[PATCH] tpm: Check non-nullity of chip->auth

[Jarkko Sakkinen <jarkko@xxxxxxxxxx>]

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@xxxxxxxxxx/
Cc: Stefan Berger <stefanb@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Fixes: 1085b8276bb4 ("tpm: Add the rest of the session HMAC API")
Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
---
 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;
-- 
2.45.2