tpm: st33zp24: fix potential buffer overruns caused by bit glitches on the bus

BugLink: http://bugs.launchpad.net/bugs/1764367

commit 6d24cd18 upstream.

Discrete TPMs are often connected over slow serial buses which, on
some platforms, can have glitches causing bit flips.  In all the
driver _recv() functions, we need to use a u32 to unmarshal the
response size, otherwise a bit flip of the 31st bit would cause the
expected variable to go negative, which would then try to read a huge
amount of data.  Also sanity check that the expected amount of data is
large enough for the TPM header.
Signed-off-by: Jeremy Boone <jeremy.boone@nccgroup.trust>
Cc: stable@vger.kernel.org
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: James Morris <james.morris@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/char/tpm/st33zp24/st33zp24.c

@@ -485,7 +485,7 @@ static int st33zp24_recv(struct tpm_chip *chip, unsigned char *buf,
 			    size_t count)
 {
 	int size = 0;
-	int expected;
+	u32 expected;
 
 	if (!chip)
 		return -EBUSY;
@@ -502,7 +502,7 @@ static int st33zp24_recv(struct tpm_chip *chip, unsigned char *buf,
 	}
 
 	expected = be32_to_cpu(*(__be32 *)(buf + 2));
-	if (expected > count) {
+	if (expected > count || expected < TPM_HEADER_SIZE) {
 		size = -EIO;
 		goto out;
 	}