ipv6: Fix NULL pointer dereference with time-wait sockets

Commit b2f5e7cd
(ipv6: Fix conflict resolutions during ipv6 binding)
introduced a regression where time-wait sockets were
not treated correctly.  This resulted in the following:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000062
IP: [<ffffffff805d7d61>] ipv4_rcv_saddr_equal+0x61/0x70
...
Call Trace:
[<ffffffffa033847b>] ipv6_rcv_saddr_equal+0x1bb/0x250 [ipv6]
[<ffffffffa03505a8>] inet6_csk_bind_conflict+0x88/0xd0 [ipv6]
[<ffffffff805bb18e>] inet_csk_get_port+0x1ee/0x400
[<ffffffffa0319b7f>] inet6_bind+0x1cf/0x3a0 [ipv6]
[<ffffffff8056d17c>] ? sockfd_lookup_light+0x3c/0xd0
[<ffffffff8056ed49>] sys_bind+0x89/0x100
[<ffffffff80613ea2>] ? trace_hardirqs_on_thunk+0x3a/0x3c
[<ffffffff8020bf9b>] system_call_fastpath+0x16/0x1b
Tested-by: NBrian Haley <brian.haley@hp.com>
Tested-by: NEd Tomlinson <edt@aei.ca>
Signed-off-by: NVlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/udp.h

@@ -124,8 +124,6 @@ static inline void udp_lib_close(struct sock *sk, long timeout)
 	sk_common_release(sk);
 }
 
-extern int	ipv4_rcv_saddr_equal(const struct sock *sk1,
-				    const struct sock *sk2);
 extern int	udp_lib_get_port(struct sock *sk, unsigned short snum,
 		int (*)(const struct sock*,const struct sock*));
 

net/ipv4/udp.c

@@ -222,7 +222,7 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
 	return error;
 }
 
-int ipv4_rcv_saddr_equal(const struct sock *sk1, const struct sock *sk2)
+static int ipv4_rcv_saddr_equal(const struct sock *sk1, const struct sock *sk2)
 {
 	struct inet_sock *inet1 = inet_sk(sk1), *inet2 = inet_sk(sk2);
 
@@ -1823,7 +1823,6 @@ EXPORT_SYMBOL(udp_lib_getsockopt);
 EXPORT_SYMBOL(udp_lib_setsockopt);
 EXPORT_SYMBOL(udp_poll);
 EXPORT_SYMBOL(udp_lib_get_port);
-EXPORT_SYMBOL(ipv4_rcv_saddr_equal);
 
 #ifdef CONFIG_PROC_FS
 EXPORT_SYMBOL(udp_proc_register);

net/ipv6/udp.c

@@ -53,6 +53,8 @@ int ipv6_rcv_saddr_equal(const struct sock *sk, const struct sock *sk2)
 {
 	const struct in6_addr *sk_rcv_saddr6 = &inet6_sk(sk)->rcv_saddr;
 	const struct in6_addr *sk2_rcv_saddr6 = inet6_rcv_saddr(sk2);
+	__be32 sk_rcv_saddr = inet_sk(sk)->rcv_saddr;
+	__be32 sk2_rcv_saddr = inet_rcv_saddr(sk2);
 	int sk_ipv6only = ipv6_only_sock(sk);
 	int sk2_ipv6only = inet_v6_ipv6only(sk2);
 	int addr_type = ipv6_addr_type(sk_rcv_saddr6);
@@ -60,7 +62,9 @@ int ipv6_rcv_saddr_equal(const struct sock *sk, const struct sock *sk2)
 
 	/* if both are mapped, treat as IPv4 */
 	if (addr_type == IPV6_ADDR_MAPPED && addr_type2 == IPV6_ADDR_MAPPED)
-		return ipv4_rcv_saddr_equal(sk, sk2);
+		return (!sk2_ipv6only &&
+			(!sk_rcv_saddr || !sk2_rcv_saddr ||
+			  sk_rcv_saddr == sk2_rcv_saddr));
 
 	if (addr_type2 == IPV6_ADDR_ANY &&
 	    !(sk2_ipv6only && addr_type == IPV6_ADDR_MAPPED))