Commit 170fad9e authored May 26, 2014 by Johan Hovold Committed by Greg Kroah-Hartman May 27, 2014

USB: usb_wwan: fix write and suspend race



Fix race between write() and suspend() which could lead to writes being
dropped (or I/O while suspended) if the device is runtime suspended
while a write request is being processed.

Specifically, suspend() releases the susp_lock after determining the
device is idle but before setting the suspended flag, thus leaving a
window where a concurrent write() can submit an urb.

Fixes: 383cedc3 ("USB: serial: full autosuspend support for the
option driver")

Cc: <stable@vger.kernel.org>	# v2.6.32
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent d9e93c08

drivers/usb/serial/usb_wwan.c

+5 −8

Original line number	Diff line number	Diff line
		@@ -579,20 +579,17 @@ static void stop_read_write_urbs(struct usb_serial *serial)
		int usb_wwan_suspend(struct usb_serial *serial, pm_message_t message)
		{
		struct usb_wwan_intf_private *intfdata = serial->private;
		int b;

		if (PMSG_IS_AUTO(message)) {
		spin_lock_irq(&intfdata->susp_lock);
		b = intfdata->in_flight;
		if (PMSG_IS_AUTO(message)) {
		if (intfdata->in_flight) {
		spin_unlock_irq(&intfdata->susp_lock);

		if (b)
		return -EBUSY;
		}

		spin_lock_irq(&intfdata->susp_lock);
		}
		intfdata->suspended = 1;
		spin_unlock_irq(&intfdata->susp_lock);

		stop_read_write_urbs(serial);

		return 0;