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

Nageswara Sastry <rnsastry@xxxxxxxxxxxxx> · Wed, 4 Aug 2021 11:00:57 +0530

On 04/08/21 1:56 am, Stefan Berger wrote:
From: Stefan Berger <stefanb@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
Cc: George Wilson <gcwilson@xxxxxxxxxxxxx>
Reported-by: Nageswara R Sastry <rnsastry@xxxxxxxxxxxxx>
Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>


Tested-by: Nageswara R Sastry <rnsastry@xxxxxxxxxxxxx>

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






