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 <[EMAIL PROTECTED]>
Acked-by: Simon Horman <[EMAIL PROTECTED]>
> ---
>
> 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
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