tree 4e7093d4e288238f0514187e87b13738504a21df
parent 5e4a08476b50fa39210fca82e03325cc46b9c235
author Eric W. Biederman <ebiederm@xmission.com> 1355503854 -0800
committer Eric W. Biederman <ebiederm@xmission.com> 1355538986 -0800

userns: Add a more complete capability subset test to commit_creds

When unsharing a user namespace we reduce our credentials to just what
can be done in that user namespace.  This is a subset of the credentials
we previously had.  Teach commit_creds to recognize this is a subset
of the credentials we have had before and don't clear the dumpability flag.

This allows an unprivileged  program to do:
unshare(CLONE_NEWUSER);
fd = open("/proc/self/uid_map", O_RDWR);

Where previously opening the uid_map writable would fail because
the the task had been made non-dumpable.

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