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Commit abd1ec4e authored by Jeff Layton's avatar Jeff Layton Committed by J. Bruce Fields
Browse files

lockd: close potential race with rapid lockd_up/lockd_down cycle 



If lockd_down is called very rapidly after lockd_up returns, then
there is a slim chance that lockd() will never be called. kthread()
will return before calling the function, so we'll end up never
actually calling the cleanup functions for the thread.

Signed-off-by: default avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
parent a75c5d01

fs/lockd/svc.c

+13 −20
Original line number Diff line number Diff line
@@ -50,7 +50,7 @@ EXPORT_SYMBOL(nlmsvc_ops); 
static DEFINE_MUTEX(nlmsvc_mutex);

static unsigned int		nlmsvc_users;

static struct task_struct	*nlmsvc_task;

static struct svc_serv		*nlmsvc_serv;

static struct svc_rqst		*nlmsvc_rqst;

int				nlmsvc_grace_period;

unsigned long			nlmsvc_timeout;
@@ -194,20 +194,11 @@ lockd(void *vrqstp) 


		svc_process(rqstp);

	}



	flush_signals(current);

	if (nlmsvc_ops)

		nlmsvc_invalidate_all();

	nlm_shutdown_hosts();



	unlock_kernel();



	nlmsvc_task = NULL;

	nlmsvc_serv = NULL;



	/* Exit the RPC thread */

	svc_exit_thread(rqstp);



	return 0;

}
@@ -254,16 +245,15 @@ int 
lockd_up(int proto) /* Maybe add a 'family' option when IPv6 is supported ?? */

{

	struct svc_serv *serv;

	struct svc_rqst *rqstp;

	int		error = 0;



	mutex_lock(&nlmsvc_mutex);

	/*

	 * Check whether we're already up and running.

	 */

	if (nlmsvc_serv) {

	if (nlmsvc_rqst) {

		if (proto)

			error = make_socks(nlmsvc_serv, proto);

			error = make_socks(nlmsvc_rqst->rq_server, proto);

		goto out;

	}
@@ -288,9 +278,10 @@ lockd_up(int proto) /* Maybe add a 'family' option when IPv6 is supported ?? */ 
	/*

	 * Create the kernel thread and wait for it to start.

	 */

	rqstp = svc_prepare_thread(serv, &serv->sv_pools[0]);

	if (IS_ERR(rqstp)) {

		error = PTR_ERR(rqstp);

	nlmsvc_rqst = svc_prepare_thread(serv, &serv->sv_pools[0]);

	if (IS_ERR(nlmsvc_rqst)) {

		error = PTR_ERR(nlmsvc_rqst);

		nlmsvc_rqst = NULL;

		printk(KERN_WARNING

			"lockd_up: svc_rqst allocation failed, error=%d\n",

			error);
@@ -298,16 +289,15 @@ lockd_up(int proto) /* Maybe add a 'family' option when IPv6 is supported ?? */ 
	}



	svc_sock_update_bufs(serv);

	nlmsvc_serv = rqstp->rq_server;



	nlmsvc_task = kthread_run(lockd, rqstp, serv->sv_name);

	nlmsvc_task = kthread_run(lockd, nlmsvc_rqst, serv->sv_name);

	if (IS_ERR(nlmsvc_task)) {

		error = PTR_ERR(nlmsvc_task);

		svc_exit_thread(nlmsvc_rqst);

		nlmsvc_task = NULL;

		nlmsvc_serv = NULL;

		nlmsvc_rqst = NULL;

		printk(KERN_WARNING

			"lockd_up: kthread_run failed, error=%d\n", error);

		svc_exit_thread(rqstp);

		goto destroy_and_out;

	}
@@ -346,6 +336,9 @@ lockd_down(void) 
		BUG();

	}

	kthread_stop(nlmsvc_task);

	svc_exit_thread(nlmsvc_rqst);

	nlmsvc_task = NULL;

	nlmsvc_rqst = NULL;

out:

	mutex_unlock(&nlmsvc_mutex);

}