linux-kernel - Re: [PATCH] [media] cx231xx-cards: fix NULL-deref on missing association descriptor

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Date:   Thu, 21 Sep 2017 16:00:20 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Oleh Kravchenko <oleg@....org.ua>, linux-media@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>,
        stable <stable@...r.kernel.org>,
        Sri Deevi <Srinivasa.Deevi@...exant.com>
Subject: Re: [PATCH] [media] cx231xx-cards: fix NULL-deref on missing
 association descriptor

On Thu, Sep 21, 2017 at 10:40 AM, Johan Hovold <johan@...nel.org> wrote:
> Make sure to check that we actually have an Interface Association
> Descriptor before dereferencing it during probe to avoid dereferencing a
> NULL-pointer.
>
> Fixes: e0d3bafd0258 ("V4L/DVB (10954): Add cx231xx USB driver")
> Cc: stable <stable@...r.kernel.org>     # 2.6.30
> Cc: Sri Deevi <Srinivasa.Deevi@...exant.com>
> Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
> Signed-off-by: Johan Hovold <johan@...nel.org>

Tested-by: Andrey Konovalov <andreyknvl@...gle.com>

Thanks!

> ---
>  drivers/media/usb/cx231xx/cx231xx-cards.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/media/usb/cx231xx/cx231xx-cards.c b/drivers/media/usb/cx231xx/cx231xx-cards.c
> index e0daa9b6c2a0..9b742d569fb5 100644
> --- a/drivers/media/usb/cx231xx/cx231xx-cards.c
> +++ b/drivers/media/usb/cx231xx/cx231xx-cards.c
> @@ -1684,7 +1684,7 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
>         nr = dev->devno;
>
>         assoc_desc = udev->actconfig->intf_assoc[0];
> -       if (assoc_desc->bFirstInterface != ifnum) {
> +       if (!assoc_desc || assoc_desc->bFirstInterface != ifnum) {
>                 dev_err(d, "Not found matching IAD interface\n");
>                 retval = -ENODEV;
>                 goto err_if;
> --
> 2.14.1
>