net/sched: fix memory leak in act_tunnel_key_init()

If users try to install act_tunnel_key 'set' rules with duplicate values
of 'index', the tunnel metadata are allocated, but never released. Then,
kmemleak complains as follows:

 # tc a a a tunnel_key set src_ip 1.1.1.1 dst_ip 2.2.2.2 id 42 index 111
 # echo clear > /sys/kernel/debug/kmemleak
 # tc a a a tunnel_key set src_ip 1.1.1.1 dst_ip 2.2.2.2 id 42 index 111
 Error: TC IDR already exists.
 We have an error talking to the kernel
 # echo scan > /sys/kernel/debug/kmemleak
 # cat /sys/kernel/debug/kmemleak
 unreferenced object 0xffff8800574e6c80 (size 256):
   comm "tc", pid 5617, jiffies 4298118009 (age 57.990s)
   hex dump (first 32 bytes):
     00 00 00 00 00 00 00 00 00 1c e8 b0 ff ff ff ff  ................
     81 24 c2 ad ff ff ff ff 00 00 00 00 00 00 00 00  .$..............
   backtrace:
     [<00000000b7afbf4e>] tunnel_key_init+0x8a5/0x1800 [act_tunnel_key]
     [<000000007d98fccd>] tcf_action_init_1+0x698/0xac0
     [<0000000099b8f7cc>] tcf_action_init+0x15c/0x590
     [<00000000dc60eebe>] tc_ctl_action+0x336/0x5c2
     [<000000002f5a2f7d>] rtnetlink_rcv_msg+0x357/0x8e0
     [<000000000bfe7575>] netlink_rcv_skb+0x124/0x350
     [<00000000edab656f>] netlink_unicast+0x40f/0x5d0
     [<00000000b322cdcb>] netlink_sendmsg+0x6e8/0xba0
     [<0000000063d9d490>] sock_sendmsg+0xb3/0xf0
     [<00000000f0d3315a>] ___sys_sendmsg+0x654/0x960
     [<00000000c06cbd42>] __sys_sendmsg+0xd3/0x170
     [<00000000ce72e4b0>] do_syscall_64+0xa5/0x470
     [<000000005caa2d97>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
     [<00000000fac1b476>] 0xffffffffffffffff

This problem theoretically happens also in case users attempt to setup a
geneve rule having wrong configuration data, or when the kernel fails to
allocate 'params_new'. Ensure that tunnel_key_init() releases the tunnel
metadata also in the above conditions.

Addresses-Coverity-ID: 1373974 ("Resource leak")
Fixes: d0f6dd8a ("net/sched: Introduce act_tunnel_key")
Fixes: 0ed5269f ("net/sched: add tunnel option support to act_tunnel_key")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_tunnel_key.c

@@ -317,7 +317,7 @@ static int tunnel_key_init(struct net *net, struct nlattr *nla,
 						  &metadata->u.tun_info,
 						  opts_len, extack);
 			if (ret < 0)
-				goto err_out;
+				goto release_tun_meta;
 		}
 
 		metadata->u.tun_info.mode |= IP_TUNNEL_INFO_TX;
@@ -333,23 +333,24 @@ static int tunnel_key_init(struct net *net, struct nlattr *nla,
 				     &act_tunnel_key_ops, bind, true);
 		if (ret) {
 			NL_SET_ERR_MSG(extack, "Cannot create TC IDR");
-			goto err_out;
+			goto release_tun_meta;
 		}
 
 		ret = ACT_P_CREATED;
 	} else if (!ovr) {
-		tcf_idr_release(*a, bind);
 		NL_SET_ERR_MSG(extack, "TC IDR already exists");
-		return -EEXIST;
+		ret = -EEXIST;
+		goto release_tun_meta;
 	}
 
 	t = to_tunnel_key(*a);
 
 	params_new = kzalloc(sizeof(*params_new), GFP_KERNEL);
 	if (unlikely(!params_new)) {
-		tcf_idr_release(*a, bind);
 		NL_SET_ERR_MSG(extack, "Cannot allocate tunnel key parameters");
-		return -ENOMEM;
+		ret = -ENOMEM;
+		exists = true;
+		goto release_tun_meta;
 	}
 	params_new->tcft_action = parm->t_action;
 	params_new->tcft_enc_metadata = metadata;
@@ -367,6 +368,9 @@ static int tunnel_key_init(struct net *net, struct nlattr *nla,
 
 	return ret;
 
+release_tun_meta:
+	dst_release(&metadata->dst);
+
 err_out:
 	if (exists)
 		tcf_idr_release(*a, bind);