[PATCH 4.4 01/36] tpm: st33zp24: fix potential buffer overruns caused by bit glitches on the bus

Greg Kroah-Hartman
2018-03-10T00:18:17Z

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

commit 6d24cd186d9fead3722108dec1b1c993354645ff 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/st33zp24/st33zp24.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/char/tpm/st33zp24/st33zp24.c
+++ b/drivers/char/tpm/st33zp24/st33zp24.c
@@ -485,7 +485,7 @@ static int st33zp24_recv(struct tpm_chip
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
}

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