keys: Timestamp new keys

Set the timestamp on new keys rather than leaving it unset.

Fixes: 31d5a79d ("KEYS: Do LRU discard in full keyrings")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.morris@microsoft.com>

security/keys/key.c

@@ -297,6 +297,7 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 	key->gid = gid;
 	key->perm = perm;
 	key->restrict_link = restrict_link;
+	key->last_used_at = ktime_get_real_seconds();
 
 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
 		key->flags |= 1 << KEY_FLAG_IN_QUOTA;