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

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Message-ID: <20191008094121.GA608@amd>
Date:   Tue, 8 Oct 2019 11:41:21 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Vadim Sukhomlinov <sukhomlinov@...gle.com>,
        Douglas Anderson <dianders@...omium.org>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 002/106] tpm: Fix TPM 1.2 Shutdown sequence to
 prevent future TPM operations

Hi!

> From: Vadim Sukhomlinov <sukhomlinov@...gle.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

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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