linux-kernel - Re: [PATCH] usb: musb: Fix potential NULL dereference

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Date:   Fri, 25 Jan 2019 10:37:06 -0600
From:   Bin Liu <b-liu@...com>
To:     "Matwey V. Kornilov" <matwey@....msu.ru>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <matwey.kornilov@...il.com>,
        "open list:MUSB MULTIPOINT HIGH SPEED DUAL-ROLE CONTROLLER" 
        <linux-usb@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: musb: Fix potential NULL dereference

On Wed, Jan 23, 2019 at 08:51:42PM +0300, Matwey V. Kornilov wrote:
> We assign "urb->hcpriv = qh;" a few lines down. The valid qh for the urb is
> hep->hcpriv in this code path.
> 
> Fixes: 714bc5ef3eda ("musb: potential use after free")
> Signed-off-by: Matwey V. Kornilov <matwey@....msu.ru>
> ---
>  drivers/usb/musb/musb_host.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
> index c6118a962d37..6f267716768e 100644
> --- a/drivers/usb/musb/musb_host.c
> +++ b/drivers/usb/musb/musb_host.c
> @@ -2336,7 +2336,7 @@ static int musb_urb_enqueue(
>  		 * odd, rare, error prone, but legal.
>  		 */
>  		kfree(qh);
> -		qh = NULL;
> +		qh = hep->hcpriv;
>  		ret = 0;
>  	} else
>  		ret = musb_schedule(musb, qh,

Did you run into any issue? The original code seems to be correct to me.

Regards,
-Bin.