Messages in this thread Patch in this message |  | | | Date | Tue, 22 Nov 2011 16:23:42 -0800 | | From | Greg KH <> | | Subject | [35/53] USB: cdc-acm: Fix disconnect() vs close() race |
| |
3.0-stable review patch. If anyone has any objections, please let me know.
------------------ From: Havard Skinnemoen <hskinnemoen@google.com>
commit 5dc2470c602da8851907ec18942cd876c3b4ecc1 upstream.
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@google.com> Cc: Oliver Neukum <oliver@neukum.name> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/usb/class/cdc-acm.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- 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 *ac { 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 *ac 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_str 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_str 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,
|  |