usb: cdc_acm: Do not leak URB buffers

When the ACM TTY port is disconnected, the URBs it uses must be killed, and
then the buffers must be freed. Unfortunately a previous refactor removed
the code freeing the buffers because it looked extremely similar to the
code killing the URBs.

As a result, there were many new leaks for each plug/unplug cycle of a
CDC-ACM device, that were detected by kmemleak.

Restore the missing code, and the memory leak is removed.

Fixes: ba8c931d ("cdc-acm: refactor killing urbs")
Signed-off-by: Romain Izard <romain.izard.pro@gmail.com>
Acked-by: Oliver Neukum <oneukum@suse.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/cdc-acm.c

@@ -1514,6 +1514,7 @@ static void acm_disconnect(struct usb_interface *intf)
 {
 	struct acm *acm = usb_get_intfdata(intf);
 	struct tty_struct *tty;
+	int i;
 
 	/* sibling interface is already cleaning up */
 	if (!acm)
@@ -1544,6 +1545,11 @@ static void acm_disconnect(struct usb_interface *intf)
 
 	tty_unregister_device(acm_tty_driver, acm->minor);
 
+	usb_free_urb(acm->ctrlurb);
+	for (i = 0; i < ACM_NW; i++)
+		usb_free_urb(acm->wb[i].urb);
+	for (i = 0; i < acm->rx_buflimit; i++)
+		usb_free_urb(acm->read_urbs[i]);
 	acm_write_buffers_free(acm);
 	usb_free_coherent(acm->dev, acm->ctrlsize, acm->ctrl_buffer, acm->ctrl_dma);
 	acm_read_buffers_free(acm);