linux-kernel - [PATCH v2] tpm: Return the actual size when receiving an unsupported command

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Date:   Wed, 20 Jun 2018 11:55:07 +0200
From:   Ricardo Schwarzmeier <Ricardo.Schwarzmeier@...ineon.com>
To:     <linux-integrity@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <peterhuewe@....de>,
        <jarkko.sakkinen@...ux.intel.com>, <jgg@...pe.ca>, <arnd@...db.de>,
        <gregkh@...uxfoundation.org>,
        Ricardo Schwarzmeier <Ricardo.Schwarzmeier@...ineon.com>
Subject: [PATCH v2] tpm: Return the actual size when receiving an unsupported command

The command size is computed for the header anyway.
It can as well indicate the correct number of bytes to read from the driver.
Fixes: 095531f891e6 ("tpm: return a TPM_RC_COMMAND_CODE response if command is not implemented")

Signed-off-by: Ricardo Schwarzmeier <Ricardo.Schwarzmeier@...ineon.com>
---
 drivers/char/tpm/tpm-interface.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index e32f6e85dc6d..0923e81505a5 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -423,7 +423,7 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
 		header->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
 		header->return_code = cpu_to_be32(TPM2_RC_COMMAND_CODE |
 						  TSS2_RESMGR_TPM_RC_LAYER);
-		return bufsiz;
+		return header->length;
 	}
 
 	if (bufsiz > TPM_BUFSIZE)
-- 
2.17.1