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

Jianglei Nie
2022-07-22T08:22:28Z

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@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