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

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Message-ID: <20170130112457.GA7075@ulmo.ba.sec>
Date:   Mon, 30 Jan 2017 12:24:57 +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 12:15:53PM +0100, Uwe Kleine-König wrote:
> On Mon, Jan 30, 2017 at 09:54:55AM +0100, Thierry Reding wrote:
> > 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
> 
> Look at platform_match() in drivers/base/platform.c. If
> of_driver_match_device fails it might still match based on
> strcmp(pdev->name, drv->name).

pdev->name is never influenced by the compatible string. The only way
you could create a device that would match this driver is if you were to
manually create it using of_platform_device_create() or similar,
something which we can easily prevent (or revert should anyone ever get
such code into the kernel again).

Thierry

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