[3.11.y.z extended stable] Patch "USB: usb_wwan: fix race between write and resume" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    USB: usb_wwan: fix race between write and resume

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 69d4ec981cfbbe408cca6aa751a64c149b854ee6 Mon Sep 17 00:00:00 2001
From: xiao jin <jin.xiao at intel.com>
Date: Mon, 26 May 2014 19:23:14 +0200
Subject: USB: usb_wwan: fix race between write and resume

commit d9e93c08d8d985e5ef89436ebc9f4aad7e31559f upstream.

We find a race between write and resume. usb_wwan_resume run play_delayed()
and spin_unlock, but intfdata->suspended still is not set to zero.
At this time usb_wwan_write is called and anchor the urb to delay
list. Then resume keep running but the delayed urb have no chance
to be commit until next resume. If the time of next resume is far
away, tty will be blocked in tty_wait_until_sent during time. The
race also can lead to writes being reordered.

This patch put play_Delayed and intfdata->suspended together in the
spinlock, it's to avoid the write race during resume.

Fixes: 383cedc3bb43 ("USB: serial: full autosuspend support for the
option driver")

Signed-off-by: xiao jin <jin.xiao at intel.com>
Signed-off-by: Zhang, Qi1 <qi1.zhang at intel.com>
Reviewed-by: David Cohen <david.a.cohen at linux.intel.com>
Signed-off-by: Johan Hovold <jhovold at gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/serial/usb_wwan.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/serial/usb_wwan.c b/drivers/usb/serial/usb_wwan.c
index 7096d0ba1d0f..80c16d84156a 100644
--- a/drivers/usb/serial/usb_wwan.c
+++ b/drivers/usb/serial/usb_wwan.c
@@ -664,17 +664,15 @@ int usb_wwan_resume(struct usb_serial *serial)
 		}
 	}

+	spin_lock_irq(&intfdata->susp_lock);
 	for (i = 0; i < serial->num_ports; i++) {
 		/* walk all ports */
 		port = serial->port[i];
 		portdata = usb_get_serial_port_data(port);

 		/* skip closed ports */
-		spin_lock_irq(&intfdata->susp_lock);
-		if (!portdata || !portdata->opened) {
-			spin_unlock_irq(&intfdata->susp_lock);
+		if (!portdata || !portdata->opened)
 			continue;
-		}

 		for (j = 0; j < N_IN_URB; j++) {
 			urb = portdata->in_urbs[j];
@@ -687,9 +685,7 @@ int usb_wwan_resume(struct usb_serial *serial)
 			}
 		}
 		play_delayed(port);
-		spin_unlock_irq(&intfdata->susp_lock);
 	}
-	spin_lock_irq(&intfdata->susp_lock);
 	intfdata->suspended = 0;
 	spin_unlock_irq(&intfdata->susp_lock);
 err_out:
--
1.9.1