Re: [tpmdd-devel] [PATCH RFC v2 3/5] tpm: infrastructure for TPM spaces

From: James Bottomley <jejb@linux.vnet.ibm.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	tpmdd-devel@lists.sourceforge.net
Cc: open list <linux-kernel@vger.kernel.org>,
	linux-security-module@vger.kernel.org
Subject: Re: [tpmdd-devel] [PATCH RFC v2 3/5] tpm: infrastructure for TPM spaces
Date: Thu, 12 Jan 2017 12:38:52 -0800	[thread overview]
Message-ID: <1484253532.5807.16.camel@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170112174612.9314-4-jarkko.sakkinen@linux.intel.com>

On Thu, 2017-01-12 at 19:46 +0200, Jarkko Sakkinen wrote:
> +static int tpm2_map_response(struct tpm_chip *chip, u32 cc, u8 *rsp,
> size_t len)
> +{
> +       struct tpm_space *space = &chip->work_space;
> +       u32 phandle;
> +       u32 vhandle;
> +       u32 attrs;
> +       int i;
> +       int rc;
> +
> +       if (!tpm2_find_cc_attrs(chip, cc, &attrs)) {
> +               /* should never happen */
> +               dev_err(&chip->dev, "TPM returned a different CC:
> 0x%04x\n",
> +                       cc);
> +               rc = -EFAULT;
> +               goto out_err;
> +       }
> +
> +       if (!((attrs >> TPM2_CC_ATTR_RHANDLE) & 1))
> +               return 0;
> +
> +       phandle = be32_to_cpup((__be32 *)&rsp[TPM_HEADER_SIZE]);

I think we have to check the command return code here.  We can't
blindly fish handles out of the response if the TPM returned an error
because they won't exist and we'll pull rubbish from the buffer. 
 Incremental patch below.

Note I think we should use get_unaligned_be32 because we're pulling a
32 bit word from something that's on byte 6 (so misaligned): some
architectures will trigger an unaligned trap for this (it's not a
problem: they trap handle it, it just slows down processing a lot).

James

---

commit d17ad905ff7b114f7efd23f930e9a541ccdf7621
Author: James Bottomley <James.Bottomley@HansenPartnership.com>
Date:   Wed Jan 11 22:01:29 2017 -0800

    check return code

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 61422e6..8009ed4 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -90,6 +90,7 @@ enum tpm2_structures {
 };
 
 enum tpm2_return_codes {
+	TPM2_RC_SUCCESS		= 0x0000,
 	TPM2_RC_HASH		= 0x0083, /* RC_FMT1 */
 	TPM2_RC_HANDLE		= 0x008B,
 	TPM2_RC_INITIALIZE	= 0x0100, /* RC_VER1 */
diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index ca55feb..44e5501 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -16,6 +16,7 @@
  */
 
 #include <linux/gfp.h>
+#include <asm/unaligned.h>
 #include "tpm.h"
 
 enum tpm2_handle_types {
@@ -167,9 +168,13 @@ static int tpm2_map_response(struct tpm_chip *chip, u32 cc, u8 *rsp, size_t len)
 	u32 phandle;
 	u32 vhandle;
 	u32 attrs;
+	u32 return_code = get_unaligned_be32((__be32 *)&rsp[6]);
 	int i;
 	int rc;
 
+	if (return_code != TPM2_RC_SUCCESS)
+		return 0;
+
 	if (!tpm2_find_cc_attrs(chip, cc, &attrs)) {
 		/* should never happen */
 		dev_err(&chip->dev, "TPM returned a different CC: 0x%04x\n",
