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

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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>
This commit is contained in:
Jeremy Boone 2018-02-08 12:31:16 -08:00 committed by James Morris
parent 6bb320ca4a
commit f9d4d9b5a5
1 changed files with 6 additions and 2 deletions
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8
drivers/char/tpm/tpm_i2c_nuvoton.c
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@ -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;