[PATCH] USB: cdc-acm: fix double usb_autopm_put_interface() in acm_port_activate()

[PATCH] USB: cdc-acm: fix double usb_autopm_put_interface() in acm_port_activate()

[Alexey Khoroshilov]

If acm_submit_read_urbs() fails in acm_port_activate(), error handling
code calls usb_autopm_put_interface() while it is already called
before acm_submit_read_urbs(). The patch reorganizes error handling code
to avoid double decrement of USB interface's PM-usage counter.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
---
 drivers/usb/class/cdc-acm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 900f7ff805ee..d5d2c922186a 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -518,13 +518,16 @@ static int acm_port_activate(struct tty_port *port, struct tty_struct *tty)
 	if (usb_submit_urb(acm->ctrlurb, GFP_KERNEL)) {
 		dev_err(&acm->control->dev,
 			"%s - usb_submit_urb(ctrl irq) failed\n", __func__);
+		usb_autopm_put_interface(acm->control);
 		goto error_submit_urb;
 	}
 
 	acm->ctrlout = ACM_CTRL_DTR | ACM_CTRL_RTS;
 	if (acm_set_control(acm, acm->ctrlout) < 0 &&
-	    (acm->ctrl_caps & USB_CDC_CAP_LINE))
+	    (acm->ctrl_caps & USB_CDC_CAP_LINE)) {
+		usb_autopm_put_interface(acm->control);
 		goto error_set_control;
+	}
 
 	usb_autopm_put_interface(acm->control);
 
@@ -549,7 +552,6 @@ error_submit_read_urbs:
 error_set_control:
 	usb_kill_urb(acm->ctrlurb);
 error_submit_urb:
-	usb_autopm_put_interface(acm->control);
 error_get_interface:
 disconnected:
 	mutex_unlock(&acm->mutex);
-- 
1.8.3.2

Re: [PATCH] USB: cdc-acm: fix double usb_autopm_put_interface() in acm_port_activate()

[Oliver Neukum]

On Sat, 2014-04-12 at 02:10 +0400, Alexey Khoroshilov wrote:
> If acm_submit_read_urbs() fails in acm_port_activate(), error handling
> code calls usb_autopm_put_interface() while it is already called
> before acm_submit_read_urbs(). The patch reorganizes error handling code
> to avoid double decrement of USB interface's PM-usage counter.
> 
> Found by Linux Driver Verification project (linuxtesting.org).

Nice catch.

> Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Acked-by: Oliver Neukum <oliver@neukum.org>