All exported functions lack the check for non-nullity of chip->auth. Add
the guard for each.

Link: https://lore.kernel.org/linux-integrity/9f86a167074d9b522311715c567f1c19b88e3ad4.camel@kernel.org/ (local)
Cc: Stefan Berger <stefanb@linux.ibm.com>
Cc: stable@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Fixes: 1085b8276bb4 ("tpm: Add the rest of the session HMAC API")
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
  drivers/char/tpm/tpm2-sessions.c | 26 ++++++++++++++++++++++++--
  1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 907ac9956a78..d833db20531a 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c

@@ -377,6 +377,9 @@ void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
  	u32 len;
  	struct tpm2_auth *auth = chip->auth;
  
+	if (!auth)
+		return;
+
  	/*
  	 * The Architecture Guide requires us to strip trailing zeros
  	 * before computing the HMAC

@@ -449,6 +452,9 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
  	u8 cphash[SHA256_DIGEST_SIZE];
  	struct sha256_state sctx;
  
+	if (!auth)
+		return;
+
  	/* save the command code in BE format */
  	auth->ordinal = head->ordinal;
  

@@ -639,6 +645,9 @@ void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
  	struct tpm2_auth *auth = chip->auth;
  	int slot;
  
+	if (!auth)
+		return;
+
  	slot = (tpm_buf_length(buf) - TPM_HEADER_SIZE)/4;
  	if (slot >= AUTH_MAX_NAMES) {
  		dev_err(&chip->dev, "TPM: too many handles\n");

@@ -705,6 +714,9 @@ int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
  	u32 cc = be32_to_cpu(auth->ordinal);
  	int parm_len, len, i, handles;
  
+	if (!auth)
+		return rc;
+
  	if (auth->session >= TPM_HEADER_SIZE) {
  		WARN(1, "tpm session not filled correctly\n");
  		goto out;

@@ -824,8 +836,13 @@ EXPORT_SYMBOL(tpm_buf_check_hmac_response);
   */
  void tpm2_end_auth_session(struct tpm_chip *chip)
  {
-	tpm2_flush_context(chip, chip->auth->handle);
-	memzero_explicit(chip->auth, sizeof(*chip->auth));
+	struct tpm2_auth *auth = chip->auth;
+
+	if (!auth)
+		return;
+
+	tpm2_flush_context(chip, auth->handle);
+	memzero_explicit(auth, sizeof(*auth));
  }
  EXPORT_SYMBOL(tpm2_end_auth_session);
  

@@ -907,6 +924,11 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
  	int rc;
  	u32 null_key;
  
+	if (!auth) {
+		pr_warn_once("%s: encryption is not active\n", __func__);
+		return 0;
+	}
+
  	rc = tpm2_load_null(chip, &null_key);
  	if (rc)
  		goto out;