FAILED: patch "[PATCH] tpm/tpm_crb: Avoid unaligned reads in crb_recv()" failed to apply to 4.9-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.9-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 3d7a850fdc1a2e4d2adbc95cc0fc962974725e88 Mon Sep 17 00:00:00 2001
From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Date: Mon, 4 Feb 2019 15:59:43 +0200
Subject: [PATCH] tpm/tpm_crb: Avoid unaligned reads in crb_recv()

The current approach to read first 6 bytes from the response and then tail
of the response, can cause the 2nd memcpy_fromio() to do an unaligned read
(e.g. read 32-bit word from address aligned to a 16-bits), depending on how
memcpy_fromio() is implemented. If this happens, the read will fail and the
memory controller will fill the read with 1's.

This was triggered by 170d13ca3a2f, which should be probably refined to
check and react to the address alignment. Before that commit, on x86
memcpy_fromio() turned out to be memcpy(). By a luck GCC has done the right
thing (from tpm_crb's perspective) for us so far, but we should not rely on
that. Thus, it makes sense to fix this also in tpm_crb, not least because
the fix can be then backported to stable kernels and make them more robust
when compiled in differing environments.

Cc: stable@vger.kernel.org
Cc: James Morris <jmorris@namei.org>
Cc: Tomas Winkler <tomas.winkler@intel.com>
Cc: Jerry Snitselaar <jsnitsel@redhat.com>
Fixes: 30fc8d138e91 ("tpm: TPM 2.0 CRB Interface")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Acked-by: Tomas Winkler <tomas.winkler@intel.com>

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index 36952ef98f90..763fc7e6c005 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -287,19 +287,29 @@ static int crb_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 	struct crb_priv *priv = dev_get_drvdata(&chip->dev);
 	unsigned int expected;
 
-	/* sanity check */
-	if (count < 6)
+	/* A sanity check that the upper layer wants to get at least the header
+	 * as that is the minimum size for any TPM response.
+	 */
+	if (count < TPM_HEADER_SIZE)
 		return -EIO;
 
+	/* If this bit is set, according to the spec, the TPM is in
+	 * unrecoverable condition.
+	 */
 	if (ioread32(&priv->regs_t->ctrl_sts) & CRB_CTRL_STS_ERROR)
 		return -EIO;
 
-	memcpy_fromio(buf, priv->rsp, 6);
-	expected = be32_to_cpup((__be32 *) &buf[2]);
-	if (expected > count || expected < 6)
+	/* Read the first 8 bytes in order to get the length of the response.
+	 * We read exactly a quad word in order to make sure that the remaining
+	 * reads will be aligned.
+	 */
+	memcpy_fromio(buf, priv->rsp, 8);
+
+	expected = be32_to_cpup((__be32 *)&buf[2]);
+	if (expected > count || expected < TPM_HEADER_SIZE)
 		return -EIO;
 
-	memcpy_fromio(&buf[6], &priv->rsp[6], expected - 6);
+	memcpy_fromio(&buf[8], &priv->rsp[8], expected - 8);
 
 	return expected;
 }