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

[Stefan Berger]

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.

    Stefan