linux-kernel - [PATCH 4.4 068/117] usb: cdc-acm: handle unlinked urb in acm read callback

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Date:	Sun, 14 Feb 2016 14:21:45 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Tang Jian Qiang <jianqiang.tang@...el.com>,
	Lu Baolu <baolu.lu@...ux.intel.com>,
	Oliver Neukum <oneukum@...e.com>
Subject: [PATCH 4.4 068/117] usb: cdc-acm: handle unlinked urb in acm read callback

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lu Baolu <baolu.lu@...ux.intel.com>

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@...el.com>
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Acked-by: Oliver Neukum <oneukum@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/class/cdc-acm.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -428,7 +428,8 @@ static void acm_read_bulk_callback(struc
 		set_bit(rb->index, &acm->read_urbs_free);
 		dev_dbg(&acm->data->dev, "%s - non-zero urb status: %d\n",
 							__func__, status);
-		return;
+		if ((status != -ENOENT) || (urb->actual_length == 0))
+			return;
 	}
 
 	usb_mark_last_busy(acm->dev);