Re: [PATCH] tpm: Check the bios_dir entry for NULL before accessing it

[Stefan Berger <stefanb-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>]

On 11/16/2016 10:40 AM, Jarkko Sakkinen wrote:
> On Wed, Nov 16, 2016 at 08:28:30PM +0530, Nayna wrote:
>>
>> On 11/16/2016 07:26 PM, Stefan Berger wrote:
>>> Check the bios_dir entry for NULL before accessing it. Currently
>>> this crashes the driver when a TPM 2 is attached and the entries
>>> are NULL.
>> Thanks Stefan !! I think it would be good to also add Fixes in commit
>> description here.
>>
>> Fixes: d660a91a1b9d (tpm: adds NULL check for securityfs pseudo files)
> Not mandatory as this is not in the mainline tree but doesn't hurt
> either.
I wished you could just merge this fix patch into Nayna's original patch 
-- makes bisecting the code a lot easier.

    Stefan

>
> /Jarkko
>
>> Thanks & Regards,
>>    - Nayna
>>
>>> Signed-off-by: Stefan Berger <stefanb-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
>>> ---
>>>    drivers/char/tpm/tpm_eventlog.c | 12 +++++++-----
>>>    1 file changed, 7 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/char/tpm/tpm_eventlog.c b/drivers/char/tpm/tpm_eventlog.c
>>> index ebec4ac..fb603a7 100644
>>> --- a/drivers/char/tpm/tpm_eventlog.c
>>> +++ b/drivers/char/tpm/tpm_eventlog.c
>>> @@ -455,10 +455,12 @@ void tpm_bios_log_teardown(struct tpm_chip *chip)
>>>    	 * This design ensures that open() either safely gets kref or fails.
>>>    	 */
>>>    	for (i = (TPM_NUM_EVENT_LOG_FILES - 1); i >= 0; i--) {
>>> -		inode = d_inode(chip->bios_dir[i]);
>>> -		inode_lock(inode);
>>> -		inode->i_private = NULL;
>>> -		inode_unlock(inode);
>>> -		securityfs_remove(chip->bios_dir[i]);
>>> +		if (chip->bios_dir[i]) {
>>> +			inode = d_inode(chip->bios_dir[i]);
>>> +			inode_lock(inode);
>>> +			inode->i_private = NULL;
>>> +			inode_unlock(inode);
>>> +			securityfs_remove(chip->bios_dir[i]);
>>> +		}
>>>    	}
>>>    }
>>>


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