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

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Date:   Mon, 12 Jun 2017 17:25:44 -0500
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.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

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?

>> +		priv = dev_get_drvdata(&chip->dev);
>>  		tpm_chip_unregister(chip);
>>  		if (priv->have_region)
>>  			atmel_release_region(priv->base, priv->region_size);
>> --
>> 2.5.0
>>

Thank you
--
Gustavo A. R. Silva