char/tpm: Fix unitialized usage of data buffer

This patch fixes information leakage to the userspace by initializing
the data buffer to zero.

Reported-by: Peter Huewe <huewe.external@infineon.com>
Signed-off-by: Peter Huewe <huewe.external@infineon.com>
Signed-off-by: Marcel Selhorst <m.selhorst@sirrix.com>
[ Also removed the silly "* sizeof(u8)".  If that isn't 1, we have way
  deeper problems than a simple multiplication can fix.   - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
{
	struct tpm_cmd_t cmd;
	int rc;
	struct tpm_chip *chip;

	chip = tpm_chip_find_get(chip_num);
	if (chip == NULL)
		return -ENODEV;

	cmd.header.in = pcrextend_header;
	cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(pcr_idx);
	memcpy(cmd.params.pcrextend_in.hash, hash, TPM_DIGEST_SIZE);
	rc = transmit_cmd(chip, &cmd, EXTEND_PCR_RESULT_SIZE,
			  "attempting extend a PCR value");

	tpm_chip_put(chip);
	return rc;
}

int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
{
	struct tpm_cmd_t cmd;
	int rc;
	struct tpm_chip *chip;

	chip = tpm_chip_find_get(chip_num);
	if (chip == NULL)
		return -ENODEV;

	cmd.header.in = pcrextend_header;
	cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(pcr_idx);
	memcpy(cmd.params.pcrextend_in.hash, hash, TPM_DIGEST_SIZE);
	rc = transmit_cmd(chip, &cmd, EXTEND_PCR_RESULT_SIZE,
			  "attempting extend a PCR value");

	tpm_chip_put(chip);
	return rc;
}
