From: Havard Skinnemoen <hskinnemoen@xxxxxxxxxx> There's a race between the USB disconnect handler and the TTY close handler which may cause the acm object to be freed while it's still being used. This may lead to things like http://article.gmane.org/gmane.linux.usb.general/54250 and https://lkml.org/lkml/2011/5/29/64 This is the simplest fix I could come up with. Holding on to open_mutex while closing the TTY device prevents acm_disconnect() from freeing the acm object between acm->port.count drops to 0 and the TTY side of the cleanups are finalized. Signed-off-by: Havard Skinnemoen <hskinnemoen@xxxxxxxxxx> Cc: Oliver Neukum <oliver@xxxxxxxxxxx> Cc: stable <stable@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx> --- drivers/usb/class/cdc-acm.c | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 6960715..e8c564a 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -539,7 +539,6 @@ static void acm_port_down(struct acm *acm) { int i; - mutex_lock(&open_mutex); if (acm->dev) { usb_autopm_get_interface(acm->control); acm_set_control(acm, acm->ctrlout = 0); @@ -551,14 +550,15 @@ static void acm_port_down(struct acm *acm) acm->control->needs_remote_wakeup = 0; usb_autopm_put_interface(acm->control); } - mutex_unlock(&open_mutex); } static void acm_tty_hangup(struct tty_struct *tty) { struct acm *acm = tty->driver_data; tty_port_hangup(&acm->port); + mutex_lock(&open_mutex); acm_port_down(acm); + mutex_unlock(&open_mutex); } static void acm_tty_close(struct tty_struct *tty, struct file *filp) @@ -569,8 +569,9 @@ static void acm_tty_close(struct tty_struct *tty, struct file *filp) shutdown */ if (!acm) return; + + mutex_lock(&open_mutex); if (tty_port_close_start(&acm->port, tty, filp) == 0) { - mutex_lock(&open_mutex); if (!acm->dev) { tty_port_tty_set(&acm->port, NULL); acm_tty_unregister(acm); @@ -582,6 +583,7 @@ static void acm_tty_close(struct tty_struct *tty, struct file *filp) acm_port_down(acm); tty_port_close_end(&acm->port, tty); tty_port_tty_set(&acm->port, NULL); + mutex_unlock(&open_mutex); } static int acm_tty_write(struct tty_struct *tty, -- 1.7.7.3 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
