From: Julian Anastasov <ja@xxxxxx>
commit c5549571f975ab ("ipvs: convert lblcr 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 e->dest to be replaced and
defer the ip_vs_dest_put() call by using RCU callback. Now
e->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_lblcr.c | 50 ++++++++++++++++------------------------
1 file changed, 20 insertions(+), 30 deletions(-)
diff --git a/net/netfilter/ipvs/ip_vs_lblcr.c b/net/netfilter/ipvs/ip_vs_lblcr.c
index 3cd85b2..64de585 100644
--- a/net/netfilter/ipvs/ip_vs_lblcr.c
+++ b/net/netfilter/ipvs/ip_vs_lblcr.c
@@ -89,7 +89,7 @@
*/
struct ip_vs_dest_set_elem {
struct list_head list; /* list link */
- struct ip_vs_dest __rcu *dest; /* destination server */
+ struct ip_vs_dest *dest; /* destination server */
struct rcu_head rcu_head;
};
@@ -107,11 +107,7 @@ static void ip_vs_dest_set_insert(struct ip_vs_dest_set *set,
if (check) {
list_for_each_entry(e, &set->list, list) {
- struct ip_vs_dest *d;
-
- d = rcu_dereference_protected(e->dest, 1);
- if (d == dest)
- /* already existed */
+ if (e->dest == dest)
return;
}
}
@@ -121,7 +117,7 @@ static void ip_vs_dest_set_insert(struct ip_vs_dest_set *set,
return;
ip_vs_dest_hold(dest);
- RCU_INIT_POINTER(e->dest, dest);
+ e->dest = dest;
list_add_rcu(&e->list, &set->list);
atomic_inc(&set->size);
@@ -129,22 +125,27 @@ static void ip_vs_dest_set_insert(struct ip_vs_dest_set *set,
set->lastmod = jiffies;
}
+static void ip_vs_lblcr_elem_rcu_free(struct rcu_head *head)
+{
+ struct ip_vs_dest_set_elem *e;
+
+ e = container_of(head, struct ip_vs_dest_set_elem, rcu_head);
+ ip_vs_dest_put(e->dest);
+ kfree(e);
+}
+
static void
ip_vs_dest_set_erase(struct ip_vs_dest_set *set, struct ip_vs_dest *dest)
{
struct ip_vs_dest_set_elem *e;
list_for_each_entry(e, &set->list, list) {
- struct ip_vs_dest *d;
-
- d = rcu_dereference_protected(e->dest, 1);
- if (d == dest) {
+ if (e->dest == dest) {
/* HIT */
atomic_dec(&set->size);
set->lastmod = jiffies;
- ip_vs_dest_put(dest);
list_del_rcu(&e->list);
- kfree_rcu(e, rcu_head);
+ call_rcu(&e->rcu_head, ip_vs_lblcr_elem_rcu_free);
break;
}
}
@@ -155,16 +156,8 @@ static void ip_vs_dest_set_eraseall(struct ip_vs_dest_set *set)
struct ip_vs_dest_set_elem *e, *ep;
list_for_each_entry_safe(e, ep, &set->list, list) {
- struct ip_vs_dest *d;
-
- d = rcu_dereference_protected(e->dest, 1);
- /*
- * We don't kfree dest because it is referred either
- * by its service or by the trash dest list.
- */
- ip_vs_dest_put(d);
list_del_rcu(&e->list);
- kfree_rcu(e, rcu_head);
+ call_rcu(&e->rcu_head, ip_vs_lblcr_elem_rcu_free);
}
}
@@ -175,12 +168,9 @@ static inline struct ip_vs_dest *ip_vs_dest_set_min(struct ip_vs_dest_set *set)
struct ip_vs_dest *dest, *least;
int loh, doh;
- if (set == NULL)
- return NULL;
-
/* select the first destination server, whose weight > 0 */
list_for_each_entry_rcu(e, &set->list, list) {
- least = rcu_dereference(e->dest);
+ least = e->dest;
if (least->flags & IP_VS_DEST_F_OVERLOAD)
continue;
@@ -195,7 +185,7 @@ static inline struct ip_vs_dest *ip_vs_dest_set_min(struct ip_vs_dest_set *set)
/* find the destination with the weighted least load */
nextstage:
list_for_each_entry_continue_rcu(e, &set->list, list) {
- dest = rcu_dereference(e->dest);
+ dest = e->dest;
if (dest->flags & IP_VS_DEST_F_OVERLOAD)
continue;
@@ -232,7 +222,7 @@ static inline struct ip_vs_dest *ip_vs_dest_set_max(struct ip_vs_dest_set *set)
/* select the first destination server, whose weight > 0 */
list_for_each_entry(e, &set->list, list) {
- most = rcu_dereference_protected(e->dest, 1);
+ most = e->dest;
if (atomic_read(&most->weight) > 0) {
moh = ip_vs_dest_conn_overhead(most);
goto nextstage;
@@ -243,7 +233,7 @@ static inline struct ip_vs_dest *ip_vs_dest_set_max(struct ip_vs_dest_set *set)
/* find the destination with the weighted most load */
nextstage:
list_for_each_entry_continue(e, &set->list, list) {
- dest = rcu_dereference_protected(e->dest, 1);
+ dest = e->dest;
doh = ip_vs_dest_conn_overhead(dest);
/* moh/mw < doh/dw ==> moh*dw < doh*mw, where mw,dw>0 */
if ((moh * atomic_read(&dest->weight) <
@@ -819,7 +809,7 @@ static void __exit ip_vs_lblcr_cleanup(void)
{
unregister_ip_vs_scheduler(&ip_vs_lblcr_scheduler);
unregister_pernet_subsys(&ip_vs_lblcr_ops);
- synchronize_rcu();
+ rcu_barrier();
}
--
1.8.4
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