linux-kernel - Re: [PATCH v3] tpm: Restore functionality to xen vtpm driver.

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Message-ID: <20180918185952.GA26508@linux.intel.com>
Date:   Tue, 18 Sep 2018 21:59:52 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     peterhuewe@....de, jgg@...pe.ca, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        jgross@...e.com, dunlapg@...ch.edu,
        "Dr. Greg Wettstein" <greg@...d.enjellic.com>,
        "Dr . Greg Wettstein" <greg@...ellic.com>, stable@...r.kernel.org
Subject: Re: [PATCH v3] tpm: Restore functionality to xen vtpm driver.

On Mon, Sep 17, 2018 at 06:53:33PM -0400, Boris Ostrovsky wrote:
> From: "Dr. Greg Wettstein" <greg@...d.enjellic.com>
> 
> Functionality of the xen-tpmfront driver was lost secondary to
> the introduction of xenbus multi-page support in commit ccc9d90a9a8b
> ("xenbus_client: Extend interface to support multi-page ring").
> 
> In this commit pointer to location of where the shared page address
> is stored was being passed to the xenbus_grant_ring() function rather
> then the address of the shared page itself. This resulted in a situation
> where the driver would attach to the vtpm-stubdom but any attempt
> to send a command to the stub domain would timeout.
> 
> A diagnostic finding for this regression is the following error
> message being generated when the xen-tpmfront driver probes for a
> device:
> 
> <3>vtpm vtpm-0: tpm_transmit: tpm_send: error -62
> 
> <3>vtpm vtpm-0: A TPM error (-62) occurred attempting to determine
> the timeouts
> 
> This fix is relevant to all kernels from 4.1 forward which is the
> release in which multi-page xenbus support was introduced.
> 
> Daniel De Graaf formulated the fix by code inspection after the
> regression point was located.
> 
> Fixes: ccc9d90a9a8b ("xenbus_client: Extend interface to support multi-page ring")
> Signed-off-by: Dr. Greg Wettstein <greg@...ellic.com>
> 
> [boris: Updated commit message, added Fixes tag]
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Cc: stable@...r.kernel.org # v4.1+
> ---
>  drivers/char/tpm/xen-tpmfront.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/char/tpm/xen-tpmfront.c b/drivers/char/tpm/xen-tpmfront.c
> index 911475d36800..b150f87f38f5 100644
> --- a/drivers/char/tpm/xen-tpmfront.c
> +++ b/drivers/char/tpm/xen-tpmfront.c
> @@ -264,7 +264,7 @@ static int setup_ring(struct xenbus_device *dev, struct tpm_private *priv)
>  		return -ENOMEM;
>  	}
>  
> -	rv = xenbus_grant_ring(dev, &priv->shr, 1, &gref);
> +	rv = xenbus_grant_ring(dev, priv->shr, 1, &gref);
>  	if (rv < 0)
>  		return rv;
>  
> -- 
> 2.17.1
> 

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

/Jarkko