netfilter: nf_conntrack_tcp: fix unaligned memory access in tcp_sack

This patch fixes an unaligned memory access in tcp_sack while reading
sequence numbers from TCP selective acknowledgement options.  Prior to
applying this patch, upstream linux-2.6.27.20 was occasionally
generating messages like this on my sparc64 system:

  [54678.532071] Kernel unaligned access at TPC[6b17d4] tcp_packet+0xcd4/0xd00

Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index f3fd154d1ddd..56ac4ee77a1d 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -15,6 +15,7 @@
 #include <linux/skbuff.h>
 #include <linux/ipv6.h>
 #include <net/ip6_checksum.h>
+#include <asm/unaligned.h>
 
 #include <net/tcp.h>
 
@@ -466,7 +467,7 @@ static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff,
                                 for (i = 0;
                                      i < (opsize - TCPOLEN_SACK_BASE);
                                      i += TCPOLEN_SACK_PERBLOCK) {
-                                        tmp = ntohl(*((__be32 *)(ptr+i)+1));
+                                        tmp = get_unaligned_be32((__be32 *)(ptr+i)+1);
 
                                         if (after(tmp, *sack))
                                                 *sack = tmp;