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Commit 4ac63ad6 authored by Pavel Emelyanov's avatar Pavel Emelyanov Committed by David S. Miller
Browse files

[IPVS]: Fix sched registration race when checking for name collision. 



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: default avatarPavel Emelyanov <xemul@openvz.org>
Acked-by: default avatarSimon Horman <horms@verge.net.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a014bc8f

net/ipv4/ipvs/ip_vs_sched.c

+14 −13
Original line number Diff line number Diff line
@@ -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) {
@@ -206,6 +193,20 @@ int register_ip_vs_scheduler(struct ip_vs_scheduler *scheduler) 
		return -EINVAL;

	}



	/*

	 *  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

	 */