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Commit 56e0ef52 authored by Konstantin Khlebnikov's avatar Konstantin Khlebnikov Committed by David S. Miller
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drivers/net: caif: fix wrong rtnl_is_locked() usage 



rtnl_is_locked() doesn't check who holds this lock, it just tells that it's
locked right now. if caif::ldisc_close really can be called under rtrnl_lock
then it should release net device in other context because there is no way
to grab rtnl_lock without deadlock.

This patch adds work which releases these devices. Also this patch fixes calling
dev_close/unregister_netdevice without rtnl_lock from caif_ser_exit().

Signed-off-by: default avatarKonstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Dmitry Tarnyagin <dmitry.tarnyagin@lockless.no>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e057590b

drivers/net/caif/caif_serial.c

+39 −22
Original line number Diff line number Diff line
@@ -35,8 +35,9 @@ MODULE_ALIAS_LDISC(N_CAIF); 
#define OFF 0

#define CAIF_MAX_MTU 4096



/*This list is protected by the rtnl lock. */

static DEFINE_SPINLOCK(ser_lock);

static LIST_HEAD(ser_list);

static LIST_HEAD(ser_release_list);



static bool ser_loop;

module_param(ser_loop, bool, S_IRUGO);
@@ -308,6 +309,28 @@ static void ldisc_tx_wakeup(struct tty_struct *tty) 
}





static void ser_release(struct work_struct *work)

{

	struct list_head list;

	struct ser_device *ser, *tmp;



	spin_lock(&ser_lock);

	list_replace_init(&ser_release_list, &list);

	spin_unlock(&ser_lock);



	if (!list_empty(&list)) {

		rtnl_lock();

		list_for_each_entry_safe(ser, tmp, &list, node) {

			dev_close(ser->dev);

			unregister_netdevice(ser->dev);

			debugfs_deinit(ser);

		}

		rtnl_unlock();

	}

}



static DECLARE_WORK(ser_release_work, ser_release);



static int ldisc_open(struct tty_struct *tty)

{

	struct ser_device *ser;
@@ -321,6 +344,9 @@ static int ldisc_open(struct tty_struct *tty) 
	if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))

		return -EPERM;



	/* release devices to avoid name collision */

	ser_release(NULL);



	sprintf(name, "cf%s", tty->name);

	dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);

	if (!dev)
@@ -341,7 +367,9 @@ static int ldisc_open(struct tty_struct *tty) 
		return -ENODEV;

	}



	spin_lock(&ser_lock);

	list_add(&ser->node, &ser_list);

	spin_unlock(&ser_lock);

	rtnl_unlock();

	netif_stop_queue(dev);

	update_tty_status(ser);
@@ -351,19 +379,13 @@ static int ldisc_open(struct tty_struct *tty) 
static void ldisc_close(struct tty_struct *tty)

{

	struct ser_device *ser = tty->disc_data;

	/* Remove may be called inside or outside of rtnl_lock */

	int islocked = rtnl_is_locked();



	if (!islocked)

		rtnl_lock();

	/* device is freed automagically by net-sysfs */

	dev_close(ser->dev);

	unregister_netdevice(ser->dev);

	list_del(&ser->node);

	debugfs_deinit(ser);

	tty_kref_put(ser->tty);

	if (!islocked)

		rtnl_unlock();



	spin_lock(&ser_lock);

	list_move(&ser->node, &ser_release_list);

	spin_unlock(&ser_lock);

	schedule_work(&ser_release_work);

}



/* The line discipline structure. */
@@ -438,16 +460,11 @@ static int __init caif_ser_init(void) 


static void __exit caif_ser_exit(void)

{

	struct ser_device *ser = NULL;

	struct list_head *node;

	struct list_head *_tmp;



	list_for_each_safe(node, _tmp, &ser_list) {

		ser = list_entry(node, struct ser_device, node);

		dev_close(ser->dev);

		unregister_netdevice(ser->dev);

		list_del(node);

	}

	spin_lock(&ser_lock);

	list_splice(&ser_list, &ser_release_list);

	spin_unlock(&ser_lock);

	ser_release(NULL);

	cancel_work_sync(&ser_release_work);

	tty_unregister_ldisc(N_CAIF);

	debugfs_remove_recursive(debugfsdir);

}