linux-kernel - Re: [PATCH 4.19 33/63] tpm: Fix TPM 1.2 Shutdown sequence to prevent future TPM operations

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Message-ID: <20190930061346.GA22914@atrey.karlin.mff.cuni.cz>
Date:   Mon, 30 Sep 2019 08:13:46 +0200
From:   Pavel Machek <pavel@....cz>
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 33/63] tpm: Fix TPM 1.2 Shutdown sequence to prevent
 future TPM operations

> 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.

> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 46caadca916a0..dccc61af9ffab 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -187,12 +187,15 @@ 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);

This is wrong, it takes &chip->ops_sem twice, that can't be
good. db4d8cb9c9f2af71c4d087817160d866ed572cc9 does not have that
problem.

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