int mainloop(CLIENT *client) {
	struct nbd_request request;
	struct nbd_reply reply;
	gboolean go_on=TRUE;
#ifdef DODBG
	int i = 0;
#endif
	negotiate(client->net, client, NULL);
	DEBUG("Entering request loop!\n");
	reply.magic = htonl(NBD_REPLY_MAGIC);
	reply.error = 0;
	while (go_on) {
		char buf[BUFSIZE];
		size_t len;
#ifdef DODBG
		i++;
		printf("%d: ", i);
#endif
		readit(client->net, &request, sizeof(request));
		request.from = ntohll(request.from);
		request.type = ntohl(request.type);

		if (request.type==NBD_CMD_DISC) {
			msg2(LOG_INFO, "Disconnect request received.");
                	if (client->server->flags & F_COPYONWRITE) { 
				if (client->difmap) g_free(client->difmap) ;
                		close(client->difffile);
				unlink(client->difffilename);
				free(client->difffilename);
			}
			go_on=FALSE;
			continue;
		}

		len = ntohl(request.len);
 
 		if (request.magic != htonl(NBD_REQUEST_MAGIC))
 			err("Not enough magic.");
		if (len > BUFSIZE + sizeof(struct nbd_reply))
 			err("Request too big!");
 #ifdef DODBG
 		printf("%s from %llu (%llu) len %d, ", request.type ? "WRITE" :
				"READ", (unsigned long long)request.from,
				(unsigned long long)request.from / 512, len);
#endif
		memcpy(reply.handle, request.handle, sizeof(reply.handle));
		if ((request.from + len) > (OFFT_MAX)) {
			DEBUG("[Number too large!]");
			ERROR(client, reply, EINVAL);
			continue;
		}

		if (((ssize_t)((off_t)request.from + len) > client->exportsize)) {
			DEBUG("[RANGE!]");
			ERROR(client, reply, EINVAL);
			continue;
		}

		if (request.type==NBD_CMD_WRITE) {
			DEBUG("wr: net->buf, ");
			readit(client->net, buf, len);
			DEBUG("buf->exp, ");
			if ((client->server->flags & F_READONLY) ||
			    (client->server->flags & F_AUTOREADONLY)) {
				DEBUG("[WRITE to READONLY!]");
				ERROR(client, reply, EPERM);
				continue;
			}
			if (expwrite(request.from, buf, len, client)) {
				DEBUG("Write failed: %m" );
				ERROR(client, reply, errno);
				continue;
			}
			SEND(client->net, reply);
			DEBUG("OK!\n");
			continue;
		}
		/* READ */

		DEBUG("exp->buf, ");
		if (expread(request.from, buf + sizeof(struct nbd_reply), len, client)) {
			DEBUG("Read failed: %m");
			ERROR(client, reply, errno);
			continue;
		}

		DEBUG("buf->net, ");
		memcpy(buf, &reply, sizeof(struct nbd_reply));
		writeit(client->net, buf, len + sizeof(struct nbd_reply));
		DEBUG("OK!\n");
	}
	return 0;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.