FAILED: patch "[PATCH] tpm: fix response size validation in tpm_get_random()" failed to apply to 4.18-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 84b59f6487d82d3ab4247a099aba66d4d17e8b08 Mon Sep 17 00:00:00 2001
From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Date: Mon, 3 Sep 2018 04:01:26 +0300
Subject: [PATCH] tpm: fix response size validation in tpm_get_random()

When checking whether the response is large enough to be able to contain
the received random bytes in tpm_get_random() and tpm2_get_random(),
they fail to take account the header size, which should be added to the
minimum size. This commit fixes this issue.

Cc: stable@vger.kernel.org
Fixes: c659af78eb7b ("tpm: Check size of response before accessing data")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 1a803b0cf980..318a7078b2ba 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -1321,7 +1321,8 @@ int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max)
 		}
 
 		rlength = be32_to_cpu(tpm_cmd.header.out.length);
-		if (rlength < offsetof(struct tpm_getrandom_out, rng_data) +
+		if (rlength < TPM_HEADER_SIZE +
+			      offsetof(struct tpm_getrandom_out, rng_data) +
 			      recd) {
 			total = -EFAULT;
 			break;
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index c31b490bd41d..3acf4fd4e5a5 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -329,7 +329,9 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 			&buf.data[TPM_HEADER_SIZE];
 		recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
 		if (tpm_buf_length(&buf) <
-		    offsetof(struct tpm2_get_random_out, buffer) + recd) {
+		    TPM_HEADER_SIZE +
+		    offsetof(struct tpm2_get_random_out, buffer) +
+		    recd) {
 			err = -EFAULT;
 			goto out;
 		}