linux-kernel - [PATCH 4.9 018/164] tpm_crb: check for bad response size

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Message-Id: <20170523200908.133292536@linuxfoundation.org>
Date:   Tue, 23 May 2017 22:07:15 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jerry Snitselaar <jsnitsel@...hat.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Subject: [PATCH 4.9 018/164] tpm_crb: check for bad response size

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

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

From: Jerry Snitselaar <jsnitsel@...hat.com>

commit 8569defde8057258835c51ce01a33de82e14b148 upstream.

Make sure size of response buffer is at least 6 bytes, or
we will underflow and pass large size_t to memcpy_fromio().
This was encountered while testing earlier version of
locality patchset.

Fixes: 30fc8d138e912 ("tpm: TPM 2.0 CRB Interface")
Signed-off-by: Jerry Snitselaar <jsnitsel@...hat.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/char/tpm/tpm_crb.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -111,8 +111,7 @@ static int crb_recv(struct tpm_chip *chi
 
 	memcpy_fromio(buf, priv->rsp, 6);
 	expected = be32_to_cpup((__be32 *) &buf[2]);
-
-	if (expected > count)
+	if (expected > count || expected < 6)
 		return -EIO;
 
 	memcpy_fromio(&buf[6], &priv->rsp[6], expected - 6);