ipv6: fix memory leaks on IPV6_ADDRFORM path

IPV6_ADDRFORM causes resource leaks when converting an IPv6 socket
to IPv4, particularly struct ipv6_ac_socklist. Similar to
struct ipv6_mc_socklist, we should just close it on this path.

This bug can be easily reproduced with the following C program:

  #include <stdio.h>
  #include <string.h>
  #include <sys/types.h>
  #include <sys/socket.h>
  #include <arpa/inet.h>

  int main()
  {
    int s, value;
    struct sockaddr_in6 addr;
    struct ipv6_mreq m6;

    s = socket(AF_INET6, SOCK_DGRAM, 0);
    addr.sin6_family = AF_INET6;
    addr.sin6_port = htons(5000);
    inet_pton(AF_INET6, "::ffff:192.168.122.194", &addr.sin6_addr);
    connect(s, (struct sockaddr *)&addr, sizeof(addr));

    inet_pton(AF_INET6, "fe80::AAAA", &m6.ipv6mr_multiaddr);
    m6.ipv6mr_interface = 5;
    setsockopt(s, SOL_IPV6, IPV6_JOIN_ANYCAST, &m6, sizeof(m6));

    value = AF_INET;
    setsockopt(s, SOL_IPV6, IPV6_ADDRFORM, &value, sizeof(value));

    close(s);
    return 0;
  }

Reported-by: ch3332xr@gmail.com
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/addrconf.h

@@ -274,6 +274,7 @@ int ipv6_sock_ac_join(struct sock *sk, int ifindex,
 		      const struct in6_addr *addr);
 int ipv6_sock_ac_drop(struct sock *sk, int ifindex,
 		      const struct in6_addr *addr);
+void __ipv6_sock_ac_close(struct sock *sk);
 void ipv6_sock_ac_close(struct sock *sk);
 
 int __ipv6_dev_ac_inc(struct inet6_dev *idev, const struct in6_addr *addr);

net/ipv6/anycast.c

@@ -183,7 +183,7 @@ int ipv6_sock_ac_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
 	return 0;
 }
 
-void ipv6_sock_ac_close(struct sock *sk)
+void __ipv6_sock_ac_close(struct sock *sk)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct net_device *dev = NULL;
@@ -191,10 +191,7 @@ void ipv6_sock_ac_close(struct sock *sk)
 	struct net *net = sock_net(sk);
 	int	prev_index;
 
-	if (!np->ipv6_ac_list)
-		return;
-
-	rtnl_lock();
+	ASSERT_RTNL();
 	pac = np->ipv6_ac_list;
 	np->ipv6_ac_list = NULL;
 
@@ -211,6 +208,16 @@ void ipv6_sock_ac_close(struct sock *sk)
 		sock_kfree_s(sk, pac, sizeof(*pac));
 		pac = next;
 	}
+}
+
+void ipv6_sock_ac_close(struct sock *sk)
+{
+	struct ipv6_pinfo *np = inet6_sk(sk);
+
+	if (!np->ipv6_ac_list)
+		return;
+	rtnl_lock();
+	__ipv6_sock_ac_close(sk);
 	rtnl_unlock();
 }
 

net/ipv6/ipv6_sockglue.c

@@ -240,6 +240,7 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 
 			fl6_free_socklist(sk);
 			__ipv6_sock_mc_close(sk);
+			__ipv6_sock_ac_close(sk);
 
 			/*
 			 * Sock is moving from IPv6 to IPv4 (sk_prot), so