From: Julian Anastasov <ja@xxxxxx>
commit c2a4ffb70eef39 ("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@xxxxxx>
Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
---
net/netfilter/ipvs/ip_vs_lblc.c | 68 +++++++++++++++++++----------------------
1 file changed, 31 insertions(+), 37 deletions(-)
diff --git a/net/netfilter/ipvs/ip_vs_lblc.c b/net/netfilter/ipvs/ip_vs_lblc.c
index 1383b0e..b39b0e9 100644
--- a/net/netfilter/ipvs/ip_vs_lblc.c
+++ b/net/netfilter/ipvs/ip_vs_lblc.c
@@ -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;
+ if (en) {
+ if (en->dest == dest)
+ return en;
+ ip_vs_lblc_del(en);
+ }
+ en = kmalloc(sizeof(*en), GFP_ATOMIC);
+ if (!en)
+ return NULL;
- ip_vs_dest_hold(dest);
- RCU_INIT_POINTER(en->dest, dest);
+ en->af = dest->af;
+ ip_vs_addr_copy(dest->af, &en->addr, daddr);
+ en->lastuse = jiffies;
- ip_vs_lblc_hash(tbl, en);
- } else {
- struct ip_vs_dest *old_dest;
+ ip_vs_dest_hold(dest);
+ en->dest = 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);
- }
- }
+ 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();
}
--
1.8.4
--
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