[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 <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index d9a02b2..19b8e00 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -466,6 +466,28 @@
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_update);
EXPORT_SYMBOL(pneigh_enqueue);
EXPORT_SYMBOL(pneigh_lookup);
+EXPORT_SYMBOL_GPL(__pneigh_lookup);
#ifdef CONFIG_ARPD
EXPORT_SYMBOL(neigh_app_ns);