From: Johan Hovold <jhovold@gmail.com>
Date: Mon, 26 May 2014 17:23:15 +0000 (+0200)
Subject: USB: usb_wwan: fix write and suspend race
X-Git-Tag: android-x86-4.4-r2~703^2~37^2~116
X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=170fad9e22df0063eba0701adb966786d7a4ec5a;p=android-x86%2Fkernel.git

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: 383cedc3bb43 ("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>
---

diff --git a/drivers/usb/serial/usb_wwan.c b/drivers/usb/serial/usb_wwan.c
index 112693a4100b..2b8f02696c00 100644
--- a/drivers/usb/serial/usb_wwan.c
+++ b/drivers/usb/serial/usb_wwan.c
@@ -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;
 
+	spin_lock_irq(&intfdata->susp_lock);
 	if (PMSG_IS_AUTO(message)) {
-		spin_lock_irq(&intfdata->susp_lock);
-		b = intfdata->in_flight;
-		spin_unlock_irq(&intfdata->susp_lock);
-
-		if (b)
+		if (intfdata->in_flight) {
+			spin_unlock_irq(&intfdata->susp_lock);
 			return -EBUSY;
+		}
 	}
-
-	spin_lock_irq(&intfdata->susp_lock);
 	intfdata->suspended = 1;
 	spin_unlock_irq(&intfdata->susp_lock);
+
 	stop_read_write_urbs(serial);
 
 	return 0;