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=-2.8 required=3.0 tests=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 E93D6C4321E for ; Fri, 7 Sep 2018 21:41:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AA09320844 for ; Fri, 7 Sep 2018 21:41:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AA09320844 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org 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 S1730239AbeIHCYF (ORCPT ); Fri, 7 Sep 2018 22:24:05 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:54852 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728220AbeIHCYE (ORCPT ); Fri, 7 Sep 2018 22:24:04 -0400 Received: from localhost (ip-213-127-74-90.ip.prioritytelecom.net [213.127.74.90]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id DCFA61010; Fri, 7 Sep 2018 21:41:08 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , Christian Brauner , Serge Hallyn , "Eric W. Biederman" Subject: [PATCH 4.4 34/47] userns: move user access out of the mutex Date: Fri, 7 Sep 2018 23:10:30 +0200 Message-Id: <20180907210908.241189276@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180907210904.607934824@linuxfoundation.org> References: <20180907210904.607934824@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn commit 5820f140edef111a9ea2ef414ab2428b8cb805b1 upstream. The old code would hold the userns_state_mutex indefinitely if memdup_user_nul stalled due to e.g. a userfault region. Prevent that by moving the memdup_user_nul in front of the mutex_lock(). Note: This changes the error precedence of invalid buf/count/*ppos vs map already written / capabilities missing. Fixes: 22d917d80e84 ("userns: Rework the user_namespace adding uid/gid...") Cc: stable@vger.kernel.org Signed-off-by: Jann Horn Acked-by: Christian Brauner Acked-by: Serge Hallyn Signed-off-by: Eric W. Biederman Signed-off-by: Greg Kroah-Hartman --- kernel/user_namespace.c | 22 ++++++++++------------ 1 file changed, 10 insertions(+), 12 deletions(-) --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -604,7 +604,16 @@ static ssize_t map_write(struct file *fi struct uid_gid_extent *extent = NULL; unsigned long page = 0; char *kbuf, *pos, *next_line; - ssize_t ret = -EINVAL; + ssize_t ret; + + /* Only allow < page size writes at the beginning of the file */ + if ((*ppos != 0) || (count >= PAGE_SIZE)) + return -EINVAL; + + /* Slurp in the user data */ + if (copy_from_user(kbuf, buf, count)) + return -EFAULT; + kbuf[count] = '\0'; /* * The userns_state_mutex serializes all writes to any given map. @@ -645,17 +654,6 @@ static ssize_t map_write(struct file *fi if (!page) goto out; - /* Only allow < page size writes at the beginning of the file */ - ret = -EINVAL; - if ((*ppos != 0) || (count >= PAGE_SIZE)) - goto out; - - /* Slurp in the user data */ - ret = -EFAULT; - if (copy_from_user(kbuf, buf, count)) - goto out; - kbuf[count] = '\0'; - /* Parse the user data */ ret = -EINVAL; pos = kbuf;