linux-kernel - [PATCH 3.16 297/410] tpm_i2c_infineon: fix potential buffer overruns caused by bit glitches on the bus

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Message-ID: <lsq.1528380321.379136185@decadent.org.uk>
Date:   Thu, 07 Jun 2018 15:05:21 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "James Morris" <james.morris@...rosoft.com>,
        "James Bottomley" <James.Bottomley@...senPartnership.com>,
        "Jeremy Boone" <jeremy.boone@...group.trust>,
        "Jarkko Sakkinen" <jarkko.sakkinen@...ux.intel.com>
Subject: [PATCH 3.16 297/410] tpm_i2c_infineon: fix potential buffer
 overruns caused by bit glitches on the bus

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jeremy Boone <jeremy.boone@...group.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@...group.trust>
Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Signed-off-by: James Morris <james.morris@...rosoft.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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;
 	}