ipv6: make fragment identifications less predictable, CVE-2011-2699

[linux-flexiantxendom0-natty.git] / net / ipv6 / ip6_output.c

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 5f8d242..ed0c1a7 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -596,6 +596,35 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
        return offset;
 }
 
+static u32 hashidentrnd __read_mostly;
+#define FID_HASH_SZ 16
+static u32 ipv6_fragmentation_id[FID_HASH_SZ];
+
+void __init initialize_hashidentrnd(void)
+{
+       get_random_bytes(&hashidentrnd, sizeof(hashidentrnd));
+}
+
+static u32 __ipv6_select_ident(const struct in6_addr *addr)
+{
+       u32 newid, oldid, hash = jhash2((u32 *)addr, 4, hashidentrnd);
+       u32 *pid = &ipv6_fragmentation_id[hash % FID_HASH_SZ];
+
+       do {
+               oldid = *pid;
+               newid = oldid + 1;
+               if (!(hash + newid))
+                       newid++;
+       } while (cmpxchg(pid, oldid, newid) != oldid);
+
+       return hash + newid;
+}
+
+void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
+{
+       fhdr->identification = htonl(__ipv6_select_ident(&rt->rt6i_dst.addr));
+}
+
 int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 {
        struct sk_buff *frag;
@@ -680,7 +709,7 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
                skb_reset_network_header(skb);
                memcpy(skb_network_header(skb), tmp_hdr, hlen);
 
-               ipv6_select_ident(fh);
+               ipv6_select_ident(fh, rt);
                fh->nexthdr = nexthdr;
                fh->reserved = 0;
                fh->frag_off = htons(IP6_MF);
@@ -826,7 +855,7 @@ slow_path:
                fh->nexthdr = nexthdr;
                fh->reserved = 0;
                if (!frag_id) {
-                       ipv6_select_ident(fh);
+                       ipv6_select_ident(fh, rt);
                        frag_id = fh->identification;
                } else
                        fh->identification = frag_id;
@@ -1030,7 +1059,8 @@ static inline int ip6_ufo_append_data(struct sock *sk,
                        int getfrag(void *from, char *to, int offset, int len,
                        int odd, struct sk_buff *skb),
                        void *from, int length, int hh_len, int fragheaderlen,
-                       int transhdrlen, int mtu,unsigned int flags)
+                       int transhdrlen, int mtu,unsigned int flags,
+                       struct rt6_info *rt)
 
 {
        struct sk_buff *skb;
@@ -1075,7 +1105,7 @@ static inline int ip6_ufo_append_data(struct sock *sk,
                skb_shinfo(skb)->gso_size = (mtu - fragheaderlen -
                                             sizeof(struct frag_hdr)) & ~7;
                skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
-               ipv6_select_ident(&fhdr);
+               ipv6_select_ident(&fhdr, rt);
                skb_shinfo(skb)->ip6_frag_id = fhdr.identification;
                __skb_queue_tail(&sk->sk_write_queue, skb);
 
@@ -1231,7 +1261,7 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
 
                        err = ip6_ufo_append_data(sk, getfrag, from, length,
                                                  hh_len, fragheaderlen,
-                                                 transhdrlen, mtu, flags);
+                                                 transhdrlen, mtu, flags, rt);
                        if (err)
                                goto error;
                        return 0;