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drivers/net: caif: fix wrong rtnl_is_locked() usage

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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: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Dmitry Tarnyagin <dmitry.tarnyagin@lockless.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Konstantin Khlebnikov 2013-07-08 11:23:04 +04:00 committed by David S. Miller
parent e057590b05
commit 56e0ef527b
1 changed files with 39 additions and 22 deletions
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61
drivers/net/caif/caif_serial.c
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@ -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);
}