[PATCH 4.4 01/97] tpm: fix potential buffer overruns caused by bit glitches on the bus

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

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

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

commit 3be23274755ee85771270a23af7691dc9b3a95db upstream.

Discrete TPMs are often connected over slow serial buses which, on
some platforms, can have glitches causing bit flips.  If a bit does
flip it could cause an overrun if it's in one of the size parameters,
so sanity check that we're not overrunning the provided buffer when
doing a memcpy().

Signed-off-by: Jeremy Boone <jeremy.boone@nccgroup.trust>
Cc: sta...@vger.kernel.org
Signed-off-by: James Bottomley <james.bottom...@hansenpartnership.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>
Signed-off-by: James Morris <james.mor...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/char/tpm/tpm-interface.c |    5 +++++
 drivers/char/tpm/tpm2-cmd.c      |    6 ++++++
 2 files changed, 11 insertions(+)

--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -1040,6 +1040,11 @@ int tpm_get_random(u32 chip_num, u8 *out
                        break;
 
                recd = be32_to_cpu(tpm_cmd.params.getrandom_out.rng_data_len);
+               if (recd > num_bytes) {
+                       total = -EFAULT;
+                       break;
+               }
+
                memcpy(dest, tpm_cmd.params.getrandom_out.rng_data, recd);
 
                dest += recd;
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -622,6 +622,11 @@ static int tpm2_unseal_cmd(struct tpm_ch
        if (!rc) {
                data_len = be16_to_cpup(
                        (__be16 *) &buf.data[TPM_HEADER_SIZE + 4]);
+               if (data_len < MIN_KEY_SIZE ||  data_len > MAX_KEY_SIZE + 1) {
+                       rc = -EFAULT;
+                       goto out;
+               }
+
                data = &buf.data[TPM_HEADER_SIZE + 6];
 
                memcpy(payload->key, data, data_len - 1);
@@ -629,6 +634,7 @@ static int tpm2_unseal_cmd(struct tpm_ch
                payload->migratable = data[data_len - 1];
        }
 
+out:
        tpm_buf_destroy(&buf);
        return rc;
 }