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[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: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Pavel Emelyanov 2008-02-23 19:57:02 -08:00 committed by David S. Miller
parent 1840bb13c2
commit bc4bf5f38c
1 changed files with 4 additions and 2 deletions
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6
net/core/neighbour.c
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@ -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)) {