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

[ Upstream commit 6bb320ca4a4a7b5b3db8c8d7250cc40002046878 ]

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: Sasha Levin <alexander.levin@microsoft.com>

diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
index 5809567d3cf048e0b5b1f5c729a5601f920de29b..d696e5c3d0797726baf82dccb42579eb688b4510 100644 (file)
--- a/drivers/char/tpm/tpm_tis.c
+++ b/drivers/char/tpm/tpm_tis.c
@@ -283,7 +283,8 @@ static int recv_data(struct tpm_chip *chip, u8 *buf, size_t count)
 static int tpm_tis_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;
@@ -298,7 +299,7 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
        }
 
        expected = be32_to_cpu(*(__be32 *) (buf + 2));
-       if (expected > count) {
+       if (expected > count || expected < TPM_HEADER_SIZE) {
                size = -EIO;
                goto out;
        }