tpm_i2c_nuvoton: fix potential buffer overruns caused by bit glitches on the bus

BugLink: http://bugs.launchpad.net/bugs/1755179
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>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/drivers/char/tpm/tpm_i2c_nuvoton.c b/drivers/char/tpm/tpm_i2c_nuvoton.c
index c6428771841f814a891719fab16e92d7e0723fc7..caa86b19c76dd7007a3975756dec8fe069a31db3 100644 (file)
--- 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;