linux-kernel - Re: [PATCH v4 1/2] tpm: ibmvtpm: Avoid error message when process gets signal while waiting

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Message-ID: <0047b861-c660-e126-a198-ebe77ca3c057@linux.ibm.com>
Date:   Tue, 10 Aug 2021 11:28:15 +0530
From:   Nageswara Sastry <rnsastry@...ux.ibm.com>
To:     Stefan Berger <stefanb@...ux.vnet.ibm.com>, jarkko@...nel.org
Cc:     nasastry@...ibm.com, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Stefan Berger <stefanb@...ux.ibm.com>,
        Nayna Jain <nayna@...ux.ibm.com>,
        George Wilson <gcwilson@...ux.ibm.com>
Subject: Re: [PATCH v4 1/2] tpm: ibmvtpm: Avoid error message when process
 gets signal while waiting



On 10/08/21 12:51 am, Stefan Berger wrote:
> From: Stefan Berger <stefanb@...ux.ibm.com>
> 
> When rngd is run as root then lots of these types of message will appear
> in the kernel log if the TPM has been configured to provide random bytes:
> 
> [ 7406.275163] tpm tpm0: tpm_transmit: tpm_recv: error -4
> 
> The issue is caused by the following call that is interrupted while
> waiting for the TPM's response.
> 
> sig = wait_event_interruptible(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
> 
> Rather than waiting for the response in the low level driver, have it use
> the polling loop in tpm_try_transmit() that uses a command's duration to
> poll until a result has been returned by the TPM, thus ending when the
> timeout has occurred but not responding to signals and ctrl-c anymore. To
> stay in this polling loop extend tpm_ibmvtpm_status() to return
> 'true' for as long as the vTPM is indicated as being busy in
> tpm_processing_cmd. Since the loop requires the TPM's timeouts, get them
> now using tpm_get_timeouts() after setting the TPM2 version flag on the
> chip.
> 
> To recreat the resolved issue start rngd like this:
> 
> sudo rngd -r /dev/hwrng -t
> sudo rngd -r /dev/tpm0 -t
> 
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1981473
> Fixes: 6674ff145eef ("tpm_ibmvtpm: properly handle interrupted packet receptions")
> Cc: Nayna Jain <nayna@...ux.ibm.com>
> Cc: George Wilson <gcwilson@...ux.ibm.com>
> Reported-by: Nageswara R Sastry <rnsastry@...ux.ibm.com>
> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>


Tested-by: Nageswara R Sastry <rnsastry@...ux.ibm.com>

Tested with /dev/hwrng and /dev/tpm0 and not seen any tpm errors from 
the kernel.

> ---
>   drivers/char/tpm/tpm_ibmvtpm.c | 20 ++++++++++++--------
>   drivers/char/tpm/tpm_ibmvtpm.h |  2 +-
>   2 files changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_ibmvtpm.c b/drivers/char/tpm/tpm_ibmvtpm.c
> index 903604769de9..7a9eca5768f8 100644
> --- a/drivers/char/tpm/tpm_ibmvtpm.c
> +++ b/drivers/char/tpm/tpm_ibmvtpm.c
> @@ -106,17 +106,12 @@ static int tpm_ibmvtpm_recv(struct tpm_chip *chip, u8 *buf, size_t count)
>   {
>   	struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
>   	u16 len;
> -	int sig;
>   
>   	if (!ibmvtpm->rtce_buf) {
>   		dev_err(ibmvtpm->dev, "ibmvtpm device is not ready\n");
>   		return 0;
>   	}
>   
> -	sig = wait_event_interruptible(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
> -	if (sig)
> -		return -EINTR;
> -
>   	len = ibmvtpm->res_len;
>   
>   	if (count < len) {
> @@ -269,7 +264,9 @@ static void tpm_ibmvtpm_cancel(struct tpm_chip *chip)
>   
>   static u8 tpm_ibmvtpm_status(struct tpm_chip *chip)
>   {
> -	return 0;
> +	struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
> +
> +	return ibmvtpm->tpm_processing_cmd;
>   }
>   
>   /**
> @@ -457,7 +454,7 @@ static const struct tpm_class_ops tpm_ibmvtpm = {
>   	.send = tpm_ibmvtpm_send,
>   	.cancel = tpm_ibmvtpm_cancel,
>   	.status = tpm_ibmvtpm_status,
> -	.req_complete_mask = 0,
> +	.req_complete_mask = true,
>   	.req_complete_val = 0,
>   	.req_canceled = tpm_ibmvtpm_req_canceled,
>   };
> @@ -688,8 +685,15 @@ static int tpm_ibmvtpm_probe(struct vio_dev *vio_dev,
>   		goto init_irq_cleanup;
>   	}
>   
> -	if (!strcmp(id->compat, "IBM,vtpm20")) {
> +
> +	if (!strcmp(id->compat, "IBM,vtpm20"))
>   		chip->flags |= TPM_CHIP_FLAG_TPM2;
> +
> +	rc = tpm_get_timeouts(chip);
> +	if (rc)
> +		goto init_irq_cleanup;
> +
> +	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
>   		rc = tpm2_get_cc_attrs_tbl(chip);
>   		if (rc)
>   			goto init_irq_cleanup;
> diff --git a/drivers/char/tpm/tpm_ibmvtpm.h b/drivers/char/tpm/tpm_ibmvtpm.h
> index b92aa7d3e93e..51198b137461 100644
> --- a/drivers/char/tpm/tpm_ibmvtpm.h
> +++ b/drivers/char/tpm/tpm_ibmvtpm.h
> @@ -41,7 +41,7 @@ struct ibmvtpm_dev {
>   	wait_queue_head_t wq;
>   	u16 res_len;
>   	u32 vtpm_version;
> -	bool tpm_processing_cmd;
> +	u8 tpm_processing_cmd;
>   };
>   
>   #define CRQ_RES_BUF_SIZE	PAGE_SIZE
> 

-- 
Thanks and Regards
R.Nageswara Sastry