[PATCH 4.4 02/36] tpm_i2c_infineon: fix potential buffer overruns caused by bit glitches on the bus

Greg Kroah-Hartman
2018-03-10T00:20:00Z

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

commit 9b8cb28d7c62568a5916bdd7ea1c9176d7f8f2ed 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_infineon.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/char/tpm/tpm_i2c_infineon.c
+++ b/drivers/char/tpm/tpm_i2c_infineon.c
@@ -436,7 +436,8 @@ static int recv_data(struct tpm_chip *ch
static int tpm_tis_i2c_recv(struct tpm_chip *chip, u8 *buf, size_t count)
{
int size = 0;
- int expected, status;
+ int status;
+ u32 expected;

if (count < TPM_HEADER_SIZE) {
size = -EIO;
@@ -451,7 +452,7 @@ static int tpm_tis_i2c_recv(struct tpm_c
}

expected = be32_to_cpu(*(__be32 *)(buf + 2));
- if ((size_t) expected > count) {
+ if (((size_t) expected > count) || (expected < TPM_HEADER_SIZE)) {
size = -EIO;
goto out;
}