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USB: fix urb-poison imbalance 

The calls to usb_poison_urb and usb_unpoison_urb are expected to be
balanced. However, if an urb that has not yet been submitted is
poisoned, its reject counter will not be increased as its ep-field is
NULL. A consecutive call to unpoison will thus in fact poison the urb
as its reject counter will be decremented to a negative value,
effectively preventing the urb from being submitted.

Note that there are currently no in-kernel drivers affected by this.

Cc: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2013-03-21 12:36:48 +01:00 committed by Greg Kroah-Hartman
parent 69a3d21257
commit 68a2bed130
1 changed files with 4 additions and 1 deletions
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5
drivers/usb/core/urb.c
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@ -683,10 +683,13 @@ EXPORT_SYMBOL_GPL(usb_kill_urb);
void usb_poison_urb(struct urb *urb)
{
might_sleep();
if (!(urb && urb->dev && urb->ep))
if (!urb)
return;
atomic_inc(&urb->reject);
if (!urb->dev || !urb->ep)
return;
usb_hcd_unlink_urb(urb, -ENOENT);
wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
}