* [PATCH][IPVS] Fix sched registration race when checking for name collision
@ 2007-12-03 10:10 Pavel Emelyanov
2007-12-04 1:41 ` Simon Horman
0 siblings, 1 reply; 3+ messages in thread
From: Pavel Emelyanov @ 2007-12-03 10:10 UTC (permalink / raw)
To: Herbert Xu, David Miller
Cc: Linux Netdev List, devel, Wensong Zhang, Simon Horman,
Julian Anastasov
The register_ip_vs_scheduler() checks for the scheduler with the
same name under the read-locked __ip_vs_sched_lock, then drops,
takes it for writing and puts the scheduler in list.
This is racy, since we can have a race window between the lock
being re-locked for writing.
The fix is to search the scheduler with the given name right under
the write-locked __ip_vs_sched_lock.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
---
diff --git a/net/ipv4/ipvs/ip_vs_sched.c b/net/ipv4/ipvs/ip_vs_sched.c
index 1602304..4322358 100644
--- a/net/ipv4/ipvs/ip_vs_sched.c
+++ b/net/ipv4/ipvs/ip_vs_sched.c
@@ -183,19 +183,6 @@ int register_ip_vs_scheduler(struct ip_vs_scheduler *scheduler)
/* increase the module use count */
ip_vs_use_count_inc();
- /*
- * Make sure that the scheduler with this name doesn't exist
- * in the scheduler list.
- */
- sched = ip_vs_sched_getbyname(scheduler->name);
- if (sched) {
- ip_vs_scheduler_put(sched);
- ip_vs_use_count_dec();
- IP_VS_ERR("register_ip_vs_scheduler(): [%s] scheduler "
- "already existed in the system\n", scheduler->name);
- return -EINVAL;
- }
-
write_lock_bh(&__ip_vs_sched_lock);
if (scheduler->n_list.next != &scheduler->n_list) {
@@ -207,6 +194,20 @@ int register_ip_vs_scheduler(struct ip_vs_scheduler *scheduler)
}
/*
+ * Make sure that the scheduler with this name doesn't exist
+ * in the scheduler list.
+ */
+ list_for_each_entry(sched, &ip_vs_schedulers, n_list) {
+ if (strcmp(scheduler->name, sched->name) == 0) {
+ write_unlock_bh(&__ip_vs_sched_lock);
+ ip_vs_use_count_dec();
+ IP_VS_ERR("register_ip_vs_scheduler(): [%s] scheduler "
+ "already existed in the system\n",
+ scheduler->name);
+ return -EINVAL;
+ }
+ }
+ /*
* Add it into the d-linked scheduler list
*/
list_add(&scheduler->n_list, &ip_vs_schedulers);
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH][IPVS] Fix sched registration race when checking for name collision
2007-12-03 10:10 [PATCH][IPVS] Fix sched registration race when checking for name collision Pavel Emelyanov
@ 2007-12-04 1:41 ` Simon Horman
2007-12-04 8:45 ` David Miller
0 siblings, 1 reply; 3+ messages in thread
From: Simon Horman @ 2007-12-04 1:41 UTC (permalink / raw)
To: Pavel Emelyanov
Cc: Herbert Xu, David Miller, Linux Netdev List, devel, Wensong Zhang,
Julian Anastasov
On Mon, Dec 03, 2007 at 01:10:57PM +0300, Pavel Emelyanov wrote:
> The register_ip_vs_scheduler() checks for the scheduler with the
> same name under the read-locked __ip_vs_sched_lock, then drops,
> takes it for writing and puts the scheduler in list.
>
> This is racy, since we can have a race window between the lock
> being re-locked for writing.
>
> The fix is to search the scheduler with the given name right under
> the write-locked __ip_vs_sched_lock.
This looks correct to me.
> Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Simon Horman <horms@verge.net.au>
> ---
>
> diff --git a/net/ipv4/ipvs/ip_vs_sched.c b/net/ipv4/ipvs/ip_vs_sched.c
> index 1602304..4322358 100644
> --- a/net/ipv4/ipvs/ip_vs_sched.c
> +++ b/net/ipv4/ipvs/ip_vs_sched.c
> @@ -183,19 +183,6 @@ int register_ip_vs_scheduler(struct ip_vs_scheduler *scheduler)
> /* increase the module use count */
> ip_vs_use_count_inc();
>
> - /*
> - * Make sure that the scheduler with this name doesn't exist
> - * in the scheduler list.
> - */
> - sched = ip_vs_sched_getbyname(scheduler->name);
> - if (sched) {
> - ip_vs_scheduler_put(sched);
> - ip_vs_use_count_dec();
> - IP_VS_ERR("register_ip_vs_scheduler(): [%s] scheduler "
> - "already existed in the system\n", scheduler->name);
> - return -EINVAL;
> - }
> -
> write_lock_bh(&__ip_vs_sched_lock);
>
> if (scheduler->n_list.next != &scheduler->n_list) {
> @@ -207,6 +194,20 @@ int register_ip_vs_scheduler(struct ip_vs_scheduler *scheduler)
> }
>
> /*
> + * Make sure that the scheduler with this name doesn't exist
> + * in the scheduler list.
> + */
> + list_for_each_entry(sched, &ip_vs_schedulers, n_list) {
> + if (strcmp(scheduler->name, sched->name) == 0) {
> + write_unlock_bh(&__ip_vs_sched_lock);
> + ip_vs_use_count_dec();
> + IP_VS_ERR("register_ip_vs_scheduler(): [%s] scheduler "
> + "already existed in the system\n",
> + scheduler->name);
> + return -EINVAL;
> + }
> + }
> + /*
> * Add it into the d-linked scheduler list
> */
> list_add(&scheduler->n_list, &ip_vs_schedulers);
--
Horms
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH][IPVS] Fix sched registration race when checking for name collision
2007-12-04 1:41 ` Simon Horman
@ 2007-12-04 8:45 ` David Miller
0 siblings, 0 replies; 3+ messages in thread
From: David Miller @ 2007-12-04 8:45 UTC (permalink / raw)
To: horms; +Cc: xemul, herbert, netdev, devel, wensong, ja
From: Simon Horman <horms@verge.net.au>
Date: Tue, 4 Dec 2007 10:41:43 +0900
> On Mon, Dec 03, 2007 at 01:10:57PM +0300, Pavel Emelyanov wrote:
> > The register_ip_vs_scheduler() checks for the scheduler with the
> > same name under the read-locked __ip_vs_sched_lock, then drops,
> > takes it for writing and puts the scheduler in list.
> >
> > This is racy, since we can have a race window between the lock
> > being re-locked for writing.
> >
> > The fix is to search the scheduler with the given name right under
> > the write-locked __ip_vs_sched_lock.
>
> This looks correct to me.
>
> > Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
>
> Acked-by: Simon Horman <horms@verge.net.au>
Also applied, thanks a lot.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2007-12-03 10:10 [PATCH][IPVS] Fix sched registration race when checking for name collision Pavel Emelyanov
2007-12-04 1:41 ` Simon Horman
2007-12-04 8:45 ` David Miller
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