[IPV4]: ipip and ip_gre encapsulation bugs

Handling of ipip and ip_gre ICMP error relaying is b0rken; it accesses
8bit field + 3 reserved octets as host-endian 32bit, does comparison,
subtraction and stuffs the result back.  That breaks on big-endian.

Fixed, made endian-clean.

[ Note that this effected code is permanently commented out with
  and ifdef, so this error couldn't actually cause problems for
  anyone. -DaveM ]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 10 deletions

diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index 76ab50b0d6ef..0c4556529228 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -341,7 +341,8 @@ out:
         int code = skb->h.icmph->code;
         int rel_type = 0;
         int rel_code = 0;
-        int rel_info = 0;
+        __be32 rel_info = 0;
+        __u32 n = 0;
         struct sk_buff *skb2;
         struct flowi fl;
         struct rtable *rt;
@@ -354,14 +355,15 @@ out:
         default:
                 return 0;
         case ICMP_PARAMETERPROB:
-                if (skb->h.icmph->un.gateway < hlen)
+                n = ntohl(skb->h.icmph->un.gateway) >> 24;
+                if (n < hlen)
                         return 0;
 
                 /* So... This guy found something strange INSIDE encapsulated
                    packet. Well, he is fool, but what can we do ?
                  */
                 rel_type = ICMP_PARAMETERPROB;
-                rel_info = skb->h.icmph->un.gateway - hlen;
+                rel_info = htonl((n - hlen) << 24);
                 break;
 
         case ICMP_DEST_UNREACH:
@@ -372,13 +374,14 @@ out:
                         return 0;
                 case ICMP_FRAG_NEEDED:
                         /* And it is the only really necessary thing :-) */
-                        rel_info = ntohs(skb->h.icmph->un.frag.mtu);
-                        if (rel_info < hlen+68)
+                        n = ntohs(skb->h.icmph->un.frag.mtu);
+                        if (n < hlen+68)
                                 return 0;
-                        rel_info -= hlen;
+                        n -= hlen;
                         /* BSD 4.2 MORE DOES NOT EXIST IN NATURE. */
-                        if (rel_info > ntohs(eiph->tot_len))
+                        if (n > ntohs(eiph->tot_len))
                                 return 0;
+                        rel_info = htonl(n);
                         break;
                 default:
                         /* All others are translated to HOST_UNREACH.
@@ -440,12 +443,11 @@ out:
 
         /* change mtu on this route */
         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
-                if (rel_info > dst_mtu(skb2->dst)) {
+                if (n > dst_mtu(skb2->dst)) {
                         kfree_skb(skb2);
                         return 0;
                 }
-                skb2->dst->ops->update_pmtu(skb2->dst, rel_info);
-                rel_info = htonl(rel_info);
+                skb2->dst->ops->update_pmtu(skb2->dst, n);
         } else if (type == ICMP_TIME_EXCEEDED) {
                 struct ip_tunnel *t = netdev_priv(skb2->dev);
                 if (t->parms.iph.ttl) {