tipc: fix a possible memory leak

The commit a8b9b96e ("tipc: fix race
in disc create/delete") leads to the following static checker warning:

	net/tipc/discover.c:352 tipc_disc_create()
		warn: possible memory leak of 'req'

The risk of memory leak really exists in practice. Especially when
it's failed to allocate memory for "req->buf", tipc_disc_create()
doesn't free its allocated memory, instead just directly returns
with ENOMEM error code. In this situation, memory leak, of course,
happens.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NYing Xue <ying.xue@windriver.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/tipc/discover.c

@@ -348,8 +348,10 @@ int tipc_disc_create(struct tipc_bearer *b_ptr, struct tipc_media_addr *dest)
 		return -ENOMEM;
 
 	req->buf = tipc_buf_acquire(INT_H_SIZE);
-	if (!req->buf)
+	if (!req->buf) {
+		kfree(req);
 		return -ENOMEM;
+	}
 
 	tipc_disc_init_msg(req->buf, DSC_REQ_MSG, b_ptr);
 	memcpy(&req->dest, dest, sizeof(*dest));