RDMA/i40iw: Fix potential use after free

[ Upstream commit da046d5f ]

Release variable dst after logging dst->error to avoid possible use after
free.

Link: https://lore.kernel.org/r/1573022651-37171-1-git-send-email-bianpan2016@163.comSigned-off-by: NPan Bian <bianpan2016@163.com>
Reviewed-by: NJason Gunthorpe <jgg@mellanox.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/infiniband/hw/i40iw/i40iw_cm.c

@@ -2071,9 +2071,9 @@ static int i40iw_addr_resolve_neigh_ipv6(struct i40iw_device *iwdev,
 	dst = i40iw_get_dst_ipv6(&src_addr, &dst_addr);
 	if (!dst || dst->error) {
 		if (dst) {
-			dst_release(dst);
 			i40iw_pr_err("ip6_route_output returned dst->error = %d\n",
 				     dst->error);
+			dst_release(dst);
 		}
 		return rc;
 	}