Re: [PATCH 4.19 002/106] tpm: Fix TPM 1.2 Shutdown sequence to prevent future TPM operations

[Pavel Machek]

Hi!

> From: Vadim Sukhomlinov <sukhomli...@google.com>
> 
> commit db4d8cb9c9f2af71c4d087817160d866ed572cc9 upstream
> 
> TPM 2.0 Shutdown involve sending TPM2_Shutdown to TPM chip and disabling
> future TPM operations. TPM 1.2 behavior was different, future TPM
> operations weren't disabled, causing rare issues. This patch ensures
> that future TPM operations are disabled.
...

> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -187,12 +187,13 @@ static int tpm_class_shutdown(struct device *dev)
>  {
>       struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);
>  
> +     down_write(&chip->ops_sem);
>       if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> -             down_write(&chip->ops_sem);
>               tpm2_shutdown(chip, TPM2_SU_CLEAR);
>               chip->ops = NULL;
> -             up_write(&chip->ops_sem);
>       }
> +     chip->ops = NULL;
> +     up_write(&chip->ops_sem);
>  
>       return 0;
>  }

Still can be improved -- chip->ops = NULL; is done twice, copy inside
the if {} is redundant...

Best regards,
                                                                        Pavel

-- 
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