linux-kernel - Re: [PATCH 1/1] usb: musb: gadget: misplaced out of bounds check

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Message-ID: <20180319162649.GT14921@uda0271908>
Date:   Mon, 19 Mar 2018 11:26:49 -0500
From:   Bin Liu <b-liu@...com>
To:     Heinrich Schuchardt <xypron.glpk@....de>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] usb: musb: gadget: misplaced out of bounds check

Hi,

On Mon, Mar 19, 2018 at 08:12:28AM +0100, Heinrich Schuchardt wrote:
> musb->endpoints[] has array size MUSB_C_NUM_EPS.
> We must check array bounds before accessing the array and not afterwards.
> 
> Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
> ---
>  drivers/usb/musb/musb_gadget_ep0.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/musb/musb_gadget_ep0.c b/drivers/usb/musb/musb_gadget_ep0.c
> index 18da4873e52e..482e7c2f8dc7 100644
> --- a/drivers/usb/musb/musb_gadget_ep0.c
> +++ b/drivers/usb/musb/musb_gadget_ep0.c
> @@ -88,6 +88,11 @@ static int service_tx_status_request(
>  			break;
>  		}
>  
> +		if (epnum >= MUSB_C_NUM_EPS) {

only the LSB 4 bits are the EP number, bit7 is the direction flag. So
you can only compare the LSB 4 bits here.

Regards,
-Bin.