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

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

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@vger.kernel.org # 4.5.x
> > Reported-by: Hans de Goede <hdegoede@redhat.com>
> > Fixes: e3837e74a06d ("tpm_tis: Refactor the interrupt setup")
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.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.
> 
> 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?

/Jarkko