linux-kernel - [PATCH] tpm: ibmvtpm: Avoid error message when process gets signal while waiting

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Date:   Mon, 12 Jul 2021 12:25:05 -0400
From:   Stefan Berger <stefanb@...ux.vnet.ibm.com>
To:     peterhuewe@....de, jarkko@...nel.org
Cc:     jgg@...pe.ca, 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>,
        Nageswara R Sastry <rnsastry@...ux.ibm.com>
Subject: [PATCH] tpm: ibmvtpm: Avoid error message when process gets signal while waiting

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 configure 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);

The solution is to use wait_event() instead.

To recreat the issue start rngd like this:

sudo rngd -r /dev/hwrng -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>
---
 drivers/char/tpm/tpm_ibmvtpm.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/char/tpm/tpm_ibmvtpm.c b/drivers/char/tpm/tpm_ibmvtpm.c
index 903604769de9..99b0442a5fdf 100644
--- a/drivers/char/tpm/tpm_ibmvtpm.c
+++ b/drivers/char/tpm/tpm_ibmvtpm.c
@@ -106,16 +106,13 @@ 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;
+	wait_event(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
 
 	len = ibmvtpm->res_len;
 
@@ -206,7 +203,7 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
 {
 	struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
 	bool retry = true;
-	int rc, sig;
+	int rc;
 
 	if (!ibmvtpm->rtce_buf) {
 		dev_err(ibmvtpm->dev, "ibmvtpm device is not ready\n");
@@ -224,9 +221,7 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
 		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);
-		if (sig)
-			return -EINTR;
+		wait_event(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
 	}
 
 	spin_lock(&ibmvtpm->rtce_lock);
@@ -551,7 +546,7 @@ static void ibmvtpm_crq_process(struct ibmvtpm_crq *crq,
 			/* len of the data in rtce buffer */
 			ibmvtpm->res_len = be16_to_cpu(crq->len);
 			ibmvtpm->tpm_processing_cmd = false;
-			wake_up_interruptible(&ibmvtpm->wq);
+			wake_up(&ibmvtpm->wq);
 			return;
 		default:
 			return;
-- 
2.31.1