linux-kernel - [PATCH v2 1/4] tpm_tis: Explicitly check for error code

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Date:   Mon, 5 Jun 2023 19:59:56 +0200
From:   Alexander Steffen <Alexander.Steffen@...ineon.com>
To:     <jarkko@...nel.org>, <linux-integrity@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Alexander Steffen <Alexander.Steffen@...ineon.com>
Subject: [PATCH v2 1/4] tpm_tis: Explicitly check for error code

recv_data either returns the number of received bytes, or a negative value
representing an error code. Adding the return value directly to the total
number of received bytes therefore looks a little weird, since it might add
a negative error code to a sum of bytes.

The following check for size < expected usually makes the function return
ETIME in that case, so it does not cause too many problems in practice. But
to make the code look cleaner and because the caller might still be
interested in the original error code, explicitly check for the presence of
an error code and pass that through.

Signed-off-by: Alexander Steffen <Alexander.Steffen@...ineon.com>
---
 drivers/char/tpm/tpm_tis_core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 558144fa707a..aaaa136044ae 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -363,8 +363,13 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 		goto out;
 	}

-	size += recv_data(chip, &buf[TPM_HEADER_SIZE],
-			  expected - TPM_HEADER_SIZE);
+	rc = recv_data(chip, &buf[TPM_HEADER_SIZE],
+		       expected - TPM_HEADER_SIZE);
+	if (rc < 0) {
+		size = rc;
+		goto out;
+	}
+	size += rc;
 	if (size < expected) {
 		dev_err(&chip->dev, "Unable to read remainder of result\n");
 		size = -ETIME;
-- 
2.34.1