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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 14075C282DD for ; Wed, 8 Jan 2020 19:46:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E471E2082E for ; Wed, 8 Jan 2020 19:46:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730635AbgAHTqW (ORCPT ); Wed, 8 Jan 2020 14:46:22 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43704 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730461AbgAHTqE (ORCPT ); Wed, 8 Jan 2020 14:46:04 -0500 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1ipHHE-0006p9-49; Wed, 08 Jan 2020 19:46:00 +0000 Received: from ben by deadeye with local (Exim 4.93) (envelope-from ) id 1ipHHC-007doE-UT; Wed, 08 Jan 2020 19:45:58 +0000 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Will Deacon" , "Mark Rutland" , "Catalin Marinas" Date: Wed, 08 Jan 2020 19:43:45 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 47/63] arm64: debug: Ensure debug handlers check triggering exception level In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.81-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Will Deacon commit 6bd288569b50bc89fa5513031086746968f585cb upstream. Debug exception handlers may be called for exceptions generated both by user and kernel code. In many cases, this is checked explicitly, but in other cases things either happen to work by happy accident or they go slightly wrong. For example, executing 'brk #4' from userspace will enter the kprobes code and be ignored, but the instruction will be retried forever in userspace instead of delivering a SIGTRAP. Fix this issue in the most stable-friendly fashion by simply adding explicit checks of the triggering exception level to all of our debug exception handlers. Reviewed-by: Mark Rutland Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas Signed-off-by: Ben Hutchings --- arch/arm64/kernel/kgdb.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c index bcac81e600b9..f72743dc070d 100644 --- a/arch/arm64/kernel/kgdb.c +++ b/arch/arm64/kernel/kgdb.c @@ -215,22 +215,31 @@ int kgdb_arch_handle_exception(int exception_vector, int signo, static int kgdb_brk_fn(struct pt_regs *regs, unsigned int esr) { + if (user_mode(regs)) + return DBG_HOOK_ERROR; + kgdb_handle_exception(1, SIGTRAP, 0, regs); - return 0; + return DBG_HOOK_HANDLED; } static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int esr) { + if (user_mode(regs)) + return DBG_HOOK_ERROR; + compiled_break = 1; kgdb_handle_exception(1, SIGTRAP, 0, regs); - return 0; + return DBG_HOOK_HANDLED; } static int kgdb_step_brk_fn(struct pt_regs *regs, unsigned int esr) { + if (user_mode(regs)) + return DBG_HOOK_ERROR; + kgdb_handle_exception(1, SIGTRAP, 0, regs); - return 0; + return DBG_HOOK_HANDLED; } static struct break_hook kgdb_brkpt_hook = {