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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jeremy Boone <jeremy.boone@nccgroup.trust>,
        James Bottomley <James.Bottomley@HansenPartnership.com>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        James Morris <james.morris@microsoft.com>
Subject: [PATCH 4.4 01/97] tpm: fix potential buffer overruns caused by bit glitches on the bus
Date:   Fri, 23 Mar 2018 10:53:48 +0100
Message-Id: <20180323094157.619109611@linuxfoundation.org>
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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: stable@vger.kernel.org
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-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-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;
 }