From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 03 Jul 2017 15:42:23 +0200 (CEST) Received: from mail.linuxfoundation.org ([140.211.169.12]:38564 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S23994767AbdGCNltlyVqi (ORCPT ); Mon, 3 Jul 2017 15:41:49 +0200 Received: from localhost (LFbn-1-12253-150.w90-92.abo.wanadoo.fr [90.92.67.150]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 87E2692B; Mon, 3 Jul 2017 13:41:43 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, James Hogan , linux-mips@linux-mips.org, Ralf Baechle Subject: [PATCH 4.9 034/172] MIPS: Avoid accidental raw backtrace Date: Mon, 3 Jul 2017 15:33:34 +0200 Message-Id: <20170703133415.850691358@linuxfoundation.org> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170703133414.260777365@linuxfoundation.org> References: <20170703133414.260777365@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 58998 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: gregkh@linuxfoundation.org Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: James Hogan commit 854236363370995a609a10b03e35fd3dc5e9e4a1 upstream. Since commit 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with usermode") show_backtrace() invokes the raw backtracer when cp0_status & ST0_KSU indicates user mode to fix issues on EVA kernels where user and kernel address spaces overlap. However this is used by show_stack() which creates its own pt_regs on the stack and leaves cp0_status uninitialised in most of the code paths. This results in the non deterministic use of the raw back tracer depending on the previous stack content. show_stack() deals exclusively with kernel mode stacks anyway, so explicitly initialise regs.cp0_status to KSU_KERNEL (i.e. 0) to ensure we get a useful backtrace. Fixes: 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with usermode") Signed-off-by: James Hogan Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/16656/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman --- arch/mips/kernel/traps.c | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -199,6 +199,8 @@ void show_stack(struct task_struct *task { struct pt_regs regs; mm_segment_t old_fs = get_fs(); + + regs.cp0_status = KSU_KERNEL; if (sp) { regs.regs[29] = (unsigned long)sp; regs.regs[31] = 0;