[IPV6] TCPMD5: Fix deleting key operation.

Due to the bug, refcnt for md5sig pool was leaked when
an user try to delete a key if we have more than one key.
In addition to the leakage, we returned incorrect return
result value for userspace.

This fix should close Bug #9418, reported by <ming-baini@163.com>.
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/tcp_ipv6.c

@@ -637,10 +637,6 @@ static int tcp_v6_md5_do_del(struct sock *sk, struct in6_addr *peer)
 				kfree(tp->md5sig_info->keys6);
 				tp->md5sig_info->keys6 = NULL;
 				tp->md5sig_info->alloced6 = 0;
-
-				tcp_free_md5sig_pool();
-
-				return 0;
 			} else {
 				/* shrink the database */
 				if (tp->md5sig_info->entries6 != i)
@@ -649,6 +645,8 @@ static int tcp_v6_md5_do_del(struct sock *sk, struct in6_addr *peer)
 						(tp->md5sig_info->entries6 - i)
 						* sizeof (tp->md5sig_info->keys6[0]));
 			}
+			tcp_free_md5sig_pool();
+			return 0;
 		}
 	}
 	return -ENOENT;