Re: [PATCH] usb:host: fix divide-by-zero in function fhci_queue_urb

zhuyan (M)
2019-04-16T14:48:48Z

On Tue, 16 Apr 2019 at 11:45:45 +0200, Greg KH wrote:
> On Tue, Apr 09, 2019 at 10:37:12PM +0800, zhuyan wrote:
> > In function fhci_queue_urb, the divisor of expression
> > (urb->transfer_buffer_length % usb_maxpacket(urb->dev, urb->pipe,
> > usb_pipeout(urb->pipe))) may be zero.
>
> How can you hit that?
>
> > When it is zero, unexpected results may occur, so it is necessary to
> > ensure that the divisor is not zero.
> >
> > Signed-off-by: zhuyan <zhuyan34@huawei.com>
>
> I need a "Full" name here, not just a single name. Whatever you use to sign documents is good.
>
> thanks,
>
> greg k-h

In function usb_maxpacket, when ep is NULL, its return value is 0.
Then, in function fhci_queue_urb, the divisor of expression
(urb->transfer_buffer_length % usb_maxpacket(urb->dev, urb->pipe, usb_pipeout(urb->pipe)))
is zero. It will lead to unpredictable results.

Thanks!

Yan Zhu