From patchwork Fri Jan 12 00:47:29 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dan Williams X-Patchwork-Id: 10160261 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id F408460327 for ; Fri, 12 Jan 2018 11:30:12 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E0A8728986 for ; Fri, 12 Jan 2018 11:30:12 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D55D8289B0; Fri, 12 Jan 2018 11:30:12 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 3EA7028986 for ; Fri, 12 Jan 2018 11:30:11 +0000 (UTC) Received: (qmail 19945 invoked by uid 550); 12 Jan 2018 11:29:06 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Delivered-To: moderator for kernel-hardening@lists.openwall.com Received: (qmail 24079 invoked from network); 12 Jan 2018 00:55:46 -0000 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,346,1511856000"; d="scan'208";a="9761357" From: Dan Williams To: linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, kernel-hardening@lists.openwall.com, "Eric W. Biederman" , akpm@linux-foundation.org, torvalds@linux-foundation.org, tglx@linutronix.de, Elena Reshetova , alan@linux.intel.com Date: Thu, 11 Jan 2018 16:47:29 -0800 Message-ID: <151571804955.27429.6378685761369089453.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <151571798296.27429.7166552848688034184.stgit@dwillia2-desk3.amr.corp.intel.com> References: <151571798296.27429.7166552848688034184.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: StGit/0.17.1-9-g687f MIME-Version: 1.0 Subject: [kernel-hardening] [PATCH v2 12/19] userns: prevent bounds-check bypass via speculative execution X-Virus-Scanned: ClamAV using ClamSMTP Static analysis reports that 'pos' may be a user controlled value that is used as a data dependency determining which extent to return out of 'map'. In order to avoid potential leaks of kernel memory values, block speculative execution of the instruction stream that could issue further reads based on an invalid speculative result from 'm_start()'. Based on an original patch by Elena Reshetova. Cc: "Eric W. Biederman" Signed-off-by: Elena Reshetova Signed-off-by: Dan Williams --- kernel/user_namespace.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 246d4d4ce5c7..8c803eae186f 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include #include @@ -648,15 +649,13 @@ static void *m_start(struct seq_file *seq, loff_t *ppos, { loff_t pos = *ppos; unsigned extents = map->nr_extents; - smp_rmb(); - if (pos >= extents) - return NULL; + /* paired with smp_wmb in map_write */ + smp_rmb(); if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS) - return &map->extent[pos]; - - return &map->forward[pos]; + return array_ptr(map->extent, pos, extents); + return array_ptr(map->forward, pos, extents); } static void *uid_m_start(struct seq_file *seq, loff_t *ppos)