[TCP]: Use get_unaligned() in tcp_parse_options()

TCP options are not guaranteed to be aligned at all, so we should use
get_unaligned when accessing u16- or u32-values in the TCP
options header to avoid alignment errors on some platforms. The patch
applies to vanilla 2.6.11.
Signed-off-by: Sven Henkel <shenkel@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

@@ -71,6 +71,7 @@
 #include <net/tcp.h>
 #include <net/inet_common.h>
 #include <linux/ipsec.h>
+#include <asm/unaligned.h>
 
 int sysctl_tcp_timestamps = 1;
 int sysctl_tcp_window_scaling = 1;
@@ -3007,7 +3008,7 @@ void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx,
 	  			switch(opcode) {
 				case TCPOPT_MSS:
 					if(opsize==TCPOLEN_MSS && th->syn && !estab) {
-						u16 in_mss = ntohs(*(__u16 *)ptr);
+						u16 in_mss = ntohs(get_unaligned((__u16 *)ptr));
 						if (in_mss) {
 							if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
 								in_mss = opt_rx->user_mss;
@@ -3034,8 +3035,8 @@ void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx,
 						if ((estab && opt_rx->tstamp_ok) ||
 						    (!estab && sysctl_tcp_timestamps)) {
 							opt_rx->saw_tstamp = 1;
-							opt_rx->rcv_tsval = ntohl(*(__u32 *)ptr);
-							opt_rx->rcv_tsecr = ntohl(*(__u32 *)(ptr+4));
+							opt_rx->rcv_tsval = ntohl(get_unaligned((__u32 *)ptr));
+							opt_rx->rcv_tsecr = ntohl(get_unaligned((__u32 *)(ptr+4)));
 						}
 					}
 					break;