udplite: fix NULL pointer dereference

The commit 850cbad ("udp: use it's own memory accounting schema")
assumes that the socket proto has memory accounting enabled,
but this is not the case for UDPLITE.
Fix it enabling memory accounting for UDPLITE and performing
fwd allocated memory reclaiming on socket shutdown.
UDP and UDPLITE share now the same memory accounting limits.
Also drop the backlog receive operation, since is no more needed.

Fixes: 850cbad ("udp: use it's own memory accounting schema")
Reported-by: Andrei Vagin <avagin@gmail.com>
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Paolo Abeni

include/net/udp.h

@@ -246,6 +246,7 @@ static inline __be16 udp_flow_src_port(struct net *net, struct sk_buff *skb,
 }
 
 /* net/ipv4/udp.c */
+void udp_destruct_sock(struct sock *sk);
 void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len);
 int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb);
 void udp_skb_destructor(struct sock *sk, struct sk_buff *skb);

include/net/udplite.h

@@ -27,6 +27,7 @@ static __inline__ int udplite_getfrag(void *from, char *to, int  offset,
 static inline int udplite_sk_init(struct sock *sk)
 {
 	udp_sk(sk)->pcflag = UDPLITE_BIT;
+	sk->sk_destruct = udp_destruct_sock;
 	return 0;
 }
 

net/ipv4/udp.c

@@ -1253,7 +1253,7 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
 }
 EXPORT_SYMBOL_GPL(__udp_enqueue_schedule_skb);
 
-static void udp_destruct_sock(struct sock *sk)
+void udp_destruct_sock(struct sock *sk)
 {
 	/* reclaim completely the forward allocated memory */
 	unsigned int total = 0;
@@ -1267,6 +1267,7 @@ static void udp_destruct_sock(struct sock *sk)
 
 	inet_sock_destruct(sk);
 }
+EXPORT_SYMBOL_GPL(udp_destruct_sock);
 
 int udp_init_sock(struct sock *sk)
 {

net/ipv4/udplite.c

@@ -50,10 +50,11 @@ struct proto 	udplite_prot = {
 	.sendmsg	   = udp_sendmsg,
 	.recvmsg	   = udp_recvmsg,
 	.sendpage	   = udp_sendpage,
-	.backlog_rcv	   = udp_queue_rcv_skb,
 	.hash		   = udp_lib_hash,
 	.unhash		   = udp_lib_unhash,
 	.get_port	   = udp_v4_get_port,
+	.memory_allocated  = &udp_memory_allocated,
+	.sysctl_mem	   = sysctl_udp_mem,
 	.obj_size	   = sizeof(struct udp_sock),
 	.h.udp_table	   = &udplite_table,
 #ifdef CONFIG_COMPAT

net/ipv6/udplite.c

@@ -45,10 +45,11 @@ struct proto udplitev6_prot = {
 	.getsockopt	   = udpv6_getsockopt,
 	.sendmsg	   = udpv6_sendmsg,
 	.recvmsg	   = udpv6_recvmsg,
-	.backlog_rcv	   = udpv6_queue_rcv_skb,
 	.hash		   = udp_lib_hash,
 	.unhash		   = udp_lib_unhash,
 	.get_port	   = udp_v6_get_port,
+	.memory_allocated  = &udp_memory_allocated,
+	.sysctl_mem	   = sysctl_udp_mem,
 	.obj_size	   = sizeof(struct udp6_sock),
 	.h.udp_table	   = &udplite_table,
 #ifdef CONFIG_COMPAT