From fa86d322d89995fef1bfb5cc768b89d8c22ea0d9 Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Mon, 24 Mar 2008 14:48:59 -0700 Subject: [NEIGH]: Fix race between pneigh deletion and ipv6's ndisc_recv_ns (v3). Proxy neighbors do not have any reference counting, so any caller of pneigh_lookup (unless it's a netlink triggered add/del routine) should _not_ perform any actions on the found proxy entry. There's one exception from this rule - the ipv6's ndisc_recv_ns() uses found entry to check the flags for NTF_ROUTER. This creates a race between the ndisc and pneigh_delete - after the pneigh is returned to the caller, the nd_tbl.lock is dropped and the deleting procedure may proceed. One of the fixes would be to add a reference counting, but this problem exists for ndisc only. Besides such a patch would be too big for -rc4. So I propose to introduce a __pneigh_lookup() which is supposed to be called with the lock held and use it in ndisc code to check the flags on alive pneigh entry. Changes from v2: As David noticed, Exported the __pneigh_lookup() to ipv6 module. The checkpatch generates a warning on it, since the EXPORT_SYMBOL does not follow the symbol itself, but in this file all the exports come at the end, so I decided no to break this harmony. Changes from v1: Fixed comments from YOSHIFUJI - indentation of prototype in header and the pndisc_check_router() name - and a compilation fix, pointed by Daniel - the is_routed was (falsely) considered as uninitialized by gcc. Signed-off-by: Pavel Emelyanov Signed-off-by: David S. Miller --- net/core/neighbour.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'net/core/neighbour.c') diff --git a/net/core/neighbour.c b/net/core/neighbour.c index d9a02b2cc289..19b8e003f150 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -466,6 +466,28 @@ out_neigh_release: goto out; } +struct pneigh_entry *__pneigh_lookup(struct neigh_table *tbl, + struct net *net, const void *pkey, struct net_device *dev) +{ + struct pneigh_entry *n; + int key_len = tbl->key_len; + u32 hash_val = *(u32 *)(pkey + key_len - 4); + + hash_val ^= (hash_val >> 16); + hash_val ^= hash_val >> 8; + hash_val ^= hash_val >> 4; + hash_val &= PNEIGH_HASHMASK; + + for (n = tbl->phash_buckets[hash_val]; n; n = n->next) { + if (!memcmp(n->key, pkey, key_len) && + (n->net == net) && + (n->dev == dev || !n->dev)) + break; + } + + return n; +} + struct pneigh_entry * pneigh_lookup(struct neigh_table *tbl, struct net *net, const void *pkey, struct net_device *dev, int creat) @@ -2803,6 +2825,7 @@ EXPORT_SYMBOL(neigh_table_init_no_netlink); EXPORT_SYMBOL(neigh_update); EXPORT_SYMBOL(pneigh_enqueue); EXPORT_SYMBOL(pneigh_lookup); +EXPORT_SYMBOL_GPL(__pneigh_lookup); #ifdef CONFIG_ARPD EXPORT_SYMBOL(neigh_app_ns); -- cgit v1.2.3