linux-kernel - Re: [PATCH] tpm/tpm_tis: Free IRQ if probing fails

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Message-ID: <d6684575-ce91-fe72-6035-11834a05cd54@redhat.com>
Date:   Tue, 14 Apr 2020 10:26:32 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-integrity@...r.kernel.org, stable@...r.kernel.org,
        Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm/tpm_tis: Free IRQ if probing fails

Hi,

On 4/14/20 9:13 AM, Jarkko Sakkinen wrote:
> On Mon, Apr 13, 2020 at 08:11:15PM +0200, Hans de Goede wrote:
>> Hi,
>>
>> On 4/13/20 8:07 PM, Jarkko Sakkinen wrote:
>>> On Mon, Apr 13, 2020 at 12:04:25PM +0200, Hans de Goede wrote:
>>>> Hi Jarkko,
>>>>
>>>> On 4/12/20 7:04 PM, Jarkko Sakkinen wrote:
>>>>> Call devm_free_irq() if we have to revert to polling in order not to
>>>>> unnecessarily reserve the IRQ for the life-cycle of the driver.
>>>>>
>>>>> Cc: stable@...r.kernel.org # 4.5.x
>>>>> Reported-by: Hans de Goede <hdegoede@...hat.com>
>>>>> Fixes: e3837e74a06d ("tpm_tis: Refactor the interrupt setup")
>>>>> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
>>>>> ---
>>>>>     drivers/char/tpm/tpm_tis_core.c | 5 ++++-
>>>>>     1 file changed, 4 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
>>>>> index 27c6ca031e23..ae6868e7b696 100644
>>>>> --- a/drivers/char/tpm/tpm_tis_core.c
>>>>> +++ b/drivers/char/tpm/tpm_tis_core.c
>>>>> @@ -1062,9 +1062,12 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>>>>>     		if (irq) {
>>>>>     			tpm_tis_probe_irq_single(chip, intmask, IRQF_SHARED,
>>>>>     						 irq);
>>>>> -			if (!(chip->flags & TPM_CHIP_FLAG_IRQ))
>>>>> +			if (!(chip->flags & TPM_CHIP_FLAG_IRQ)) {
>>>>>     				dev_err(&chip->dev, FW_BUG
>>>>>     					"TPM interrupt not working, polling instead\n");
>>>>> +				devm_free_irq(chip->dev.parent, priv->irq,
>>>>> +					      chip);
>>>>> +			}
>>>>
>>>> My initial plan was actually to do something similar, but if the probe code
>>>> is actually ever fixed to work as intended again then this will lead to a
>>>> double free as then the IRQ-test path of tpm_tis_send() will have called
>>>> disable_interrupts() which already calls devm_free_irq().
>>>>
>>>> You could check for chip->irq != 0 here to avoid that.

Erm in case you haven't figured it out yet this should be priv->irq != 0, sorry.

>>>>
>>>> But it all is rather messy, which is why I went with the "#if 0" approach
>>>> in my patch.
>>>
>>> I think it is right way to fix it. It is a bug independent of the issue
>>> we are experiencing.
>>>
>>> However, what you are suggesting should be done in addition. Do you have
>>> a patch in place or do you want me to refine mine?
>>
>> I do not have a patch ready for this, if you can refine yours that would
>> be great.
> 
> Thanks! Just wanted to confirm.

And thank you for working on a (temporary?) fix for this.

Regards,

Hans