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From: Greg KH <greg@kroah.com>
To: Jarkko Sakkinen <jarkko@kernel.org>
Cc: linux-integrity@vger.kernel.org, stable@vger.kernel.org,
	Hans de Goede <hdegoede@redhat.com>,
	Peter Huewe <peterhuewe@gmx.de>, Jason Gunthorpe <jgg@ziepe.ca>,
	James Bottomley <James.Bottomley@hansenpartnership.com>
Subject: Re: [PATCH v2] tpm: Replace WARN_ONCE() with dev_err_once() in tpm_tis_status()
Date: Mon, 31 May 2021 07:50:41 +0200	[thread overview]
Message-ID: <YLR5MSiVpv52FcZe@kroah.com> (raw)
In-Reply-To: <20210531053427.118552-1-jarkko@kernel.org>

On Mon, May 31, 2021 at 08:34:27AM +0300, Jarkko Sakkinen wrote:
> Do not torn down the system when getting invalid status from a TPM chip.
> This can happen when panic-on-warn is used.
> 
> In addition, print out the value of TPM_STS.x instead of "invalid
> status". In order to get the earlier benefits for forensics, also call
> dump_stack().
> 
> Link: https://lore.kernel.org/keyrings/YKzlTR1AzUigShtZ@kroah.com/
> Fixes: 55707d531af6 ("tpm_tis: Add a check for invalid status")
> Cc: stable@vger.kernel.org
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Greg KH <greg@kroah.com>
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> 
> v2:
> Dump also stack only once.

Huh?

> 
>  drivers/char/tpm/tpm_tis_core.c | 28 ++++++++++++++++++++--------
>  1 file changed, 20 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 55b9d3965ae1..ce410f19eff2 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -188,21 +188,33 @@ static int request_locality(struct tpm_chip *chip, int l)
>  static u8 tpm_tis_status(struct tpm_chip *chip)
>  {
>  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> -	int rc;
> +	static unsigned long klog_once;
>  	u8 status;
> +	int rc;
>  
>  	rc = tpm_tis_read8(priv, TPM_STS(priv->locality), &status);
>  	if (rc < 0)
>  		return 0;
>  
>  	if (unlikely((status & TPM_STS_READ_ZERO) != 0)) {
> -		/*
> -		 * If this trips, the chances are the read is
> -		 * returning 0xff because the locality hasn't been
> -		 * acquired.  Usually because tpm_try_get_ops() hasn't
> -		 * been called before doing a TPM operation.
> -		 */
> -		WARN_ONCE(1, "TPM returned invalid status\n");
> +		if  (!test_and_set_bit(BIT(0), &klog_once)) {

Odd whitespace...

Anyway, why?  Isn't this what the ratelimit stuff should give you?  How
badly is this being tripped so much so that you need to only do this
once per entire system and not per-device?

thanks,

greg k-h

  reply	other threads:[~2021-05-31  5:50 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-31  5:34 [PATCH v2] tpm: Replace WARN_ONCE() with dev_err_once() in tpm_tis_status() Jarkko Sakkinen
2021-05-31  5:50 ` Greg KH [this message]
2021-06-01 17:43   ` Jarkko Sakkinen

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