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Commit bc4bf5f3 authored by Pavel Emelyanov's avatar Pavel Emelyanov Committed by David S. Miller
Browse files

[NEIGH]: Fix race between neighbor lookup and table's hash_rnd update. 



The neigh_hash_grow() may update the tbl->hash_rnd value, which 
is used in all tbl->hash callbacks to calculate the hashval.

Two lookup routines may race with this, since they call the 
->hash callback without the tbl->lock held. Since the hash_rnd
is changed with this lock write-locked moving the calls to ->hash
under this lock read-locked closes this gap.

Signed-off-by: default avatarPavel Emelyanov <xemul@openvz.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1840bb13

net/core/neighbour.c

+4 −2
Original line number Diff line number Diff line
@@ -358,11 +358,12 @@ struct neighbour *neigh_lookup(struct neigh_table *tbl, const void *pkey, 
{

	struct neighbour *n;

	int key_len = tbl->key_len;

	u32 hash_val = tbl->hash(pkey, dev);

	u32 hash_val;



	NEIGH_CACHE_STAT_INC(tbl, lookups);



	read_lock_bh(&tbl->lock);

	hash_val = tbl->hash(pkey, dev);

	for (n = tbl->hash_buckets[hash_val & tbl->hash_mask]; n; n = n->next) {

		if (dev == n->dev && !memcmp(n->primary_key, pkey, key_len)) {

			neigh_hold(n);
@@ -379,11 +380,12 @@ struct neighbour *neigh_lookup_nodev(struct neigh_table *tbl, struct net *net, 
{

	struct neighbour *n;

	int key_len = tbl->key_len;

	u32 hash_val = tbl->hash(pkey, NULL);

	u32 hash_val;



	NEIGH_CACHE_STAT_INC(tbl, lookups);



	read_lock_bh(&tbl->lock);

	hash_val = tbl->hash(pkey, NULL);

	for (n = tbl->hash_buckets[hash_val & tbl->hash_mask]; n; n = n->next) {

		if (!memcmp(n->primary_key, pkey, key_len) &&

		    (net == n->dev->nd_net)) {