linux-kernel - Re: [PATCH] tpm: Fix the driver cleanup code

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Date:   Thu, 21 Dec 2017 13:26:52 -0700
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Azhar Shaikh <azhar.shaikh@...el.com>
Cc:     jarkko.sakkinen@...ux.intel.com, javierm@...hat.com,
        peterhuewe@....de, linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        tpmdd-devel@...ts.sourceforge.net
Subject: Re: [PATCH] tpm: Fix the driver cleanup code

On Thu, Dec 21, 2017 at 12:17:02PM -0800, Azhar Shaikh wrote:
> Commit 3c1701339284353c41 ("tpm: Keep CLKRUN enabled throughout
> the duration of transmit_cmd()") added code which accessed
> chip->ops, even after it was set to NULL in tpm_del_char_device(),
> called from tpm_chip_unregister() in error / driver exit paths.
> So fix this code.
> 
> Fixes: 3c1701339284353c41 ("tpm: Keep CLKRUN enabled throughout
> the duration of transmit_cmd()")
> 
> Suggested-by: Javier Martinez Canillas <javierm@...hat.com>
> Suggested-by: Jason Gunthorpe <jgg@...pe.ca>
> Signed-off-by: Azhar Shaikh <azhar.shaikh@...el.com>
>  drivers/char/tpm/tpm-chip.c     |  5 +++++
>  drivers/char/tpm/tpm.h          |  1 +
>  drivers/char/tpm/tpm_tis.c      |  8 ++------
>  drivers/char/tpm/tpm_tis_core.c | 23 +++++++++++++++--------
>  drivers/char/tpm/tpm_tis_spi.c  |  1 +
>  5 files changed, 24 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 0a62c19937b6..c88ec9a32a7e 100644
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -346,6 +346,10 @@ static void tpm_del_char_device(struct tpm_chip *chip)
>  	down_write(&chip->ops_sem);
>  	if (chip->flags & TPM_CHIP_FLAG_TPM2)
>  		tpm2_shutdown(chip, TPM2_SU_CLEAR);
> +	if (chip->flags & TPM_CHIP_FLAG_DO_NOT_CLEAR_OPS) {
> +		up_write(&chip->ops_sem);
> +		return;
> +	}

Yikes, too ugly. Figure something else out.. ops->clk_enable is always
tpm_tis_clkrun_enable at this point, so maybe call it directly in
the removal path in tpm_tis_core?

Jason