linux-kernel - Re: [PATCH] tpm: Revert "tpm: fix invalid locking in NONBLOCKING mode"

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Message-ID: <20200528003040.GA4781@linux.intel.com>
Date:   Thu, 28 May 2020 03:30:40 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Tadeusz Struk <tstruk@...il.com>
Cc:     James Bottomley <James.Bottomley@...senPartnership.com>,
        Mario Limonciello <mario.limonciello@...l.com>,
        Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jeffrin Jose T <jeffrin@...agiritech.edu.in>,
        Alex Guzman <alex@...man.io>
Subject: Re: [PATCH] tpm: Revert "tpm: fix invalid locking in NONBLOCKING
 mode"

On Tue, May 26, 2020 at 12:39:37PM -0700, Tadeusz Struk wrote:
> On 5/26/20 12:14 PM, James Bottomley wrote:
> > +	/* atomic tpm command send and result receive. We only hold the ops
> > +	 * lock during this period so that the tpm can be unregistered even if
> > +	 * the char dev is held open.
> > +	 */
> > +	if (tpm_try_get_ops(priv->chip)) {
> > +		ret = -EPIPE;
> > +		goto out;
> > +	}
> > +
> Hi James,
> This won't help if the message is read by an async tcti. If the problem lies
> in the chip get locality code, perhaps this could help to debug the root-cause
> instead of masking it out in the upper layer code:

What is TCTI and async TCTI? Not following.

> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 2435216bd10a..da5ecd0376bf 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -202,20 +202,22 @@ static int request_locality(struct tpm_chip *chip, int l)
>  		return rc;
>  
>  	stop = jiffies + chip->timeout_a;
> +	timeout = stop - jiffies;
>  
>  	if (chip->flags & TPM_CHIP_FLAG_IRQ) {
>  again:
>  		timeout = stop - jiffies;
>  		if ((long)timeout <= 0)
> -			return -1;
> +			goto out;
> +
>  		rc = wait_event_interruptible_timeout(priv->int_queue,
> -						      (check_locality
> -						       (chip, l)),
> +						      check_locality(chip, l),
>  						      timeout);
>  		if (rc > 0)
>  			return l;
>  		if (rc == -ERESTARTSYS && freezing(current)) {
>  			clear_thread_flag(TIF_SIGPENDING);
> +			timeout = stop - jiffies;
>  			goto again;
>  		}
>  	} else {
> @@ -226,6 +228,10 @@ static int request_locality(struct tpm_chip *chip, int l)
>  			tpm_msleep(TPM_TIMEOUT);
>  		} while (time_before(jiffies, stop));
>  	}
> +out:
> +	dev_warn(&chip->dev, "%s: failed to request locality %d after %lu ms\n",
> +			 __func__, l, timeout * HZ / 1000);
> +
>  	return -1;
>  }
>  

/Jarkko