linux-kernel - Re: [PATCH v9 14/17] tpm: remove TPM_TRANSMIT

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Message-ID: <20181118195104.GA21938@ziepe.ca>
Date:   Sun, 18 Nov 2018 12:51:04 -0700
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        Tomas Winkler <tomas.winkler@...el.com>,
        Tadeusz Struk <tadeusz.struk@...el.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Nayna Jain <nayna@...ux.ibm.com>,
        Peter Huewe <peterhuewe@....de>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 14/17] tpm: remove TPM_TRANSMIT_UNLOCKED flag

On Sun, Nov 18, 2018 at 02:47:47PM +0200, Jarkko Sakkinen wrote:
> Added locking as part of tpm_try_get_ops() and tpm_put_ops() as they are
> anyway used in most of the call sites except in tpmrm_release() where we
> take the locks manually.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> Reviewed-by: Stefan Berger <stefanb@...ux.ibm.com>
> ---
>  drivers/char/tpm/tpm-chip.c       |  2 ++
>  drivers/char/tpm/tpm-dev-common.c |  4 +---
>  drivers/char/tpm/tpm-interface.c  |  8 --------
>  drivers/char/tpm/tpm.h            |  8 ++------
>  drivers/char/tpm/tpm2-cmd.c       | 13 ++++---------
>  drivers/char/tpm/tpm2-space.c     | 15 ++++++---------
>  6 files changed, 15 insertions(+), 35 deletions(-)
 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 32db84683c40..157505b0f755 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -58,6 +58,7 @@ int tpm_try_get_ops(struct tpm_chip *chip)
>  	if (!chip->ops)
>  		goto out_lock;
>  
> +	mutex_lock(&chip->tpm_mutex);
>  	return 0;

It really isn't appropriate for something called 'get' to be exclusive
like this.. Call it tpm_try_lock_ops() ?

> diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
> index c7dc54930576..582caefcf19b 100644
> --- a/drivers/char/tpm/tpm-dev-common.c
> +++ b/drivers/char/tpm/tpm-dev-common.c
> @@ -33,7 +33,6 @@ static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
>  	struct tpm_header *header = (void *)buf;
>  	ssize_t ret, len;
>  
> -	mutex_lock(&chip->tpm_mutex);

The now implicit locking should be tested for using lockdep calls in
all places that assume the lock is held by the caller.

Jason