tpm: Address !chip->auth in tpm_buf_append_hmac_session*()

Unless tpm_chip_bootstrap() was called by the driver, !chip->auth can
cause a null derefence in tpm_buf_hmac_session*().  Thus, address
!chip->auth in tpm_buf_hmac_session*() and remove the fallback
implementation for !TCG_TPM2_HMAC.

Cc: stable@vger.kernel.org # v6.9+
Reported-by: Stefan Berger <stefanb@linux.ibm.com>
Closes: https://lore.kernel.org/linux-integrity/20240617193408.1234365-1-stefanb@linux.ibm.com/
Fixes: 1085b8276bb4 ("tpm: Add the rest of the session HMAC API")
Tested-by: Michael Ellerman <mpe@ellerman.id.au> # ppc
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

1 files changed, 20 insertions, 48 deletions

diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 4d3071e885a0..e93ee8d936a9 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -502,10 +502,6 @@ static inline struct tpm2_auth *tpm2_chip_auth(struct tpm_chip *chip)
 
 void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
 			 u32 handle, u8 *name);
-
-#ifdef CONFIG_TCG_TPM2_HMAC
-
-int tpm2_start_auth_session(struct tpm_chip *chip);
 void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
 				 u8 attributes, u8 *passphrase,
 				 int passphraselen);
@@ -515,9 +511,27 @@ static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
 						   u8 *passphrase,
 						   int passphraselen)
 {
-	tpm_buf_append_hmac_session(chip, buf, attributes, passphrase,
-				    passphraselen);
+	struct tpm_header *head;
+	int offset;
+
+	if (tpm2_chip_auth(chip)) {
+		tpm_buf_append_hmac_session(chip, buf, attributes, passphrase, passphraselen);
+	} else  {
+		offset = buf->handles * 4 + TPM_HEADER_SIZE;
+		head = (struct tpm_header *)buf->data;
+
+		/*
+		 * If the only sessions are optional, the command tag must change to
+		 * TPM2_ST_NO_SESSIONS.
+		 */
+		if (tpm_buf_length(buf) == offset)
+			head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
+	}
 }
+
+#ifdef CONFIG_TCG_TPM2_HMAC
+
+int tpm2_start_auth_session(struct tpm_chip *chip);
 void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf);
 int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
 				int rc);
@@ -532,48 +546,6 @@ static inline int tpm2_start_auth_session(struct tpm_chip *chip)
 static inline void tpm2_end_auth_session(struct tpm_chip *chip)
 {
 }
-static inline void tpm_buf_append_hmac_session(struct tpm_chip *chip,
-					       struct tpm_buf *buf,
-					       u8 attributes, u8 *passphrase,
-					       int passphraselen)
-{
-	/* offset tells us where the sessions area begins */
-	int offset = buf->handles * 4 + TPM_HEADER_SIZE;
-	u32 len = 9 + passphraselen;
-
-	if (tpm_buf_length(buf) != offset) {
-		/* not the first session so update the existing length */
-		len += get_unaligned_be32(&buf->data[offset]);
-		put_unaligned_be32(len, &buf->data[offset]);
-	} else {
-		tpm_buf_append_u32(buf, len);
-	}
-	/* auth handle */
-	tpm_buf_append_u32(buf, TPM2_RS_PW);
-	/* nonce */
-	tpm_buf_append_u16(buf, 0);
-	/* attributes */
-	tpm_buf_append_u8(buf, 0);
-	/* passphrase */
-	tpm_buf_append_u16(buf, passphraselen);
-	tpm_buf_append(buf, passphrase, passphraselen);
-}
-static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
-						   struct tpm_buf *buf,
-						   u8 attributes,
-						   u8 *passphrase,
-						   int passphraselen)
-{
-	int offset = buf->handles * 4 + TPM_HEADER_SIZE;
-	struct tpm_header *head = (struct tpm_header *) buf->data;
-
-	/*
-	 * if the only sessions are optional, the command tag
-	 * must change to TPM2_ST_NO_SESSIONS
-	 */
-	if (tpm_buf_length(buf) == offset)
-		head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
-}
 static inline void tpm_buf_fill_hmac_session(struct tpm_chip *chip,
 					     struct tpm_buf *buf)
 {