Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-12-18 00:53:40 +00:00
Code Issues Packages Projects Releases Wiki Activity

ipvs: do not use dest after ip_vs_dest_put in LBLCR

Browse Source 
commit c5549571f9 ("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@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
This commit is contained in:
Julian Anastasov 2013-09-12 11:21:09 +03:00 committed by Simon Horman
parent 2f3d771a35
commit 742617b176
1 changed files with 20 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
net/netfilter/ipvs/ip_vs_lblcr.c
View File

@ -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 (((__s64)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();
}