net/smc: fix neighbour and rtable leak in smc_ib_find_route()

In smc_ib_find_route(), the neighbour found by neigh_lookup() and rtable
resolved by ip_route_output_flow() are not released or put before return.
It may cause the refcount leak, so fix it.

Link: https://lore.kernel.org/r/20240506015439.108739-1-guwen@linux.alibaba.com
Fixes: e5c4744 ("net/smc: add SMC-Rv2 connection establishment")
Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240507125331.2808-1-guwen@linux.alibaba.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: Wen Gu

net/smc/smc_ib.c

@@ -209,13 +209,18 @@ int smc_ib_find_route(struct net *net, __be32 saddr, __be32 daddr,
 	if (IS_ERR(rt))
 		goto out;
 	if (rt->rt_uses_gateway && rt->rt_gw_family != AF_INET)
-		goto out;
-	neigh = rt->dst.ops->neigh_lookup(&rt->dst, NULL, &fl4.daddr);
-	if (neigh) {
-		memcpy(nexthop_mac, neigh->ha, ETH_ALEN);
-		*uses_gateway = rt->rt_uses_gateway;
-		return 0;
-	}
+		goto out_rt;
+	neigh = dst_neigh_lookup(&rt->dst, &fl4.daddr);
+	if (!neigh)
+		goto out_rt;
+	memcpy(nexthop_mac, neigh->ha, ETH_ALEN);
+	*uses_gateway = rt->rt_uses_gateway;
+	neigh_release(neigh);
+	ip_rt_put(rt);
+	return 0;
+
+out_rt:
+	ip_rt_put(rt);
 out:
 	return -ENOENT;
 }