[PATCH v3] KEYS: trusted: Fix memory leak in tpm2_key_encode()

[Jianglei Nie]

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.

Fixes: f2219745250f ("security: keys: trusted: use ASN.1 TPM2 key format for the blobs")
Signed-off-by: Jianglei Nie <niejianglei2021 at 163.com>
---
 security/keys/trusted-keys/trusted_tpm2.c | 33 ++++++++++++++++-------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 2b2c8eb258d5..eb25c784b5c3 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -32,8 +32,13 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 			   struct trusted_key_options *options,
 			   u8 *src, u32 len)
 {
+	int ret;
 	const int SCRATCH_SIZE = PAGE_SIZE;
-	u8 *scratch = kmalloc(SCRATCH_SIZE, GFP_KERNEL);
+	u8 *scratch;
+
+	scratch = kmalloc(SCRATCH_SIZE, GFP_KERNEL);
+	if (!scratch)
+		return -ENOMEM;
 	u8 *work = scratch, *work1;
 	u8 *end_work = scratch + SCRATCH_SIZE;
 	u8 *priv, *pub;
@@ -47,9 +52,6 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 	pub_len = get_unaligned_be16(src) + 2;
 	pub = src;
 
-	if (!scratch)
-		return -ENOMEM;
-
 	work = asn1_encode_oid(work, end_work, tpm2key_oid,
 			       asn1_oid_len(tpm2key_oid));
 
@@ -57,8 +59,10 @@ 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")) {
+			ret = PTR_ERR(w);
+			goto err;
+		}
 		work = asn1_encode_tag(work, end_work, 0, bool, w - bool);
 	}
 
@@ -69,8 +73,10 @@ 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")) {
+		ret = -EINVAL;
+		goto err;
+	}
 
 	work = asn1_encode_integer(work, end_work, options->keyhandle);
 	work = asn1_encode_octet_string(work, end_work, pub, pub_len);
@@ -79,10 +85,17 @@ 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")) {
+		ret = PTR_ERR(work1);
+		goto err;
+	}
 
+	kfree(scratch);
 	return work1 - payload->blob;
+
+err:
+	kfree(scratch);
+	return ret;
 }
 
 struct tpm2_key_context {
-- 
2.25.1