From patchwork Fri Mar 2 21:59:19 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: 10255785 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 862866037F for ; Fri, 2 Mar 2018 22:02:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 724EF281E1 for ; Fri, 2 Mar 2018 22:02:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6733B283F5; Fri, 2 Mar 2018 22:02:32 +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=ham 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 504E2281E1 for ; Fri, 2 Mar 2018 22:02:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933248AbeCBWC3 (ORCPT ); Fri, 2 Mar 2018 17:02:29 -0500 Received: from out03.mta.xmission.com ([166.70.13.233]:39297 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932815AbeCBWBA (ORCPT ); Fri, 2 Mar 2018 17:01:00 -0500 Received: from in02.mta.xmission.com ([166.70.13.52]) by out03.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1ersjb-0008Km-9R; Fri, 02 Mar 2018 15:00:59 -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 1ersjZ-0000ts-NM; Fri, 02 Mar 2018 15:00:59 -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" , Linus Torvalds , "Eric W. Biederman" Date: Fri, 2 Mar 2018 15:59:19 -0600 Message-Id: <20180302215919.27207-6-ebiederm@xmission.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <87r2p287i8.fsf_-_@xmission.com> References: <87r2p287i8.fsf_-_@xmission.com> X-XM-SPF: eid=1ersjZ-0000ts-NM; ; ; mid=<20180302215919.27207-6-ebiederm@xmission.com>; ; ; hst=in02.mta.xmission.com; ; ; ip=174.19.85.160; ; ; frm=ebiederm@xmission.com; ; ; spf=neutral X-XM-AID: U2FsdGVkX196h5zsM4VeLBTVW4lH/rhDzbWOfpJ+gaY= X-SA-Exim-Connect-IP: 174.19.85.160 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH v8 6/6] 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 c749a4bd4ea3..5461b63bb2a4 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) {