From patchwork Fri May 5 18:32:10 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 9714225 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 081486034B for ; Fri, 5 May 2017 18:52:25 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F0A192861C for ; Fri, 5 May 2017 18:52:24 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E54892863A; Fri, 5 May 2017 18:52:24 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9A0532861C for ; Fri, 5 May 2017 18:52:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753205AbdEESvj (ORCPT ); Fri, 5 May 2017 14:51:39 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:58310 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751997AbdEESdO (ORCPT ); Fri, 5 May 2017 14:33:14 -0400 Received: from localhost (unknown [104.132.0.100]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id B620BBFA; Fri, 5 May 2017 18:33:13 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Paul Menzel , Josh Poimboeuf , "Steven Rostedt (VMware)" , "Rafael J . Wysocki" , linux-acpi@vger.kernel.org, Borislav Petkov , Len Brown , Thomas Gleixner Subject: [PATCH 3.18 25/68] ftrace/x86: Fix triple fault with graph tracing and suspend-to-ram Date: Fri, 5 May 2017 11:32:10 -0700 Message-Id: <20170505183213.604181274@linuxfoundation.org> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170505183212.587141964@linuxfoundation.org> References: <20170505183212.587141964@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Josh Poimboeuf commit 34a477e5297cbaa6ecc6e17c042a866e1cbe80d6 upstream. On x86-32, with CONFIG_FIRMWARE and multiple CPUs, if you enable function graph tracing and then suspend to RAM, it will triple fault and reboot when it resumes. The first fault happens when booting a secondary CPU: startup_32_smp() load_ucode_ap() prepare_ftrace_return() ftrace_graph_is_dead() (accesses 'kill_ftrace_graph') The early head_32.S code calls into load_ucode_ap(), which has an an ftrace hook, so it calls prepare_ftrace_return(), which calls ftrace_graph_is_dead(), which tries to access the global 'kill_ftrace_graph' variable with a virtual address, causing a fault because the CPU is still in real mode. The fix is to add a check in prepare_ftrace_return() to make sure it's running in protected mode before continuing. The check makes sure the stack pointer is a virtual kernel address. It's a bit of a hack, but it's not very intrusive and it works well enough. For reference, here are a few other (more difficult) ways this could have potentially been fixed: - Move startup_32_smp()'s call to load_ucode_ap() down to *after* paging is enabled. (No idea what that would break.) - Track down load_ucode_ap()'s entire callee tree and mark all the functions 'notrace'. (Probably not realistic.) - Pause graph tracing in ftrace_suspend_notifier_call() or bringup_cpu() or __cpu_up(), and ensure that the pause facility can be queried from real mode. Reported-by: Paul Menzel Signed-off-by: Josh Poimboeuf Tested-by: Paul Menzel Reviewed-by: Steven Rostedt (VMware) Cc: "Rafael J . Wysocki" Cc: linux-acpi@vger.kernel.org Cc: Borislav Petkov Cc: Len Brown Link: http://lkml.kernel.org/r/5c1272269a580660703ed2eccf44308e790c7a98.1492123841.git.jpoimboe@redhat.com Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/ftrace.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -703,6 +703,18 @@ void prepare_ftrace_return(unsigned long unsigned long return_hooker = (unsigned long) &return_to_handler; + /* + * When resuming from suspend-to-ram, this function can be indirectly + * called from early CPU startup code while the CPU is in real mode, + * which would fail miserably. Make sure the stack pointer is a + * virtual address. + * + * This check isn't as accurate as virt_addr_valid(), but it should be + * good enough for this purpose, and it's fast. + */ + if (unlikely((long)__builtin_frame_address(0) >= 0)) + return; + if (unlikely(ftrace_graph_is_dead())) return;