tpm: Return the actual size when receiving an unsupported command

commit 36a11029b07ee30bdc4553274d0efea645ed9d91 upstream.

The userpace expects to read the number of bytes stated in the header.
Returning the size of the buffer instead would be unexpected.

Cc: stable@vger.kernel.org
Fixes: 095531f891e6 ("tpm: return a TPM_RC_COMMAND_CODE response if command is not implemented")
Signed-off-by: Ricardo Schwarzmeier <Ricardo.Schwarzmeier@infineon.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index dba5259def6038645dbe24d95f0243c0b6282443..86b526b7d990061c2d066944c15d5838955c021c 100644 (file)
--- 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 sizeof(*header);
        }
 
        if (bufsiz > TPM_BUFSIZE)