tree 0addc4233c4e08fc7ca69511761bbd2c7402c1de
parent cc50a07a247e17db76b1f0b0ca06652556e04fa3
author Seth Forshee <seth.forshee@canonical.com> 1443039364 -0500
committer Eric W. Biederman <ebiederm@xmission.com> 1466782831 -0500

fs: Limit file caps to the user namespace of the super block

Capability sets attached to files must be ignored except in the
user namespaces where the mounter is privileged, i.e. s_user_ns
and its descendants. Otherwise a vector exists for gaining
privileges in namespaces where a user is not already privileged.

Add a new helper function, current_in_user_ns(), to test whether a user
namespace is the same as or a descendant of another namespace.
Use this helper to determine whether a file's capability set
should be applied to the caps constructed during exec.

--EWB Replaced in_userns with the simpler current_in_userns.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>