linux-kernel - [PATCH 1/1] usb: cdc-acm: handle unlinked urb in acm read callback

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Date:	Tue, 29 Dec 2015 13:46:42 +0800
From:	Lu Baolu <baolu.lu@...ux.intel.com>
To:	Oliver Neukum <oliver@...kum.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Lu Baolu <baolu.lu@...ux.intel.com>,
	Tang Jian Qiang <jianqiang.tang@...el.com>,
	stable@...r.kernel.org
Subject: [PATCH 1/1] usb: cdc-acm: handle unlinked urb in acm read callback

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>
Cc: stable@...r.kernel.org
---
 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 26ca4f9..8cd193b 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -428,7 +428,8 @@ static void acm_read_bulk_callback(struct urb *urb)
 		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);
-- 
2.1.4

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