[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>
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@ -218,6 +218,10 @@ extern unsigned long neigh_rand_reach_time(unsigned long base);
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extern void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p,
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struct sk_buff *skb);
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extern struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl, struct net *net, const void *key, struct net_device *dev, int creat);
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extern struct pneigh_entry *__pneigh_lookup(struct neigh_table *tbl,
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struct net *net,
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const void *key,
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struct net_device *dev);
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extern int pneigh_delete(struct neigh_table *tbl, struct net *net, const void *key, struct net_device *dev);
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extern void neigh_app_ns(struct neighbour *n);
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@ -466,6 +466,28 @@ out_neigh_release:
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goto out;
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}
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struct pneigh_entry *__pneigh_lookup(struct neigh_table *tbl,
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struct net *net, const void *pkey, struct net_device *dev)
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{
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struct pneigh_entry *n;
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int key_len = tbl->key_len;
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u32 hash_val = *(u32 *)(pkey + key_len - 4);
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hash_val ^= (hash_val >> 16);
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hash_val ^= hash_val >> 8;
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hash_val ^= hash_val >> 4;
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hash_val &= PNEIGH_HASHMASK;
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for (n = tbl->phash_buckets[hash_val]; n; n = n->next) {
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if (!memcmp(n->key, pkey, key_len) &&
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(n->net == net) &&
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(n->dev == dev || !n->dev))
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break;
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}
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return n;
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}
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struct pneigh_entry * pneigh_lookup(struct neigh_table *tbl,
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struct net *net, const void *pkey,
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struct net_device *dev, int creat)
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@ -2803,6 +2825,7 @@ EXPORT_SYMBOL(neigh_table_init_no_netlink);
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EXPORT_SYMBOL(neigh_update);
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EXPORT_SYMBOL(pneigh_enqueue);
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EXPORT_SYMBOL(pneigh_lookup);
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EXPORT_SYMBOL_GPL(__pneigh_lookup);
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#ifdef CONFIG_ARPD
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EXPORT_SYMBOL(neigh_app_ns);
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@ -676,6 +676,20 @@ static void ndisc_solicit(struct neighbour *neigh, struct sk_buff *skb)
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}
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}
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static struct pneigh_entry *pndisc_check_router(struct net_device *dev,
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struct in6_addr *addr, int *is_router)
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{
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struct pneigh_entry *n;
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read_lock_bh(&nd_tbl.lock);
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n = __pneigh_lookup(&nd_tbl, &init_net, addr, dev);
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if (n != NULL)
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*is_router = (n->flags & NTF_ROUTER);
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read_unlock_bh(&nd_tbl.lock);
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return n;
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}
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static void ndisc_recv_ns(struct sk_buff *skb)
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{
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struct nd_msg *msg = (struct nd_msg *)skb_transport_header(skb);
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@ -692,7 +706,7 @@ static void ndisc_recv_ns(struct sk_buff *skb)
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struct pneigh_entry *pneigh = NULL;
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int dad = ipv6_addr_any(saddr);
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int inc;
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int is_router;
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int is_router = 0;
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if (ipv6_addr_is_multicast(&msg->target)) {
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ND_PRINTK2(KERN_WARNING
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@ -790,8 +804,8 @@ static void ndisc_recv_ns(struct sk_buff *skb)
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if (ipv6_chk_acast_addr(dev, &msg->target) ||
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(idev->cnf.forwarding &&
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(ipv6_devconf.proxy_ndp || idev->cnf.proxy_ndp) &&
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(pneigh = pneigh_lookup(&nd_tbl, &init_net,
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&msg->target, dev, 0)) != NULL)) {
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(pneigh = pndisc_check_router(dev, &msg->target,
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&is_router)) != NULL)) {
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if (!(NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED) &&
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skb->pkt_type != PACKET_HOST &&
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inc != 0 &&
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@ -812,7 +826,7 @@ static void ndisc_recv_ns(struct sk_buff *skb)
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goto out;
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}
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is_router = !!(pneigh ? pneigh->flags & NTF_ROUTER : idev->cnf.forwarding);
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is_router = !!(pneigh ? is_router : idev->cnf.forwarding);
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if (dad) {
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struct in6_addr maddr;
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