[PATCH 3.12 112/113] USB: cdc-acm: fix open and suspend race

[Jiri Slaby]

From: Johan Hovold <jhovold@xxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 703df3297fb1950b0aa53e656108eb936d3f21d9 upstream.

We must not do the usb_autopm_put_interface() before submitting the read
urbs or we might end up doing I/O to a suspended device.

Fixes: 088c64f81284 ("USB: cdc-acm: re-write read processing")
Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 drivers/usb/class/cdc-acm.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 545413b76c18..667f16c169d2 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -517,19 +517,15 @@ 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)) {
-		usb_autopm_put_interface(acm->control);
 		goto error_set_control;
 	}
 
-	usb_autopm_put_interface(acm->control);
-
 	/*
 	 * Unthrottle device in case the TTY was closed while throttled.
 	 */
@@ -541,6 +537,8 @@ static int acm_port_activate(struct tty_port *port, struct tty_struct *tty)
 	if (acm_submit_read_urbs(acm, GFP_KERNEL))
 		goto error_submit_read_urbs;
 
+	usb_autopm_put_interface(acm->control);
+
 	mutex_unlock(&acm->mutex);
 
 	return 0;
@@ -553,6 +551,7 @@ 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);
-- 
2.12.0