linux-kernel - Re: [PATCH] TPM: integrity fix

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Message-ID: <498B0E5A.1020709@linux.vnet.ibm.com>
Date:	Thu, 05 Feb 2009 14:05:46 -0200
From:	Rajiv Andrade <srajiv@...ux.vnet.ibm.com>
To:	"Serge E. Hallyn" <serue@...ibm.com>
CC:	linux-kernel@...r.kernel.org, jmorris@...ei.org,
	akpm@...ux-foundation.org, safford@...son.ibm.com,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Subject: Re: [PATCH] TPM: integrity fix

Serge E. Hallyn wrote:
> Quoting Rajiv Andrade (srajiv@...ux.vnet.ibm.com):
>   
>> Fix to function which is called by IMA, now tpm_chip_find_get() considers the case in which the machine doesn't have a TPM or, if it has, its TPM isn't enabled.
>>
>> Signed-off-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
>> Signed-off-by: Rajiv Andrade <srajiv@...ux.vnet.ibm.com>
>>     
>
> Is this to fix James' problem with IMA on bootup?
>
>   
Yes.
> Acked-by: Serge Hallyn <serue@...ibm.com>
>
>   
>> ---
>>  drivers/char/tpm/tpm.c |    8 +++++---
>>  1 files changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
>> index 0387965..912a473 100644
>> --- a/drivers/char/tpm/tpm.c
>> +++ b/drivers/char/tpm/tpm.c
>> @@ -666,18 +666,20 @@ EXPORT_SYMBOL_GPL(tpm_show_temp_deactivated);
>>   */
>>  static struct tpm_chip *tpm_chip_find_get(int chip_num)
>>  {
>> -	struct tpm_chip *pos;
>> +	struct tpm_chip *pos, *chip = NULL;
>>
>>  	rcu_read_lock();
>>  	list_for_each_entry_rcu(pos, &tpm_chip_list, list) {
>>     
>
> Crap I even paused for a second when I reviewed the original
> patch.  I think the conversation in my head went something like
> "but will pos be NULL at the end of the loop?"  "Oh, it must".  gah.
>
>   
Yeah, I thought the same and let it pass by..

Rajiv
>>  		if (chip_num != TPM_ANY_NUM && chip_num != pos->dev_num)
>>  			continue;
>>
>> -		if (try_module_get(pos->dev->driver->owner))
>> +		if (try_module_get(pos->dev->driver->owner)) {
>> +			chip = pos;
>>  			break;
>> +		}
>>  	}
>>  	rcu_read_unlock();
>> -	return pos;
>> +	return chip;
>>  }
>>
>>  #define TPM_ORDINAL_PCRREAD cpu_to_be32(21)
>> -- 
>> 1.5.6.3
>>     

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