smack: fix key permission verification

For any keyring access type SMACK always used MAY_READWRITE access check.
It prevents reading the key with label "_", which should be allowed for anyone.

This patch changes default access check to MAY_READ and use MAY_READWRITE in only
appropriate cases.

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
1 file changed