From f9d4d9b5a5ef2f017bc344fb65a58a902517173b Mon Sep 17 00:00:00 2001
From: Jeremy Boone <jeremy.boone@nccgroup.trust>
Date: Thu, 8 Feb 2018 12:31:16 -0800
Subject: [PATCH] tpm_i2c_nuvoton: fix potential buffer overruns caused by bit
glitches on the bus
References: bsc#1082555
Patch-mainline: v4.16-rc4
Git-commit: f9d4d9b5a5ef2f017bc344fb65a58a902517173b
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>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
drivers/char/tpm/tpm_i2c_nuvoton.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/char/tpm/tpm_i2c_nuvoton.c b/drivers/char/tpm/tpm_i2c_nuvoton.c
index c6428771841f..caa86b19c76d 100644
--- a/drivers/char/tpm/tpm_i2c_nuvoton.c
+++ b/drivers/char/tpm/tpm_i2c_nuvoton.c
@@ -281,7 +281,11 @@ static int i2c_nuvoton_recv(struct tpm_chip *chip, u8 *buf, size_t count)
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 */
@@ -323,7 +327,7 @@ static int i2c_nuvoton_recv(struct tpm_chip *chip, u8 *buf, size_t count)
* 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;
--
2.13.6