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 213ABFA3728 for ; Wed, 16 Oct 2019 22:04:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E697A20872 for ; Wed, 16 Oct 2019 22:04:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571263496; bh=oTJy7g+65jfw8O95lyTxiNicEh8O3hRg7zwVhatUbeM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=1aEJ61FJ1A7aa3WJp9tJH7wSLg6VyEnjGO3rB1GzZcub8T98C2n+EkDqvEGKRhlL7 bNQzwnM4240JcDxgChBoanPAmrqZCE/TTvfGOGvsQ5p36PMfYM0IiDyT59qqWxBC6C lccTtkhyWkbNuUUiWUuy2Nk2BQGPJQvjdA7dAqkE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2438337AbfJPV65 (ORCPT ); Wed, 16 Oct 2019 17:58:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:51430 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2438115AbfJPV6J (ORCPT ); Wed, 16 Oct 2019 17:58:09 -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 74CE521D7A; Wed, 16 Oct 2019 21:58:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571263088; bh=oTJy7g+65jfw8O95lyTxiNicEh8O3hRg7zwVhatUbeM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=k4LheC/xHTIhvSq55BGt9/i8ZkCIePXL8K8I3WBM4LXzRXm/bHGr+7YJZdWZZHmmH UqMIJid2BUTl0RETy2v7ZCSYzBE8fZyby8X1zQ4MIq2pKD0nZnwzeuZ3M+3d8Ccu+f 9QI94rtbvUy0Fn6nbAqZlQr7Km258qf2KkUcf2GI= 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 5.3 001/112] panic: ensure preemption is disabled during panic() Date: Wed, 16 Oct 2019 14:49:53 -0700 Message-Id: <20191016214844.262811710@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191016214844.038848564@linuxfoundation.org> References: <20191016214844.038848564@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: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 @@ -179,6 +179,7 @@ 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