linux-kernel - [PATCH] security: keys: trusted: prevent memory leak in error path

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Date:   Wed, 14 Apr 2021 01:13:26 +0500
From:   Muhammad Usama Anjum <musamaanjum@...il.com>
To:     James.Bottomley@...senPartnership.com,
        James Bottomley <jejb@...ux.ibm.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        "open list:KEYS-TRUSTED" <linux-integrity@...r.kernel.org>,
        "open list:KEYS-TRUSTED" <keyrings@...r.kernel.org>,
        "open list:SECURITY SUBSYSTEM" 
        <linux-security-module@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Cc:     musamaanjum@...il.com, kernel-janitors@...r.kernel.org,
        dan.carpenter@...cle.com, colin.king@...onical.com
Subject: [PATCH] security: keys: trusted: prevent memory leak in error path

tpm2_key_decode sometimes allocates blob. This blob should be freed if
some error occurs later in the function. Free the blob before returning
from this function if it was allocated.

Addresses-Coverity: ("Prevent memory leak")
Fixes: 14676f1eb796 ("security: keys: trusted: use ASN.1 TPM2 key format for the blobs")
Signed-off-by: Muhammad Usama Anjum <musamaanjum@...il.com>
---
This is only build tested. 

 security/keys/trusted-keys/trusted_tpm2.c | 37 +++++++++++++++--------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index d225ad140960..4551384124e0 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -378,22 +378,30 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 	}
 
 	/* new format carries keyhandle but old format doesn't */
-	if (!options->keyhandle)
-		return -EINVAL;
+	if (!options->keyhandle) {
+		rc = -EINVAL;
+		goto err;
+	}
 
 	/* must be big enough for at least the two be16 size counts */
-	if (payload->blob_len < 4)
-		return -EINVAL;
+	if (payload->blob_len < 4) {
+		rc = -EINVAL;
+		goto err;
+	}
 
 	private_len = get_unaligned_be16(blob);
 
 	/* must be big enough for following public_len */
-	if (private_len + 2 + 2 > (payload->blob_len))
-		return -E2BIG;
+	if (private_len + 2 + 2 > (payload->blob_len)) {
+		rc = -E2BIG;
+		goto err;
+	}
 
 	public_len = get_unaligned_be16(blob + 2 + private_len);
-	if (private_len + 2 + public_len + 2 > payload->blob_len)
-		return -E2BIG;
+	if (private_len + 2 + public_len + 2 > payload->blob_len) {
+		rc = -E2BIG;
+		goto err;
+	}
 
 	pub = blob + 2 + private_len + 2;
 	/* key attributes are always at offset 4 */
@@ -406,12 +414,14 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 		payload->migratable = 1;
 
 	blob_len = private_len + public_len + 4;
-	if (blob_len > payload->blob_len)
-		return -E2BIG;
+	if (blob_len > payload->blob_len) {
+		rc = -E2BIG;
+		goto err;
+	}
 
 	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
 	if (rc)
-		return rc;
+		goto err;
 
 	tpm_buf_append_u32(&buf, options->keyhandle);
 	tpm2_buf_append_auth(&buf, TPM2_RS_PW,
@@ -433,12 +443,13 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 			(__be32 *) &buf.data[TPM_HEADER_SIZE]);
 
 out:
-	if (blob != payload->blob)
-		kfree(blob);
 	tpm_buf_destroy(&buf);
 
 	if (rc > 0)
 		rc = -EPERM;
+err:
+	if (blob != payload->blob)
+		kfree(blob);
 
 	return rc;
 }
-- 
2.25.1