static struct sctp_association *__sctp_rcv_lookup_harder(struct sk_buff *skb,
				      const union sctp_addr *laddr,
				      struct sctp_transport **transportp)
{
	sctp_chunkhdr_t *ch;

	ch = (sctp_chunkhdr_t *) skb->data;

	/* The code below will attempt to walk the chunk and extract
	 * parameter information.  Before we do that, we need to verify
	 * that the chunk length doesn't cause overflow.  Otherwise, we'll
	 * walk off the end.
	 */
	if (WORD_ROUND(ntohs(ch->length)) > skb->len)
		return NULL;

	/* If this is INIT/INIT-ACK look inside the chunk too. */
	switch (ch->type) {
	case SCTP_CID_INIT:
	case SCTP_CID_INIT_ACK:
		return __sctp_rcv_init_lookup(skb, laddr, transportp);
		break;

	default:
		return __sctp_rcv_walk_lookup(skb, laddr, transportp);
		break;
	}


	return NULL;
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.