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Eric W. Biederman authored
commit 273d2c67 upstream. setgroups is unique in not needing a valid mapping before it can be called, in the case of setgroups(0, NULL) which drops all supplemental groups. The design of the user namespace assumes that CAP_SETGID can not actually be used until a gid mapping is established. Therefore add a helper function to see if the user namespace gid mapping has been established and call that function in the setgroups permission check. This is part of the fix for CVE-2014-8989, being able to drop groups without privilege using user namespaces. Reviewed-by:
Andy Lutomirski <luto@amacapital.net> Signed-off-by:
"Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by:
Luis Henriques <luis.henriques@canonical.com>
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