linux-kernel - Re: [PATCH] I2c: busses - Fix possible NULL derefrence.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 30 Jan 2017 09:54:55 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:     Shailendra Verma <shailendra.v@...sung.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Stephen Warren <swarren@...dotorg.org>,
        Alexandre Courbot <gnurou@...il.com>,
        linux-i2c@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, p.shailesh@...sung.com,
        ashish.kalra@...sung.com,
        Shailendra Verma <shailendra.capricorn@...il.com>
Subject: Re: [PATCH] I2c: busses - Fix possible NULL derefrence.

On Mon, Jan 30, 2017 at 09:07:15AM +0100, Uwe Kleine-König wrote:
> Hello,
> 
> On Mon, Jan 30, 2017 at 08:12:17AM +0100, Thierry Reding wrote:
> > On Mon, Jan 30, 2017 at 10:33:07AM +0530, Shailendra Verma wrote:
> > > of_device_get_match_data could return NULL, and so can cause
> > > a NULL pointer dereference later.
> > > 
> > > Signed-off-by: Shailendra Verma <shailendra.v@...sung.com>
> > > ---
> > >  drivers/i2c/busses/i2c-tegra.c |    4 ++++
> > >  1 file changed, 4 insertions(+)
> > 
> > This will never happen. Any match in the OF table that would cause the
> > ->probe() to occur has a valid .data pointer associated with it.
> 
> Theoretically you could (I think) bind that driver to a node with
> 
> 	compatible = "tegra-i2c";

That's not a valid compatible string and I don't think this could end up
anywhere that would make the driver bind. Even if it did I think it'd be
good to crash rather than error out to make it very obvious that you've
made a mistake that needs to be immediately fixed.

If you error out it's much more likely that people won't notice.

> Anyhow, even if today there was no possibility this could happen, that's
> something that might easily be changed by a future change. So I doubt
> "this will never happen" stays true for sure and being defensive is a
> good idea.

Let's revisit this again *if* this ever becomes a real issue. There's no
use in adding dead code to the kernel to handle hypothetical use-cases.

> And even a BUG would be better than a silent NULL pointer dereference.

I've never encountered a NULL pointer dereference that was silent. =)

Thierry

Download attachment "signature.asc" of type "application/pgp-signature" (834 bytes)