[PATCH v2] tpm: ibmvtpm: Avoid error message when process gets signal while waiting

[Nageswara Sastry]

On 04/08/21 1:56 am, Stefan Berger wrote:
> From: Stefan Berger <stefanb at linux.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
> TPM_STATUS_BUSY for as long as the vTPM is busy. Since the loop requires
> the TPM's timeouts, get them now using tpm_get_timeouts() after setting
> the TPM2 version flag on the chip.
> 
> Rename the tpm_processing_cmd to tpm_status in ibmvtpm_dev and set the
> TPM_STATUS_BUSY flag while the vTPM is busy processing a command.
> 
> 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 at linux.ibm.com>
> Cc: George Wilson <gcwilson at linux.ibm.com>
> Reported-by: Nageswara R Sastry <rnsastry at linux.ibm.com>
> Signed-off-by: Stefan Berger <stefanb at linux.ibm.com>
> 

Tested-by: Nageswara R Sastry <rnsastry at linux.ibm.com>

Tested the patch applying on kernel version 5.14.0-rc3

1. Ran with recreate commands i.e.
rngd -r /dev/hwrng -t
rngd -r /dev/tpm0 -t

2. Ran the above rngd commands along with "stress-ng - dispatching hogs: 
32 af-alg, 32 bsearch, 32 context, 32 cpu, 32 crypt, 32 hsearch, 32 
longjmp, 32 lsearch, 32 matrix, 32 qsort, 32 str, 32 stream, 32 tsearch, 
32 vecmath, 32 wcs" for 2 hours

Thanks!!
> ---
> 
> v2:
>   - reworded commit text
> ---
>   drivers/char/tpm/tpm_ibmvtpm.c | 31 ++++++++++++++++++-------------
>   drivers/char/tpm/tpm_ibmvtpm.h |  3 ++-
>   2 files changed, 20 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_ibmvtpm.c b/drivers/char/tpm/tpm_ibmvtpm.c
> index 903604769de9..5d795866b483 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) {
> @@ -220,11 +215,12 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
>   		return -EIO;
>   	}
>   
> -	if (ibmvtpm->tpm_processing_cmd) {
> +	if ((ibmvtpm->tpm_status & TPM_STATUS_BUSY)) {
>   		dev_info(ibmvtpm->dev,
>   		         "Need to wait for TPM to finish\n");
>   		/* wait for previous command to finish */
> -		sig = wait_event_interruptible(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
> +		sig = wait_event_interruptible(ibmvtpm->wq,
> +				(ibmvtpm->tpm_status & TPM_STATUS_BUSY) == 0);
>   		if (sig)
>   			return -EINTR;
>   	}
> @@ -237,7 +233,7 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
>   	 * set the processing flag before the Hcall, since we may get the
>   	 * result (interrupt) before even being able to check rc.
>   	 */
> -	ibmvtpm->tpm_processing_cmd = true;
> +	ibmvtpm->tpm_status |= TPM_STATUS_BUSY;
>   
>   again:
>   	rc = ibmvtpm_send_crq(ibmvtpm->vdev,
> @@ -255,7 +251,7 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
>   			goto again;
>   		}
>   		dev_err(ibmvtpm->dev, "tpm_ibmvtpm_send failed rc=%d\n", rc);
> -		ibmvtpm->tpm_processing_cmd = false;
> +		ibmvtpm->tpm_status &= ~TPM_STATUS_BUSY;
>   	}
>   
>   	spin_unlock(&ibmvtpm->rtce_lock);
> @@ -269,7 +265,9 @@ 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_status;
>   }
>   
>   /**
> @@ -457,7 +455,7 @@ 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 = TPM_STATUS_BUSY,
>   	.req_complete_val = 0,
>   	.req_canceled = tpm_ibmvtpm_req_canceled,
>   };
> @@ -550,7 +548,7 @@ static void ibmvtpm_crq_process(struct ibmvtpm_crq *crq,
>   		case VTPM_TPM_COMMAND_RES:
>   			/* len of the data in rtce buffer */
>   			ibmvtpm->res_len = be16_to_cpu(crq->len);
> -			ibmvtpm->tpm_processing_cmd = false;
> +			ibmvtpm->tpm_status &= ~TPM_STATUS_BUSY;
>   			wake_up_interruptible(&ibmvtpm->wq);
>   			return;
>   		default:
> @@ -688,8 +686,15 @@ 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..252f1cccdfc5 100644
> --- a/drivers/char/tpm/tpm_ibmvtpm.h
> +++ b/drivers/char/tpm/tpm_ibmvtpm.h
> @@ -41,7 +41,8 @@ struct ibmvtpm_dev {
>   	wait_queue_head_t wq;
>   	u16 res_len;
>   	u32 vtpm_version;
> -	bool tpm_processing_cmd;
> +	u8 tpm_status;
> +#define TPM_STATUS_BUSY		(1 << 0) /* vtpm is processing a command */
>   };
>   
>   #define CRQ_RES_BUF_SIZE	PAGE_SIZE
> 

-- 
Thanks and Regards
R.Nageswara Sastry