security/keys: export key_lookup()

For in-kernel consumers one cannot readily assign a user (eg when
running from a workqueue), so the normal key search permissions
cannot be applied.
This patch exports the 'key_lookup()' function for a simple lookup
of keys without checking for permissions.

Signed-off-by: Hannes Reinecke <[e-mail]>
Reviewed-by: Sagi Grimberg <[e-mail]>
Acked-by: David Howells <[e-mail]>
Signed-off-by: Keith Busch <[e-mail]>

include/linux/key.h

···
 #define key_init()			do { } while(0)
 #define key_free_user_ns(ns)		do { } while(0)
 #define key_remove_domain(d)		do { } while(0)
+#define key_lookup(k)			NULL
 
 #endif /* CONFIG_KEYS */
 #endif /* __KERNEL__ */

security/keys/key.c

···
 	spin_unlock(&key_serial_lock);
 	return key;
 }
+EXPORT_SYMBOL(key_lookup);
 
 /*
  * Find and lock the specified key type against removal.