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Subject[PATCH 4.15 012/122] tpm_tis: fix potential buffer overruns caused by bit glitches on the bus
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

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

From: Jeremy Boone <jeremy.boone@nccgroup.trust>

commit 6bb320ca4a4a7b5b3db8c8d7250cc40002046878 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>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.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>

---
drivers/char/tpm/tpm_tis_core.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -202,7 +202,8 @@ static int tpm_tis_recv(struct tpm_chip
{
struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
int size = 0;
- int expected, status;
+ int status;
+ u32 expected;

if (count < TPM_HEADER_SIZE) {
size = -EIO;
@@ -217,7 +218,7 @@ static int tpm_tis_recv(struct tpm_chip
}

expected = be32_to_cpu(*(__be32 *) (buf + 2));
- if (expected > count) {
+ if (expected > count || expected < TPM_HEADER_SIZE) {
size = -EIO;
goto out;
}

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