Re: [PATCH] usb: host: max3421: Fix shift-out-of-bounds in max3421_hub_control()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Sat, May 16, 2026 at 08:01:46PM -0400, pip-izony wrote:
> From: Seungjin Bae <eeodqql09@gmail.com>
> 
> So if a malicious userspace task with access to the root hub via
> /dev/bus/usb/.../001 issues a USBDEVFS_CONTROL ioctl with `wValue`
> greater than or equal to 32, the left shift operation invokes
> shift-out-of-bounds undefined behavior. This results in arbitrary
> bit corruption of `port_status`, including the normally-immutable
> change bits, which can bypass internal state checks and confuse the
> hub status.
> 
> Fix this by rejecting requests whose `value` exceeds the shift width
> before performing the shift.
> 
> Fixes: 2d53139f3162 ("Add support for using a MAX3421E chip as a host driver.")
> Signed-off-by: Seungjin Bae <eeodqql09@gmail.com>
> ---
>  drivers/usb/host/max3421-hcd.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/usb/host/max3421-hcd.c b/drivers/usb/host/max3421-hcd.c
> index 0e17c988d36a..3d6b351dcb1a 100644
> --- a/drivers/usb/host/max3421-hcd.c
> +++ b/drivers/usb/host/max3421-hcd.c
> @@ -1694,6 +1694,8 @@ max3421_hub_control(struct usb_hcd *hcd, u16 type_req, u16 value, u16 index,
>  						!pdata->vbus_active_level);
>  			fallthrough;
>  		default:
> +			if (value >= 32)
> +				goto error;

Cool, what tool found this?  I've been running some static checkers and
I don't think it turned this one up yet.

thanks,

greg k-h