Re: [PATCH v2] KEYS: trusted: Fix memory leak in tpm2_key_encode()

Jonathan McDowell
2022-06-08T13:38:45Z

On Wed, Jun 08, 2022 at 09:17:32PM +0800, Jianglei Nie wrote:
> 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.

This change only does the kfree in the success path; "out" just returns
the error without freeing the memory.

> Signed-off-by: Jianglei Nie <niejianglei2021@163.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