security/keys: export key_lookup()

JIRA: https://issues.redhat.com/browse/RHEL-25547

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 <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
(cherry picked from commit 037c343)
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>

Author: maurizio-lombardi

include/linux/key.h

@@ -510,6 +510,7 @@ extern void key_init(void);
 #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

@@ -690,6 +690,7 @@ struct key *key_lookup(key_serial_t id)
 	spin_unlock(&key_serial_lock);
 	return key;
 }
+EXPORT_SYMBOL(key_lookup);
 
 /*
  * Find and lock the specified key type against removal.