ipv4: udp: fix short packet and bad checksum logging

commit 2783ef23 moved the initialisation of saddr and daddr after
pskb_may_pull() to avoid a potential data corruption.  Unfortunately
also placing it after the short packet and bad checksum error paths,
where these variables are used for logging.  The result is bogus
output like

[92238.389505] UDP: short packet: From 2.0.0.0:65535 23715/178 to 0.0.0.0:65535

Moving the saddr and daddr initialisation above the error paths, while still
keeping it after the pskb_may_pull() to keep the fix from commit 2783ef23.
Signed-off-by: NBjørn Mork <bjorn@mork.no>
Cc: stable@kernel.org
Acked-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/udp.c

@@ -1527,6 +1527,9 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 
 	uh   = udp_hdr(skb);
 	ulen = ntohs(uh->len);
+	saddr = ip_hdr(skb)->saddr;
+	daddr = ip_hdr(skb)->daddr;
+
 	if (ulen > skb->len)
 		goto short_packet;
 
@@ -1540,9 +1543,6 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	if (udp4_csum_init(skb, uh, proto))
 		goto csum_error;
 
-	saddr = ip_hdr(skb)->saddr;
-	daddr = ip_hdr(skb)->daddr;
-
 	if (rt->rt_flags & (RTCF_BROADCAST|RTCF_MULTICAST))
 		return __udp4_lib_mcast_deliver(net, skb, uh,
 				saddr, daddr, udptable);