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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 <>
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:
/* this urb is terminated, clean up */
- acm->nb_index = 0;
"%s - urb shutting down with status: %d\n",
__func__, status);
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