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=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 71587CA9EBD for ; Fri, 25 Oct 2019 18:11:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 45F8B21D7F for ; Fri, 25 Oct 2019 18:11:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731373AbfJYSGy (ORCPT ); Fri, 25 Oct 2019 14:06:54 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:46840 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731467AbfJYSFo (ORCPT ); Fri, 25 Oct 2019 14:05:44 -0400 Received: from [167.98.27.226] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1iO3xw-0008Ov-Rd; Fri, 25 Oct 2019 19:05:36 +0100 Received: from ben by deadeye with local (Exim 4.92.2) (envelope-from ) id 1iO3xv-0001jj-Va; Fri, 25 Oct 2019 19:05:35 +0100 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 , bp@alien8.de, "Dianzhang Chen" , "Thomas Gleixner" , hpa@zytor.com Date: Fri, 25 Oct 2019 19:03:29 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 28/47] x86/tls: Fix possible spectre-v1 in do_get_thread_area() In-Reply-To: X-SA-Exim-Connect-IP: 167.98.27.226 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 3.16.76-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Dianzhang Chen commit 993773d11d45c90cb1c6481c2638c3d9f092ea5b upstream. The index to access the threads tls array is controlled by userspace via syscall: sys_ptrace(), hence leading to a potential exploitation of the Spectre variant 1 vulnerability. The index can be controlled from: ptrace -> arch_ptrace -> do_get_thread_area. Fix this by sanitizing the user supplied index before using it to access the p->thread.tls_array. Signed-off-by: Dianzhang Chen Signed-off-by: Thomas Gleixner Cc: bp@alien8.de Cc: hpa@zytor.com Link: https://lkml.kernel.org/r/1561524630-3642-1-git-send-email-dianzhangchen0@gmail.com Signed-off-by: Ben Hutchings --- arch/x86/kernel/tls.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/arch/x86/kernel/tls.c +++ b/arch/x86/kernel/tls.c @@ -4,6 +4,7 @@ #include #include #include +#include #include #include @@ -177,6 +178,7 @@ int do_get_thread_area(struct task_struc struct user_desc __user *u_info) { struct user_desc info; + int index; if (idx == -1 && get_user(idx, &u_info->entry_number)) return -EFAULT; @@ -184,8 +186,11 @@ int do_get_thread_area(struct task_struc if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) return -EINVAL; - fill_user_desc(&info, idx, - &p->thread.tls_array[idx - GDT_ENTRY_TLS_MIN]); + index = idx - GDT_ENTRY_TLS_MIN; + index = array_index_nospec(index, + GDT_ENTRY_TLS_MAX - GDT_ENTRY_TLS_MIN + 1); + + fill_user_desc(&info, idx, &p->thread.tls_array[index]); if (copy_to_user(u_info, &info, sizeof(info))) return -EFAULT;