On Tue, 26 Feb 2013, Johan Hovold wrote:
> 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.
>
> Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
> ---
> drivers/usb/core/urb.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
> index e0d9d94..16927fa 100644
> --- a/drivers/usb/core/urb.c
> +++ b/drivers/usb/core/urb.c
> @@ -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);
> }
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
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