[3.11.y.z extended stable] Patch "USB: cdc-acm: fix potential urb leak and PM imbalance in write" 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: cdc-acm: fix potential urb leak and PM imbalance in write

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 329f59ce357fd4cd9ae923c6c53a6eb9b7e425a7 Mon Sep 17 00:00:00 2001
From: Johan Hovold <jhovold at gmail.com>
Date: Mon, 26 May 2014 19:23:41 +0200
Subject: USB: cdc-acm: fix potential urb leak and PM imbalance in write

commit 183a45087d126d126e8dd1d9b2602fc129dff9ad upstream.

Make sure to check return value of autopm get in write() in order to
avoid urb leak and PM counter imbalance on errors.

Fixes: 11ea859d64b6 ("USB: additional power savings for cdc-acm devices
that support remote wakeup")

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/class/cdc-acm.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 014a1aa3f950..dc5cfa5a1118 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -654,7 +654,13 @@ static int acm_tty_write(struct tty_struct *tty,
 	memcpy(wb->buf, buf, count);
 	wb->len = count;

-	usb_autopm_get_interface_async(acm->control);
+	stat = usb_autopm_get_interface_async(acm->control);
+	if (stat) {
+		wb->use = 0;
+		spin_unlock_irqrestore(&acm->write_lock, flags);
+		return stat;
+	}
+
 	if (acm->susp_count) {
 		usb_anchor_urb(wb->urb, &acm->delayed);
 		spin_unlock_irqrestore(&acm->write_lock, flags);
--
1.9.1