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cdc-acm: fix race between callback and unthrottle

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Abn URB may be may marked free only after the buffer has been
processed or there is a small window during which it could
be submitted on another CPU and overwrite an unprocessed buffer

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Oliver Neukum 2015-03-20 09:24:24 +01:00 committed by Greg Kroah-Hartman
parent c0ab6bb059
commit 36e59e0d70
1 changed files with 10 additions and 2 deletions
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12
drivers/usb/class/cdc-acm.c
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@ -417,25 +417,33 @@ static void acm_read_bulk_callback(struct urb *urb)
struct acm_rb *rb = urb->context;
struct acm *acm = rb->instance;
unsigned long flags;
int status = urb->status;
dev_vdbg(&acm->data->dev, "%s - urb %d, len %d\n", __func__,
rb->index, urb->actual_length);
set_bit(rb->index, &acm->read_urbs_free);
if (!acm->dev) {
set_bit(rb->index, &acm->read_urbs_free);
dev_dbg(&acm->data->dev, "%s - disconnected\n", __func__);
return;
}
if (urb->status) {
set_bit(rb->index, &acm->read_urbs_free);
dev_dbg(&acm->data->dev, "%s - non-zero urb status: %d\n",
__func__, urb->status);
__func__, status);
return;
}
usb_mark_last_busy(acm->dev);
acm_process_read_urb(acm, urb);
/*
* Unthrottle may run on another CPU which needs to see events
* in the same order. Submission has an implict barrier
*/
smp_mb__before_atomic();
set_bit(rb->index, &acm->read_urbs_free);
/* throttle device if requested by tty */
spin_lock_irqsave(&acm->read_lock, flags);