udplite: call proper backlog handlers

In commits 93821778def10 ("udp: Fix rcv socket locking") and
f7ad74fef3af ("net/ipv6/udp: UDP encapsulation: break backlog_rcv into
__udpv6_queue_rcv_skb") UDP backlog handlers were renamed, but UDPlite
was forgotten.

This leads to crashes if UDPlite header is pulled twice, which happens
starting from commit e6afc8ace6dd ("udp: remove headers from UDP packets
before queueing")

Bug found by syzkaller team, thanks a lot guys !

Note that backlog use in UDP/UDPlite is scheduled to be removed starting
from linux-4.10, so this patch is only needed up to linux-4.9

Fixes: 93821778def1 ("udp: Fix rcv socket locking")
Fixes: f7ad74fef3af ("net/ipv6/udp: UDP encapsulation: break backlog_rcv into __udpv6_queue_rcv_skb")
Fixes: e6afc8ace6dd ("udp: remove headers from UDP packets before queueing")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp_impl.h b/net/ipv4/udp_impl.h
index 7e0fe4b..feb50a1 100644
--- a/net/ipv4/udp_impl.h
+++ b/net/ipv4/udp_impl.h
@@ -25,7 +25,7 @@
 		int flags, int *addr_len);
 int udp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
 		 int flags);
-int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
+int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
 void udp_destroy_sock(struct sock *sk);
 
 #ifdef CONFIG_PROC_FS