tree 837c44ca6029aae35fa92c3a067fb3d96dcd0f0d
parent 8b70761d058cf87c9dc3f7b962fbf3c79dc61b1c
author Seth Forshee <seth.forshee@canonical.com> 1513953153 +0100
committer Eric W. Biederman <ebiederm@xmission.com> 1519688104 -0600

fuse: Restrict allow_other to the superblock's namespace or a descendant

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" <ebiederm@xmission.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Dongsu Park <dongsu@kinvolk.io>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>