Re: [PATCH] tpm: vtpm_proxy: Do not run tpm2_shutdown

[Stefan Berger]

On 05/25/2017 04:09 PM, Jason Gunthorpe wrote:
> On Thu, May 25, 2017 at 04:04:24PM -0400, Stefan Berger wrote:
> > On 05/25/2017 11:50 AM, Jason Gunthorpe wrote:
> > > On Thu, May 25, 2017 at 09:12:36AM -0400, Stefan Berger wrote:
> > > > The tpm2_shutdown does not work with the VTPM proxy driver since the
> > > > function only gets called when the backend file descriptor is already
> > > > closed and at this point no data can be sent anymore. A proper shutdown
> > > > would have to be initated by a user space application, such as a container
> > > > management stack, that sends the command via the character device before
> > > > terminating the TPM emulator.
> > > >
> > > > To avoid the tpm2_shutdown we introduce a TPM_CHIP_FLAG_NO_SHUTDOWN flag
> > > > that only the VTPM proxy driver sets. This also avoids misleading kernel
> > > > log messages.
> > > This seems strange to me..
> > >
> > > Why isn't ops null if the fd has gone away?
> > >
> > > What is the call flow that hits this?
> > In this function here.
> >
> > static void tpm_del_char_device(struct tpm_chip *chip)
> > {
> >      cdev_device_del(&chip->cdev, &chip->dev);
> >
> >      /* Make the chip unavailable. */
> >      mutex_lock(&idr_lock);
> >      idr_replace(&dev_nums_idr, NULL, chip->dev_num);
> >      mutex_unlock(&idr_lock);
> >
> >      /* Make the driver uncallable. */
> >      down_write(&chip->ops_sem);
> >      if (chip->flags & TPM_CHIP_FLAG_TPM2)
> >          tpm2_shutdown(chip, TPM2_SU_CLEAR);
> >      chip->ops = NULL;
> >      up_write(&chip->ops_sem);
> > }
> >
> > The request cannot be deliver because the anonymous fd has been closed
> > already.
> The driver must always be able to process requests until
> tpm_del_char_device completes, so this is triggering an existing bug
> in vtpm. This change in core behvior is not going to fix the bug.
>
> eg a request from sysfs/etc could come in between vtpm fd closure and
> tpm_del_char_device, and it still must be handled properly.
>
> I guess you need to have transmit command fail fast once the fd is
> closed.

It doesn't hang. Everything is torn down immediately. What is primarily 
annoying are these two log messages:
tpm tpm0: tpm_transmit: tpm_send: error -32
tpm tpm0: transmit returned -32 while stopping the TPM


    Stefan