linux-kernel - Re: usb/media/cx231xx: null-ptr-deref in cx231xx_usb

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Message-ID: <20170921083739.GI3198@localhost>
Date:   Thu, 21 Sep 2017 10:37:39 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Oleh Kravchenko <oleg@....org.ua>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Johan Hovold <johan@...nel.org>, 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>
Subject: Re: usb/media/cx231xx: null-ptr-deref in cx231xx_usb_probe

On Wed, Sep 20, 2017 at 08:54:08PM +0200, Andrey Konovalov wrote:
> Hi!
> 
> I've got the following report while fuzzing the kernel with syzkaller.
> 
> On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18).
> 
> The null-ptr-deref happens on assoc_desc->bFirstInterface, where
> assoc_desc = udev->actconfig->intf_assoc[0]. There seems to be no
> check that the device actually contains an Interface Association
> Descriptor.

That is indeed a bug; I'll respond to this mail with a fix.

Thanks,
Johan