ipv6: Use universal hash for NDISC.

In order to perform a proper universal hash on a vector of integers,
we have to use different universal hashes on each vector element.

Which means we need 4 different hash randoms for ipv6.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 3 deletions

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 4af151e1bf5d..e287346e0934 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -322,11 +322,18 @@ out_entries:
         goto out;
 }
 
+static void neigh_get_hash_rnd(u32 *x)
+{
+        get_random_bytes(x, sizeof(*x));
+        *x |= 1;
+}
+
 static struct neigh_hash_table *neigh_hash_alloc(unsigned int shift)
 {
         size_t size = (1 << shift) * sizeof(struct neighbour *);
         struct neigh_hash_table *ret;
         struct neighbour __rcu **buckets;
+        int i;
 
         ret = kmalloc(sizeof(*ret), GFP_ATOMIC);
         if (!ret)
@@ -343,8 +350,8 @@ static struct neigh_hash_table *neigh_hash_alloc(unsigned int shift)
         }
         ret->hash_buckets = buckets;
         ret->hash_shift = shift;
-        get_random_bytes(&ret->hash_rnd, sizeof(ret->hash_rnd));
-        ret->hash_rnd |= 1;
+        for (i = 0; i < NEIGH_NUM_HASH_RND; i++)
+                neigh_get_hash_rnd(&ret->hash_rnd[i]);
         return ret;
 }
 
@@ -1828,7 +1835,7 @@ static int neightbl_fill_info(struct sk_buff *skb, struct neigh_table *tbl,
 
                 rcu_read_lock_bh();
                 nht = rcu_dereference_bh(tbl->nht);
-                ndc.ndtc_hash_rnd = nht->hash_rnd;
+                ndc.ndtc_hash_rnd = nht->hash_rnd[0];
                 ndc.ndtc_hash_mask = ((1 << nht->hash_shift) - 1);
                 rcu_read_unlock_bh();