linux-kernel - Re: [PATCH] char: tmp: fix potential null pointer dereference

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Date:   Tue, 13 Jun 2017 21:03:19 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Cc:     Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] char: tmp: fix potential null pointer dereference

On Mon, Jun 12, 2017 at 05:25:44PM -0500, Gustavo A. R. Silva wrote:
> Hi Jarkko,
> 
> Please, see my comments below
> 
> Quoting Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>:
> 
> > On Tue, May 30, 2017 at 04:51:23PM -0500, Gustavo A. R. Silva wrote:
> > > NULL check at line 147: if (chip) {, implies chip might be NULL.
> > > Function dev_get_drvdata() dereference pointer chip.
> > > Move pointer priv assignment inside the IF block that checks
> > > pointer chip.
> > > 
> > > Addresses-Coverity-ID: 1397646
> > > Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
> > 
> > It cannot be.
> > 
> 
> I got it.
> 
> > /Jarkko
> > 
> > > ---
> > >  drivers/char/tpm/tpm_atmel.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/char/tpm/tpm_atmel.c b/drivers/char/tpm/tpm_atmel.c
> > > index 0d322ab..0826efd 100644
> > > --- a/drivers/char/tpm/tpm_atmel.c
> > > +++ b/drivers/char/tpm/tpm_atmel.c
> > > @@ -142,9 +142,10 @@ static struct platform_device *pdev;
> > >  static void atml_plat_remove(void)
> > >  {
> > >  	struct tpm_chip *chip = dev_get_drvdata(&pdev->dev);
> > > -	struct tpm_atmel_priv *priv = dev_get_drvdata(&chip->dev);
> > > +	struct tpm_atmel_priv *priv;
> > > 
> > >  	if (chip) {
> 
> So, this NULL check could be removed?

Yes, this would be right way to fix it.

/Jarkko