Re: [PATCH] usb: hub: avoid possible division by zero

Greg Kroah-Hartman
2013-11-23T17:19:40Z

On Sat, Nov 23, 2013 at 05:31:34PM +0100, Johannes Thumshirn wrote:
> Avoid possible division by zero in led_work, if hdev->maxchild is 0.
>
> See also:
> http://buildbot.llvm.linuxfoundation.org/checker/scan-build-latest/report-b65939.html#EndPath
>
> Signed-off-by: Johannes Thumshirn <morbidrsa@gmail.com>
> ---
> drivers/usb/core/hub.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index a7c04e2..8c7aa4e 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -453,7 +453,8 @@ static void led_work (struct work_struct *work)
> unsigned changed = 0;
> int cursor = -1;
>
> - if (hdev->state != USB_STATE_CONFIGURED || hub->quiescing)
> + if (hdev->state != USB_STATE_CONFIGURED || hub->quiescing
> + || hdev->maxchild == 0)

And how can maxchild ever be equal to 0?

Look at where it is assigned (it comes from bNbrPorts in the
descriptor), in hub_configure() and if it is set to 0, the creation of
the structure fails and then this code will never run, right?

So I don't think this is needed, and your checker needs to be fixed.

sorry,

greg k-h