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ipvs: do not use dest after ip_vs_dest_put in LBLC

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commit c2a4ffb70e ("ipvs: convert lblc scheduler to rcu")
allows RCU readers to use dest after calling ip_vs_dest_put().
In the corner case it can race with ip_vs_dest_trash_expire()
which can release the dest while it is being returned to the
RCU readers as scheduling result.

To fix the problem do not allow en->dest to be replaced and
defer the ip_vs_dest_put() call by using RCU callback. Now
en->dest does not need to be RCU pointer.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
This commit is contained in:
Julian Anastasov 2013-09-12 11:21:08 +03:00 committed by Simon Horman
parent bcbde4c0a7
commit 2f3d771a35
1 changed files with 33 additions and 39 deletions
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72
net/netfilter/ipvs/ip_vs_lblc.c
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@ -93,7 +93,7 @@ struct ip_vs_lblc_entry {
struct hlist_node list;
int af; /* address family */
union nf_inet_addr addr; /* destination IP address */
struct ip_vs_dest __rcu *dest; /* real server (cache) */
struct ip_vs_dest *dest; /* real server (cache) */
unsigned long lastuse; /* last used time */
struct rcu_head rcu_head;
};
@ -130,20 +130,21 @@ static struct ctl_table vs_vars_table[] = {
};
#endif
static inline void ip_vs_lblc_free(struct ip_vs_lblc_entry *en)
static void ip_vs_lblc_rcu_free(struct rcu_head *head)
{
struct ip_vs_dest *dest;
struct ip_vs_lblc_entry *en = container_of(head,
struct ip_vs_lblc_entry,
rcu_head);
hlist_del_rcu(&en->list);
/*
* We don't kfree dest because it is referred either by its service
* or the trash dest list.
*/
dest = rcu_dereference_protected(en->dest, 1);
ip_vs_dest_put(dest);
kfree_rcu(en, rcu_head);
ip_vs_dest_put(en->dest);
kfree(en);
}
static inline void ip_vs_lblc_del(struct ip_vs_lblc_entry *en)
{
hlist_del_rcu(&en->list);
call_rcu(&en->rcu_head, ip_vs_lblc_rcu_free);
}
/*
* Returns hash value for IPVS LBLC entry
@ -203,30 +204,23 @@ ip_vs_lblc_new(struct ip_vs_lblc_table *tbl, const union nf_inet_addr *daddr,
struct ip_vs_lblc_entry *en;
en = ip_vs_lblc_get(dest->af, tbl, daddr);
if (!en) {
en = kmalloc(sizeof(*en), GFP_ATOMIC);
if (!en)
return NULL;
en->af = dest->af;
ip_vs_addr_copy(dest->af, &en->addr, daddr);
en->lastuse = jiffies;
ip_vs_dest_hold(dest);
RCU_INIT_POINTER(en->dest, dest);
ip_vs_lblc_hash(tbl, en);
} else {
struct ip_vs_dest *old_dest;
old_dest = rcu_dereference_protected(en->dest, 1);
if (old_dest != dest) {
ip_vs_dest_put(old_dest);
ip_vs_dest_hold(dest);
/* No ordering constraints for refcnt */
RCU_INIT_POINTER(en->dest, dest);
}
if (en) {
if (en->dest == dest)
return en;
ip_vs_lblc_del(en);
}
en = kmalloc(sizeof(*en), GFP_ATOMIC);
if (!en)
return NULL;
en->af = dest->af;
ip_vs_addr_copy(dest->af, &en->addr, daddr);
en->lastuse = jiffies;
ip_vs_dest_hold(dest);
en->dest = dest;
ip_vs_lblc_hash(tbl, en);
return en;
}
@ -246,7 +240,7 @@ static void ip_vs_lblc_flush(struct ip_vs_service *svc)
tbl->dead = 1;
for (i=0; i<IP_VS_LBLC_TAB_SIZE; i++) {
hlist_for_each_entry_safe(en, next, &tbl->bucket[i], list) {
ip_vs_lblc_free(en);
ip_vs_lblc_del(en);
atomic_dec(&tbl->entries);
}
}
@ -281,7 +275,7 @@ static inline void ip_vs_lblc_full_check(struct ip_vs_service *svc)
sysctl_lblc_expiration(svc)))
continue;
ip_vs_lblc_free(en);
ip_vs_lblc_del(en);
atomic_dec(&tbl->entries);
}
spin_unlock(&svc->sched_lock);
@ -335,7 +329,7 @@ static void ip_vs_lblc_check_expire(unsigned long data)
if (time_before(now, en->lastuse + ENTRY_TIMEOUT))
continue;
ip_vs_lblc_free(en);
ip_vs_lblc_del(en);
atomic_dec(&tbl->entries);
goal--;
}
@ -511,7 +505,7 @@ ip_vs_lblc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
* free up entries from the trash at any time.
*/
dest = rcu_dereference(en->dest);
dest = en->dest;
if ((dest->flags & IP_VS_DEST_F_AVAILABLE) &&
atomic_read(&dest->weight) > 0 && !is_overloaded(dest, svc))
goto out;
@ -631,7 +625,7 @@ static void __exit ip_vs_lblc_cleanup(void)
{
unregister_ip_vs_scheduler(&ip_vs_lblc_scheduler);
unregister_pernet_subsys(&ip_vs_lblc_ops);
synchronize_rcu();
rcu_barrier();
}