[3.13.y-ckt stable] Patch "usb: cdc-acm: handle unlinked urb in acm read callback" has been added to the 3.13.y-ckt tree

[Kamal Mostafa]

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

    usb: cdc-acm: handle unlinked urb in acm read callback

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt35.

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

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 72755351fd169abf496dafcca0d4cfcf8871ad56 Mon Sep 17 00:00:00 2001
From: Lu Baolu <baolu.lu at linux.intel.com>
Date: Wed, 30 Dec 2015 12:59:08 +0800
Subject: usb: cdc-acm: handle unlinked urb in acm read callback

commit 19454462acb1bdef80542061bdc9b410e4ed1ff6 upstream.

In current acm driver, the bulk-in callback function ignores the
URBs unlinked in usb core.

This causes unexpected data loss in some cases. For example,
runtime suspend entry will unlinked all urbs and set urb->status
to -ENOENT even those urbs might have data not processed yet.
Hence, data loss occurs.

This patch lets bulk-in callback function handle unlinked urbs
to avoid data loss.

Signed-off-by: Tang Jian Qiang <jianqiang.tang at intel.com>
Signed-off-by: Lu Baolu <baolu.lu at linux.intel.com>
Acked-by: Oliver Neukum <oneukum at suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
[ kamal: backport to 3.19-stable: context ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/usb/class/cdc-acm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 87f216d..917cfdc 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -399,7 +399,8 @@ static void acm_read_bulk_callback(struct urb *urb)
 	if (urb->status) {
 		dev_dbg(&acm->data->dev, "%s - non-zero urb status: %d\n",
 							__func__, urb->status);
-		return;
+		if ((urb->status != -ENOENT) || (urb->actual_length == 0))
+			return;
 	}
 	acm_process_read_urb(acm, urb);

--
1.9.1