Re: [PATCH] usb: xhci: fix potential divide-by-zero in xhci_urb_enqueue()

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

On Sat, Jan 10, 2026 at 01:34:21PM -0500, pip-izony wrote:
> From: Seungjin Bae <eeodqql09@gmail.com>
> 
> The `xhci_urb_enqueue()` validates Bulk OUT transfers by checking if the
> buffer length is a multiple of the packet size. However, it doesn't check
> whether the endpoint's `wMaxPacketSize` is zero before using it as a
> divisor in a modulo operation.
> 
> If a malicious USB device sends a descriptor with `wMaxPacketSize` set to
> 0, it triggers a divide-by-zero exception (kernel panic). This allows an
> attacker with physical access to crash the system, leading to a Denial of
> Service.

Shouldn't such a device have been rejected before it got here?  When can
this happen, after a driver is bound to a device or before it?

thanks,

greg k-h