From bc4bf5f38cf0a623e6a29f52ec80bfcc56a373c6 Mon Sep 17 00:00:00 2001
From: Pavel Emelyanov <xemul@openvz.org>
Date: Sat, 23 Feb 2008 19:57:02 -0800
Subject: [PATCH] [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>
---
net/core/neighbour.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 4062b88bfc1b6..2328acbd16cdf 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -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)) {
--
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