linux-kernel - Re: [PATCH] xen: fix potential shift out-of-bounds in xenhcd_hub

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Date:   Mon, 26 Jun 2023 07:48:05 +0200
From:   Jan Beulich <jbeulich@...e.com>
To:     Zhang Shurong <zhang_shurong@...mail.com>
Cc:     gregkh@...uxfoundation.org, xen-devel@...ts.xenproject.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        jgross@...e.com
Subject: Re: [PATCH] xen: fix potential shift out-of-bounds in
 xenhcd_hub_control()

On 25.06.2023 18:42, Zhang Shurong wrote:
> --- a/drivers/usb/host/xen-hcd.c
> +++ b/drivers/usb/host/xen-hcd.c
> @@ -456,6 +456,8 @@ static int xenhcd_hub_control(struct usb_hcd *hcd, __u16 typeReq, __u16 wValue,
>  			info->ports[wIndex - 1].c_connection = false;
>  			fallthrough;
>  		default:
> +			if (wValue >= 32)
> +				goto error;
>  			info->ports[wIndex - 1].status &= ~(1 << wValue);

Even 31 is out of bounds (as in: UB) as long as it's 1 here rather
than 1u.

Jan