static void request_key_auth_revoke(struct key *key)
{
	struct request_key_auth *rka = key->payload.data;

	kenter("{%d}", key->serial);

	if (rka->cred) {
		put_cred(rka->cred);
		rka->cred = NULL;
	}
}

The product dereferences a pointer that it expects to be valid but is NULL.