Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753078AbcDZThy (ORCPT ); Tue, 26 Apr 2016 15:37:54 -0400 Received: from mail-ig0-f173.google.com ([209.85.213.173]:36282 "EHLO mail-ig0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753080AbcDZTh2 (ORCPT ); Tue, 26 Apr 2016 15:37:28 -0400 From: Seth Forshee To: "Eric W. Biederman" , Miklos Szeredi Cc: Alexander Viro , Serge Hallyn , Richard Weinberger , Austin S Hemmelgarn , Miklos Szeredi , Pavel Tikhomirov , linux-kernel@vger.kernel.org, linux-bcache@vger.kernel.org, dm-devel@redhat.com, linux-raid@vger.kernel.org, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, fuse-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov, cgroups@vger.kernel.org, Seth Forshee Subject: [PATCH v4 20/21] fuse: Restrict allow_other to the superblock's namespace or a descendant Date: Tue, 26 Apr 2016 14:36:33 -0500 Message-Id: <1461699396-33000-21-git-send-email-seth.forshee@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1461699396-33000-1-git-send-email-seth.forshee@canonical.com> References: <1461699396-33000-1-git-send-email-seth.forshee@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1627 Lines: 46 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. Signed-off-by: Seth Forshee Acked-by: Serge Hallyn Acked-by: Miklos Szeredi --- 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 ecba75bf6640..1a6c5af49608 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1015,7 +1015,7 @@ int fuse_allow_current_process(struct fuse_conn *fc) const struct cred *cred; if (fc->flags & FUSE_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 68f594212759..fa2294e14b77 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -951,6 +951,7 @@ bool current_in_userns(const struct user_namespace *target_ns) } return false; } +EXPORT_SYMBOL(current_in_userns); static inline struct user_namespace *to_user_ns(struct ns_common *ns) { -- 2.7.4