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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 EE86BC43381 for ; Fri, 22 Mar 2019 12:26:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BFD282054F for ; Fri, 22 Mar 2019 12:26:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553257610; bh=rLlyClE3k+8KDwmLyzc/9MOSbKiCr/NZy72U3v9eJNM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=PEyV57vtHfhm51f6OSrHcOVE+XeQjuGXJtyy+24EwjVYAqYuAYnyYmJEjK4nZ/yrR BvdNt6HHRQtBdZCwJIhoDqZmhq8Ie91Z6ts1m4dcQsdEpwr3IO6z8Zh9DdOth6wX1M Is09gKVlT7dUEEBR4UFKoXnrxqZEsFmBTb8IDzEE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390930AbfCVMWA (ORCPT ); Fri, 22 Mar 2019 08:22:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:32940 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390457AbfCVMWA (ORCPT ); Fri, 22 Mar 2019 08:22:00 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 9F7AA218A1; Fri, 22 Mar 2019 12:21:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553257319; bh=rLlyClE3k+8KDwmLyzc/9MOSbKiCr/NZy72U3v9eJNM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KDHMsMz8AIt9v2xYsZsz7wgWsqUxZxfHC8It3Fr3ezts4iknWqRf/LBOs8kj0tt1u lA153VDSEw39Oet3iifW/a/ifhKMg5fme73nkOuOJ77d93r/PQrZE7+Ns2m8JOelw3 xOdtbh4jbhEG4FaJrabDC84oepbelK/LAb57YKdE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Meelis Roos , Mathieu Malaterre , Michael Ellerman Subject: [PATCH 5.0 164/238] powerpc/ptrace: Simplify vr_get/set() to avoid GCC warning Date: Fri, 22 Mar 2019 12:16:23 +0100 Message-Id: <20190322111307.977949313@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190322111258.383569278@linuxfoundation.org> References: <20190322111258.383569278@linuxfoundation.org> User-Agent: quilt/0.65 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 5.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Michael Ellerman commit ca6d5149d2ad0a8d2f9c28cbe379802260a0a5e0 upstream. GCC 8 warns about the logic in vr_get/set(), which with -Werror breaks the build: In function ‘user_regset_copyin’, inlined from ‘vr_set’ at arch/powerpc/kernel/ptrace.c:628:9: include/linux/regset.h:295:4: error: ‘memcpy’ offset [-527, -529] is out of the bounds [0, 16] of object ‘vrsave’ with type ‘union ’ [-Werror=array-bounds] arch/powerpc/kernel/ptrace.c: In function ‘vr_set’: arch/powerpc/kernel/ptrace.c:623:5: note: ‘vrsave’ declared here } vrsave; This has been identified as a regression in GCC, see GCC bug 88273. However we can avoid the warning and also simplify the logic and make it more robust. Currently we pass -1 as end_pos to user_regset_copyout(). This says "copy up to the end of the regset". The definition of the regset is: [REGSET_VMX] = { .core_note_type = NT_PPC_VMX, .n = 34, .size = sizeof(vector128), .align = sizeof(vector128), .active = vr_active, .get = vr_get, .set = vr_set }, The end is calculated as (n * size), ie. 34 * sizeof(vector128). In vr_get/set() we pass start_pos as 33 * sizeof(vector128), meaning we can copy up to sizeof(vector128) into/out-of vrsave. The on-stack vrsave is defined as: union { elf_vrreg_t reg; u32 word; } vrsave; And elf_vrreg_t is: typedef __vector128 elf_vrreg_t; So there is no bug, but we rely on all those sizes lining up, otherwise we would have a kernel stack exposure/overwrite on our hands. Rather than relying on that we can pass an explict end_pos based on the sizeof(vrsave). The result should be exactly the same but it's more obviously not over-reading/writing the stack and it avoids the compiler warning. Reported-by: Meelis Roos Reported-by: Mathieu Malaterre Cc: stable@vger.kernel.org Tested-by: Mathieu Malaterre Tested-by: Meelis Roos Signed-off-by: Michael Ellerman Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/ptrace.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) --- a/arch/powerpc/kernel/ptrace.c +++ b/arch/powerpc/kernel/ptrace.c @@ -561,6 +561,7 @@ static int vr_get(struct task_struct *ta /* * Copy out only the low-order word of vrsave. */ + int start, end; union { elf_vrreg_t reg; u32 word; @@ -569,8 +570,10 @@ static int vr_get(struct task_struct *ta vrsave.word = target->thread.vrsave; + start = 33 * sizeof(vector128); + end = start + sizeof(vrsave); ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, &vrsave, - 33 * sizeof(vector128), -1); + start, end); } return ret; @@ -608,6 +611,7 @@ static int vr_set(struct task_struct *ta /* * We use only the first word of vrsave. */ + int start, end; union { elf_vrreg_t reg; u32 word; @@ -616,8 +620,10 @@ static int vr_set(struct task_struct *ta vrsave.word = target->thread.vrsave; + start = 33 * sizeof(vector128); + end = start + sizeof(vrsave); ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &vrsave, - 33 * sizeof(vector128), -1); + start, end); if (!ret) target->thread.vrsave = vrsave.word; }