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 1DEFAC43381 for ; Fri, 22 Mar 2019 12:52:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E15A821873 for ; Fri, 22 Mar 2019 12:52:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553259140; bh=pN/A+MOnhI3ujxG9a6UmmFozemMJhARZgwYxSjjQcTQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=vVZAygDv4KZMlkvXFFYAdUK3JFY3xBWqh3a1n9uoJJb64WpJuiXKHKghnr/MzXqzy QhEc0Q5p3nLm4qNoUAhrArZe8A5zXcj5fzFQrnWWoYtkGcyCscO7CsudnqeNAwTc9N k0oU9qELnqZFuwFNpzCIKdQdUPJHjyGs1yu8peEs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732402AbfCVLxa (ORCPT ); Fri, 22 Mar 2019 07:53:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:57692 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732221AbfCVLxa (ORCPT ); Fri, 22 Mar 2019 07:53:30 -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 7A1B020850; Fri, 22 Mar 2019 11:53:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553255609; bh=pN/A+MOnhI3ujxG9a6UmmFozemMJhARZgwYxSjjQcTQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ntKJ01qWzgg4Po10fHHLNP9REW7VqNdmfC52fJ/aArBAvVgaekAz0hhI37jvDDWk4 kCr3oP/zZJFy27wpNQzetc3Z2JgVmLGZuIAzCCgJews34AFCGyaboY/rgVHMgKy/c0 AawHpabV5I+LuO8iMpzX9hCMO4HG3Qjwdj6LwtGM= 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 4.14 143/183] powerpc/ptrace: Simplify vr_get/set() to avoid GCC warning Date: Fri, 22 Mar 2019 12:16:11 +0100 Message-Id: <20190322111252.136172126@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190322111241.819468003@linuxfoundation.org> References: <20190322111241.819468003@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 4.14-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 @@ -547,6 +547,7 @@ 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; @@ -555,8 +556,10 @@ 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; @@ -594,6 +597,7 @@ 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; @@ -602,8 +606,10 @@ 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; }