49; Wed, 16 Oct 2019 21:55:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571262939; bh=REzPX+ps4EsntGq1fEN2z9PLK2GMZpTroTB3Ljksu9A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SqSziGYBbE2YpvGxC9eb4EXoTBE4RijsMuOpNakre6C+K+iBfIT7OIVlZaCsUoyZf 3Fl6qRj3qyf3nv0G+mXMZbmbozTXumaFt3g6Z8cX6D99u483+4tZ6v8hzRCjHI9Mnd fbkU13TTeYVLc3N2L6yC7SO4mHFyIaLP8xvc2Ryw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Will Deacon , Xogium , Kees Cook , Russell King , Ingo Molnar , Petr Mladek , Feng Tang , Andrew Morton , Linus Torvalds Subject: [PATCH 4.14 01/65] panic: ensure preemption is disabled during panic() Date: Wed, 16 Oct 2019 14:50:15 -0700 Message-Id: <20191016214756.999293102@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191016214756.457746573@linuxfoundation.org> References: <20191016214756.457746573@linuxfoundation.org> User-Agent: quilt/0.66 X-stable: review X-Patchwork-Hint: ignore 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: Will Deacon commit 20bb759a66be52cf4a9ddd17fddaf509e11490cd upstream. Calling 'panic()' on a kernel with CONFIG_PREEMPT=y can leave the calling CPU in an infinite loop, but with interrupts and preemption enabled. From this state, userspace can continue to be scheduled, despite the system being "dead" as far as the kernel is concerned. This is easily reproducible on arm64 when booting with "nosmp" on the command line; a couple of shell scripts print out a periodic "Ping" message whilst another triggers a crash by writing to /proc/sysrq-trigger: | sysrq: Trigger a crash | Kernel panic - not syncing: sysrq triggered crash | CPU: 0 PID: 1 Comm: init Not tainted 5.2.15 #1 | Hardware name: linux,dummy-virt (DT) | Call trace: | dump_backtrace+0x0/0x148 | show_stack+0x14/0x20 | dump_stack+0xa0/0xc4 | panic+0x140/0x32c | sysrq_handle_reboot+0x0/0x20 | __handle_sysrq+0x124/0x190 | write_sysrq_trigger+0x64/0x88 | proc_reg_write+0x60/0xa8 | __vfs_write+0x18/0x40 | vfs_write+0xa4/0x1b8 | ksys_write+0x64/0xf0 | __arm64_sys_write+0x14/0x20 | el0_svc_common.constprop.0+0xb0/0x168 | el0_svc_handler+0x28/0x78 | el0_svc+0x8/0xc | Kernel Offset: disabled | CPU features: 0x0002,24002004 | Memory Limit: none | ---[ end Kernel panic - not syncing: sysrq triggered crash ]--- | Ping 2! | Ping 1! | Ping 1! | Ping 2! The issue can also be triggered on x86 kernels if CONFIG_SMP=n, otherwise local interrupts are disabled in 'smp_send_stop()'. Disable preemption in 'panic()' before re-enabling interrupts. Link: http://lkml.kernel.org/r/20191002123538.22609-1-will@kernel.org Link: https://lore.kernel.org/r/BX1W47JXPMR8.58IYW53H6M5N@dragonstone Signed-off-by: Will Deacon Reported-by: Xogium Reviewed-by: Kees Cook Cc: Russell King Cc: Greg Kroah-Hartman Cc: Ingo Molnar Cc: Petr Mladek Cc: Feng Tang Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- kernel/panic.c | 1 + 1 file changed, 1 insertion(+) --- a/kernel/panic.c +++ b/kernel/panic.c @@ -146,6 +146,7 @@ void panic(const char *fmt, ...) * after setting panic_cpu) from invoking panic() again. */ local_irq_disable(); + preempt_disable_notrace(); /* * It's possible to come here directly from a panic-assertion and