ipv6: Fix 'inet6_rtm_getroute' to release 'rt->dst' in case of 'alloc_skb' failure

In 72331bc0 [ipv6: Fix RTM_GETROUTE's interpretation of RTA_IIF to be
consistent with ipv4] the code of 'inet6_rtm_getroute()' was re-ordered
such that the reference to 'rt->dst' is incremented prior skb
allocation.

Hence, if 'alloc_skb()' fails, must drop a reference from 'rt->dst'.
Add the missing 'dst_release()' call.
Signed-off-by: NShmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/route.c

@@ -2606,6 +2606,7 @@ static int inet6_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr* nlh, void
 
 	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
 	if (!skb) {
+		dst_release(&rt->dst);
 		err = -ENOBUFS;
 		goto errout;
 	}