linux-kernel - [PATCH v2] KEYS: trusted: Fix memory leak in tpm2_key

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Date:   Wed,  8 Jun 2022 21:17:32 +0800
From:   Jianglei Nie <niejianglei2021@....com>
To:     jejb@...ux.ibm.com, jarkko@...nel.org, zohar@...ux.ibm.com,
        dhowells@...hat.com, jmorris@...ei.org, serge@...lyn.com
Cc:     linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Jianglei Nie <niejianglei2021@....com>
Subject: [PATCH v2] KEYS: trusted: Fix memory leak in tpm2_key_encode()

tpm2_key_encode() allocates a memory chunk from scratch with kmalloc(),
but it is never freed, which leads to a memory leak. Free the memory
chunk with kfree() in the return path.

Signed-off-by: Jianglei Nie <niejianglei2021@....com>
---
 security/keys/trusted-keys/trusted_tpm2.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 0165da386289..8b7ab22950d1 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -32,6 +32,7 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 			   struct trusted_key_options *options,
 			   u8 *src, u32 len)
 {
+	int err;
 	const int SCRATCH_SIZE = PAGE_SIZE;
 	u8 *scratch = kmalloc(SCRATCH_SIZE, GFP_KERNEL);
 	u8 *work = scratch, *work1;
@@ -57,8 +58,10 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 		unsigned char bool[3], *w = bool;
 		/* tag 0 is emptyAuth */
 		w = asn1_encode_boolean(w, w + sizeof(bool), true);
-		if (WARN(IS_ERR(w), "BUG: Boolean failed to encode"))
-			return PTR_ERR(w);
+		if (WARN(IS_ERR(w), "BUG: Boolean failed to encode")) {
+			err = PTR_ERR(w);
+			goto out;
+		}
 		work = asn1_encode_tag(work, end_work, 0, bool, w - bool);
 	}
 
@@ -69,8 +72,10 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 	 * trigger, so if it does there's something nefarious going on
 	 */
 	if (WARN(work - scratch + pub_len + priv_len + 14 > SCRATCH_SIZE,
-		 "BUG: scratch buffer is too small"))
-		return -EINVAL;
+		 "BUG: scratch buffer is too small")) {
+		err = -EINVAL;
+		goto out;
+	}
 
 	work = asn1_encode_integer(work, end_work, options->keyhandle);
 	work = asn1_encode_octet_string(work, end_work, pub, pub_len);
@@ -79,10 +84,16 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 	work1 = payload->blob;
 	work1 = asn1_encode_sequence(work1, work1 + sizeof(payload->blob),
 				     scratch, work - scratch);
-	if (WARN(IS_ERR(work1), "BUG: ASN.1 encoder failed"))
-		return PTR_ERR(work1);
+	if (WARN(IS_ERR(work1), "BUG: ASN.1 encoder failed")) {
+		err = -EINVAL;
+		goto out;
+	}
+	kfree(scratch);
 
 	return work1 - payload->blob;
+
+out:
+	return err;
 }
 
 struct tpm2_key_context {
-- 
2.25.1