linux-kernel - [PATCH] tpm: fix byte order related arithmetic inconsistency in tpm

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Message-Id: <20170507175002.9558-1-jarkko.sakkinen@linux.intel.com>
Date:   Sun,  7 May 2017 20:50:02 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     tpmdd-devel@...ts.sourceforge.net
Cc:     linux-security-module@...r.kernel.org,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] tpm: fix byte order related arithmetic inconsistency in tpm_getcap()

You should not do arithmetic with __be32 or __le32 types because
sometimes it results incorrect results. Calculations must be done only
with integers that are in in the CPU byte order. This commit migrates
tpm_getcap() to struct tpm_buf in order to sort out these issues.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
---
Now this should work as Robertos patches move byte order conversion
where it should be. Sadly I'm out of reach to my Dell E6400 laptop
that I use for TPM 1.2 testing.
 drivers/char/tpm/tpm-interface.c | 30 ++++++++++++++++--------------
 drivers/char/tpm/tpm.h           | 13 -------------
 2 files changed, 16 insertions(+), 27 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 4ed08ab4d2a8..7436422458c7 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -552,31 +552,33 @@ static const struct tpm_input_header tpm_getcap_header = {
 ssize_t tpm_getcap(struct tpm_chip *chip, u32 subcap_id, cap_t *cap,
 		   const char *desc, size_t min_cap_length)
 {
-	struct tpm_cmd_t tpm_cmd;
+	struct tpm_buf buf;
 	int rc;
 
-	tpm_cmd.header.in = tpm_getcap_header;
+	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_CAP);
+	if (rc)
+		return rc;
+
 	if (subcap_id == TPM_CAP_VERSION_1_1 ||
 	    subcap_id == TPM_CAP_VERSION_1_2) {
-		tpm_cmd.params.getcap_in.cap = cpu_to_be32(subcap_id);
-		/*subcap field not necessary */
-		tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(0);
-		tpm_cmd.header.in.length -= cpu_to_be32(sizeof(__be32));
+		tpm_buf_append_u32(&buf, subcap_id);
+		tpm_buf_append_u32(&buf, 0);
 	} else {
 		if (subcap_id == TPM_CAP_FLAG_PERM ||
 		    subcap_id == TPM_CAP_FLAG_VOL)
-			tpm_cmd.params.getcap_in.cap =
-				cpu_to_be32(TPM_CAP_FLAG);
+			tpm_buf_append_u32(&buf, TPM_CAP_FLAG);
 		else
-			tpm_cmd.params.getcap_in.cap =
-				cpu_to_be32(TPM_CAP_PROP);
-		tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(4);
-		tpm_cmd.params.getcap_in.subcap = cpu_to_be32(subcap_id);
+			tpm_buf_append_u32(&buf, TPM_CAP_PROP);
+
+		tpm_buf_append_u32(&buf, 4);
+		tpm_buf_append_u32(&buf, subcap_id);
 	}
-	rc = tpm_transmit_cmd(chip, NULL, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE,
+	rc = tpm_transmit_cmd(chip, NULL, buf.data, TPM_INTERNAL_RESULT_SIZE,
 			      min_cap_length, 0, desc);
 	if (!rc)
-		*cap = tpm_cmd.params.getcap_out.cap;
+		*cap = *(cap_t *)&buf.data[TPM_HEADER_SIZE + 4];
+
+	tpm_buf_destroy(&buf);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(tpm_getcap);
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index e81d8c7acb39..dd1173427fb2 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -339,17 +339,6 @@ enum tpm_sub_capabilities {
 	TPM_CAP_PROP_TIS_DURATION = 0x120,
 };
 
-struct	tpm_getcap_params_in {
-	__be32	cap;
-	__be32	subcap_size;
-	__be32	subcap;
-} __packed;
-
-struct	tpm_getcap_params_out {
-	__be32	cap_size;
-	cap_t	cap;
-} __packed;
-
 struct	tpm_readpubek_params_out {
 	u8	algorithm[4];
 	u8	encscheme[2];
@@ -399,10 +388,8 @@ struct tpm_startup_in {
 } __packed;
 
 typedef union {
-	struct	tpm_getcap_params_out getcap_out;
 	struct	tpm_readpubek_params_out readpubek_out;
 	u8	readpubek_out_buffer[sizeof(struct tpm_readpubek_params_out)];
-	struct	tpm_getcap_params_in getcap_in;
 	struct	tpm_pcrread_in	pcrread_in;
 	struct	tpm_pcrread_out	pcrread_out;
 	struct	tpm_pcrextend_in pcrextend_in;
-- 
2.11.0