Pull keyrings fixes from David Howells:
(1) Disallow keyrings whose name begins with a '.' to be joined
[CVE-2016-9604].
(2) Change the name of the dead type to ".dead" to prevent user access
[CVE-2017-6951].
(3) Fix keyctl_set_reqkey_keyring() to not leak thread keyrings
[CVE-2017-7472]
* tag 'keys-fixes-
20170419' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
KEYS: fix keyctl_set_reqkey_keyring() to not leak thread keyrings
KEYS: Change the name of the dead type to ".dead" to prevent user access
KEYS: Disallow keyrings beginning with '.' to be joined as session keyrings