net/netfilter/ipvs: Eliminate memory leak

__ip_vs_service_get and __ip_vs_svc_fwm_get increment a reference count, so
that reference count should be decremented before leaving the function in an
error case.

A simplified version of the semantic match that finds this problem is:
(http://coccinelle.lip6.fr/)

// <smpl>
@r exists@
local idexpression x;
expression E;
identifier f1;
iterator I;
@@

x = __ip_vs_service_get(...);
<... when != x
     when != true (x == NULL || ...)
     when != if (...) { <+...x...+> }
     when != I (...) { <+...x...+> }
(
 x == NULL
|
 x == E
|
 x->f1
)
...>
* return ...;
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NSimon Horman <horms@verge.net.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/netfilter/ipvs/ip_vs_ctl.c

@@ -2155,7 +2155,7 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
 	if (cmd != IP_VS_SO_SET_ADD
 	    && (svc == NULL || svc->protocol != usvc.protocol)) {
 		ret = -ESRCH;
-		goto out_unlock;
+		goto out_drop_service;
 	}
 
 	switch (cmd) {
@@ -2189,6 +2189,7 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
 		ret = -EINVAL;
 	}
 
+out_drop_service:
 	if (svc)
 		ip_vs_service_put(svc);