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

BugLink: http://bugs.launchpad.net/bugs/1764762

commit 3be23274 upstream.

Discrete TPMs are often connected over slow serial buses which, on
some platforms, can have glitches causing bit flips.  If a bit does
flip it could cause an overrun if it's in one of the size parameters,
so sanity check that we're not overrunning the provided buffer when
doing a memcpy().
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>
Tested-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/tpm-interface.c

@@ -1057,6 +1057,11 @@ int tpm_get_random(u32 chip_num, u8 *out, size_t max)
 			break;
 
 		recd = be32_to_cpu(tpm_cmd.params.getrandom_out.rng_data_len);
+		if (recd > num_bytes) {
+			total = -EFAULT;
+			break;
+		}
+
 		memcpy(dest, tpm_cmd.params.getrandom_out.rng_data, recd);
 
 		dest += recd;

drivers/char/tpm/tpm2-cmd.c

@@ -668,6 +668,11 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	if (!rc) {
 		data_len = be16_to_cpup(
 			(__be16 *) &buf.data[TPM_HEADER_SIZE + 4]);
+		if (data_len < MIN_KEY_SIZE ||  data_len > MAX_KEY_SIZE + 1) {
+			rc = -EFAULT;
+			goto out;
+		}
+
 		data = &buf.data[TPM_HEADER_SIZE + 6];
 
 		memcpy(payload->key, data, data_len - 1);
@@ -675,6 +680,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 		payload->migratable = data[data_len - 1];
 	}
 
+out:
 	tpm_buf_destroy(&buf);
 	return rc;
 }