From patchwork Wed Feb 21 20:29:08 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 10233923 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 53E4C60392 for ; Wed, 21 Feb 2018 20:31:26 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 466F5284D4 for ; Wed, 21 Feb 2018 20:31:26 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3B060284E4; Wed, 21 Feb 2018 20:31:26 +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=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id AAC12284D4 for ; Wed, 21 Feb 2018 20:31:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751168AbeBUUbM (ORCPT ); Wed, 21 Feb 2018 15:31:12 -0500 Received: from out01.mta.xmission.com ([166.70.13.231]:51773 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751407AbeBUUbA (ORCPT ); Wed, 21 Feb 2018 15:31:00 -0500 Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1eob2Z-00005f-GW; Wed, 21 Feb 2018 13:30:59 -0700 Received: from 174-19-85-160.omah.qwest.net ([174.19.85.160] helo=x220.int.ebiederm.org) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1eob2Y-0004Av-UT; Wed, 21 Feb 2018 13:30:59 -0700 From: "Eric W. Biederman" To: Miklos Szeredi Cc: linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, Alban Crequy , Seth Forshee , Sargun Dhillon , Dongsu Park , "Serge E. Hallyn" , "Eric W. Biederman" Date: Wed, 21 Feb 2018 14:29:08 -0600 Message-Id: <20180221202908.17258-5-ebiederm@xmission.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <878tbmf5vl.fsf@xmission.com> References: <878tbmf5vl.fsf@xmission.com> X-XM-SPF: eid=1eob2Y-0004Av-UT; ; ; mid=<20180221202908.17258-5-ebiederm@xmission.com>; ; ; hst=in02.mta.xmission.com; ; ; ip=174.19.85.160; ; ; frm=ebiederm@xmission.com; ; ; spf=neutral X-XM-AID: U2FsdGVkX19mzDCCaskvtQtga3PZFjdPcHZ77wZGT+A= X-SA-Exim-Connect-IP: 174.19.85.160 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH v6 5/5] fuse: Restrict allow_other to the superblock's namespace or a descendant X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Seth Forshee Unprivileged users are normally restricted from mounting with the allow_other option by system policy, but this could be bypassed for a mount done with user namespace root permissions. In such cases allow_other should not allow users outside the userns to access the mount as doing so would give the unprivileged user the ability to manipulate processes it would otherwise be unable to manipulate. Restrict allow_other to apply to users in the same userns used at mount or a descendant of that namespace. Also export current_in_userns() for use by fuse when built as a module. Cc: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: "Eric W. Biederman" Cc: Serge Hallyn Cc: Miklos Szeredi Acked-by: Miklos Szeredi Reviewed-by: Serge Hallyn Reviewed-by: "Eric W. Biederman" Signed-off-by: Seth Forshee Signed-off-by: Dongsu Park Signed-off-by: Eric W. Biederman --- fs/fuse/dir.c | 2 +- kernel/user_namespace.c | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index ad1cfac1942f..d41559a0aa6b 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1030,7 +1030,7 @@ int fuse_allow_current_process(struct fuse_conn *fc) const struct cred *cred; if (fc->allow_other) - return 1; + return current_in_userns(fc->user_ns); cred = current_cred(); if (uid_eq(cred->euid, fc->user_id) && diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 246d4d4ce5c7..492c255e6c5a 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -1235,6 +1235,7 @@ bool current_in_userns(const struct user_namespace *target_ns) { return in_userns(target_ns, current_user_ns()); } +EXPORT_SYMBOL(current_in_userns); static inline struct user_namespace *to_user_ns(struct ns_common *ns) {