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=-2.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 02AB3C43144 for ; Thu, 28 Jun 2018 16:24:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AFBD727670 for ; Thu, 28 Jun 2018 16:24:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="pJwO8rQW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AFBD727670 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=efficios.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753351AbeF1QYU (ORCPT ); Thu, 28 Jun 2018 12:24:20 -0400 Received: from mail.efficios.com ([167.114.142.138]:34558 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752981AbeF1QYP (ORCPT ); Thu, 28 Jun 2018 12:24:15 -0400 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 3745422E770; Thu, 28 Jun 2018 12:24:14 -0400 (EDT) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id LvB0bLZQdvx2; Thu, 28 Jun 2018 12:24:13 -0400 (EDT) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 9DD3322E76D; Thu, 28 Jun 2018 12:24:13 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 9DD3322E76D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1530203053; bh=kJ3g3D83FnWKmKKsBpugLKb7HsAwEC6B5XuK99Rl3j0=; h=From:To:Date:Message-Id; b=pJwO8rQW1Wmp6nw5GBXVte24Tq87EQ4wWlmf135gkrrvbyIQJ/WRzF7xMPPf3mfoU 2XR+BAgl0wkLtSE+PO2/q+cnKRTljUqIQXEj8mG4zZrfrCZlsbeLsEvUry9WGzU73S sjsh5U7INtINUq1xIsxlYYmkOOxBTv2245wT/D+yFiVX8kuLGdWvVkp0sA7ZjMendU 6fi057WB4mdvIG3G2zdaI6sH0+fEYAoQOX9yA2kcvMbQpuKOFvGtPILys1gOj8M4o+ VKvoWUN14c3khbx+ssJ57K8PWag2PlJR0+50xXLBpX+usCs2aJPHWiliLyjUdf6aHR l+65LtRKDSCjg== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10026) with ESMTP id R6D_-40g4R5N; Thu, 28 Jun 2018 12:24:13 -0400 (EDT) Received: from thinkos.internal.efficios.com (192-222-157-41.qc.cable.ebox.net [192.222.157.41]) by mail.efficios.com (Postfix) with ESMTPSA id 4643622E75B; Thu, 28 Jun 2018 12:24:13 -0400 (EDT) From: Mathieu Desnoyers To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Peter Zijlstra , "Paul E . McKenney" , Boqun Feng , Andy Lutomirski , Dave Watson , Paul Turner , Andrew Morton , Russell King , Ingo Molnar , "H . Peter Anvin" , Andi Kleen , Chris Lameter , Ben Maurer , Steven Rostedt , Josh Triplett , Linus Torvalds , Catalin Marinas , Will Deacon , Michael Kerrisk , Joel Fernandes , Mathieu Desnoyers Subject: [RFC PATCH for 4.18 2/2] rseq: check that rseq->rseq_cs padding is zero Date: Thu, 28 Jun 2018 12:23:59 -0400 Message-Id: <20180628162359.9054-2-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20180628162359.9054-1-mathieu.desnoyers@efficios.com> References: <20180628162359.9054-1-mathieu.desnoyers@efficios.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 32-bit kernels, the rseq->rseq_cs_padding field is never read by the kernel. However, 64-bit kernels dealing with 32-bit compat tasks read the full 64-bit in its entirety, and terminates the offending process with a segmentation fault if the upper 32 bits are set due to failure of copy_from_user(). Ensure that both 32-bit and 64-bit kernels dealing with 32-bit tasks end up terminating offending tasks with a segmentation fault if the upper 32-bit padding bits (rseq->rseq_cs_padding) are set by adding an explicit check that padding is zero on 32-bit kernels. Signed-off-by: Mathieu Desnoyers CC: "Paul E. McKenney" CC: Peter Zijlstra CC: Paul Turner CC: Thomas Gleixner CC: Andy Lutomirski CC: Andi Kleen CC: Dave Watson CC: Chris Lameter CC: Ingo Molnar CC: "H. Peter Anvin" CC: Ben Maurer CC: Steven Rostedt CC: Josh Triplett CC: Linus Torvalds CC: Andrew Morton CC: Russell King CC: Catalin Marinas CC: Will Deacon CC: Michael Kerrisk CC: Boqun Feng CC: linux-api@vger.kernel.org --- kernel/rseq.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/kernel/rseq.c b/kernel/rseq.c index 4ba582046fcd..b038f35a60d6 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -112,6 +112,29 @@ static int rseq_reset_rseq_cpu_id(struct task_struct *t) return 0; } +#ifndef __LP64__ +/* + * Ensure that padding is zero. + */ +static int check_rseq_cs_padding(struct task_struct *t) +{ + unsigned long pad; + int ret; + + ret = __get_user(pad, &t->rseq->rseq_cs_padding); + if (ret) + return ret; + if (pad) + return -EFAULT; + return 0; +} +#else +static int check_rseq_cs_padding(struct task_struct *t) +{ + return 0; +} +#endif + static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) { struct rseq_cs __user *urseq_cs; @@ -123,6 +146,8 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) ret = __get_user(ptr, &t->rseq->rseq_cs); if (ret) return ret; + if (check_rseq_cs_padding(t)) + return -EFAULT; if (!ptr) { memset(rseq_cs, 0, sizeof(*rseq_cs)); return 0; -- 2.11.0