[PATCH 4.4 03/36] tpm_i2c_nuvoton: fix potential buffer overruns caused by bit glitches on the bus

Greg Kroah-Hartman
2018-03-10T00:20:13Z

From: Jeremy Boone <jeremy.boone@nccgroup.trust>

commit f9d4d9b5a5ef2f017bc344fb65a58a902517173b 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>

---
drivers/char/tpm/tpm_i2c_nuvoton.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/char/tpm/tpm_i2c_nuvoton.c
+++ b/drivers/char/tpm/tpm_i2c_nuvoton.c
@@ -267,7 +267,11 @@ static int i2c_nuvoton_recv(struct tpm_c
struct device *dev = chip->dev.parent;
struct i2c_client *client = to_i2c_client(dev);
s32 rc;
- int expected, status, burst_count, retries, size = 0;
+ int status;
+ int burst_count;
+ int retries;
+ int size = 0;
+ u32 expected;

if (count < TPM_HEADER_SIZE) {
i2c_nuvoton_ready(chip); /* return to idle */
@@ -309,7 +313,7 @@ static int i2c_nuvoton_recv(struct tpm_c
* to machine native
*/
expected = be32_to_cpu(*(__be32 *) (buf + 2));
- if (expected > count) {
+ if (expected > count || expected < size) {
dev_err(dev, "%s() expected > count\n", __func__);
size = -EIO;
continue;