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

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>

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;