linux-kernel - [PATCH 1/2] cdc-acm: do not reset notification buffer index upon urb unlinking

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Message-Id: <1537647071-2691-1-git-send-email-t-herzog@gmx.de>
Date:   Sat, 22 Sep 2018 22:11:10 +0200
From:   Tobias Herzog <t-herzog@....de>
To:     oneukum@...e.com
Cc:     gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] cdc-acm: do not reset notification buffer index upon urb unlinking

Resetting the write index of the notification buffer on urb unlink (e.g.
closing a cdc-acm device from userspace) may lead to wrong interpretation
of further received notifications, in case the index is not 0 when urb
unlink happens (i.e. when parts of a notification already have been
transferred). On the device side there is no "reset" of the notification
transimission and thus we would get out of sync with the device.

Signed-off-by: Tobias Herzog <t-herzog@....de>
---
 drivers/usb/class/cdc-acm.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 27346d6..50339ca 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -355,7 +355,6 @@ static void acm_ctrl_irq(struct urb *urb)
 	case -ENOENT:
 	case -ESHUTDOWN:
 		/* this urb is terminated, clean up */
-		acm->nb_index = 0;
 		dev_dbg(&acm->control->dev,
 			"%s - urb shutting down with status: %d\n",
 			__func__, status);
-- 
2.1.4