| Message ID | 1537647071-2691-1-git-send-email-t-herzog@gmx.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] cdc-acm: do not reset notification buffer index upon urb unlinking | expand |
On Sa, 2018-09-22 at 22:11 +0200, Tobias Herzog wrote: > 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. Hi, you are right, when you are describing the problem. The fix seems to me to fix a part, albeit a large part of the issue. As far as I can tell, the transfer could be partially succesful, meaning that the driver loses a part in the middle of the notification. Regards Oliver
On Sa, 2018-09-22 at 22:11 +0200, Tobias Herzog wrote: > 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@gmx.de> Acked-by: Oliver Neukum <oneukum@suse.com>
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);
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@gmx.de> --- drivers/usb/class/cdc-acm.c | 1 - 1 file changed, 1 deletion(-)