From mboxrd@z Thu Jan 1 00:00:00 1970 From: Seth Forshee Subject: [PATCH v5 3/4] fuse: Restrict allow_other to the superblock's namespace or a descendant Date: Wed, 22 Oct 2014 16:24:19 -0500 Message-ID: <1414013060-137148-4-git-send-email-seth.forshee@canonical.com> References: <1414013060-137148-1-git-send-email-seth.forshee@canonical.com> Cc: "Eric W. Biederman" , "Serge H. Hallyn" , Andy Lutomirski , Michael j Theall , fuse-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Seth Forshee To: Miklos Szeredi Return-path: In-Reply-To: <1414013060-137148-1-git-send-email-seth.forshee@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org 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. Therefore access with allow_other should be restricted to users in the userns as the superblock or a descendant of that namespace. Cc: Eric W. Biederman Cc: Serge H. Hallyn Cc: Andy Lutomirski Signed-off-by: Seth Forshee --- fs/fuse/dir.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 123db1e06c78..b23ec5c1ff18 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1091,8 +1091,14 @@ int fuse_allow_current_process(struct fuse_conn *fc) { const struct cred *cred; - if (fc->flags & FUSE_ALLOW_OTHER) - return 1; + if (fc->flags & FUSE_ALLOW_OTHER) { + struct user_namespace *ns; + for (ns = current_user_ns(); ns; ns = ns->parent) { + if (ns == fc->user_ns) + return 1; + } + return 0; + } cred = current_cred(); if (uid_eq(cred->euid, fc->user_id) && -- 1.9.1