[PATCH 3.2 36/74] tpm: fix a kernel memory leak in tpm-sysfs.c

[Ben Hutchings]

3.2.94-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>

commit 13b47cfcfc60495cde216eef4c01040d76174cbe upstream.

While cleaning up sysfs callback that prints EK we discovered a kernel
memory leak. This commit fixes the issue by zeroing the buffer used for
TPM command/response.

The leak happen when we use either tpm_vtpm_proxy, tpm_ibmvtpm or
xen-tpmfront.

Fixes: 0883743825e3 ("TPM: sysfs functions consolidation")
Reported-by: Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx>
Tested-by: Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Signed-off-by: James Morris <james.l.morris@xxxxxxxxxx>
[bwh: Backported to 3.2: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/char/tpm/tpm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -879,9 +879,10 @@ ssize_t tpm_show_pubek(struct device *de
 	ssize_t err;
 	int i, rc;
 	char *str = buf;
-
 	struct tpm_chip *chip = dev_get_drvdata(dev);
 
+	memset(&tpm_cmd, 0, sizeof(tpm_cmd));
+
 	tpm_cmd.header.in = tpm_readpubek_header;
 	err = transmit_cmd(chip, &tpm_cmd, READ_PUBEK_RESULT_SIZE,
 			"attempting to read the PUBEK");