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From:   Stefan Berger <stefanb@linux.vnet.ibm.com>
To:     jarkko@kernel.org
Cc:     nasastry@in.ibm.com, linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Stefan Berger <stefanb@linux.ibm.com>,
        Nayna Jain <nayna@linux.ibm.com>,
        George Wilson <gcwilson@linux.ibm.com>,
        Nageswara R Sastry <rnsastry@linux.ibm.com>
Subject: [PATCH v4 1/2] tpm: ibmvtpm: Avoid error message when process gets signal while waiting
Date:   Mon,  9 Aug 2021 15:21:58 -0400
Message-Id: <20210809192159.2176580-2-stefanb@linux.vnet.ibm.com>
In-Reply-To: <20210809192159.2176580-1-stefanb@linux.vnet.ibm.com>
References: <20210809192159.2176580-1-stefanb@linux.vnet.ibm.com>
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From: Stefan Berger <stefanb@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
'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@linux.ibm.com>
Cc: George Wilson <gcwilson@linux.ibm.com>
Reported-by: Nageswara R Sastry <rnsastry@linux.ibm.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 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
-- 
2.31.1