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SubjectRe: [PATCH] security:trusted_tpm2: Fix memory leak in tpm2_key_encode()
From
Hello Jianglei,

On 08.06.22 04:59, 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.

Repeating my question in your implicit v1:
Are you sure, scratch need not be freed in the successful return case?
asn1_encode_sequence() copies bytes out of scratch into payload->blob,
so it looks like the buffer is unused after function return.

Cheers,
Ahmad

>
> Signed-off-by: Jianglei Nie <niejianglei2021@163.com>
> ---
> security/keys/trusted-keys/trusted_tpm2.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index 0165da386289..dc9efd6c8b14 100644
> --- a/security/keys/trusted-keys/trusted_tpm2.c
> +++ b/security/keys/trusted-keys/trusted_tpm2.c
> @@ -57,8 +57,10 @@ 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"))
> + if (WARN(IS_ERR(w), "BUG: Boolean failed to encode")) {
> + kfree(scratch);
> return PTR_ERR(w);
> + }
> work = asn1_encode_tag(work, end_work, 0, bool, w - bool);
> }
>
> @@ -69,8 +71,10 @@ 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"))
> + "BUG: scratch buffer is too small")) {
> + kfree(scratch);
> return -EINVAL;
> + }
>
> work = asn1_encode_integer(work, end_work, options->keyhandle);
> work = asn1_encode_octet_string(work, end_work, pub, pub_len);
> @@ -79,8 +83,10 @@ 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"))
> + if (WARN(IS_ERR(work1), "BUG: ASN.1 encoder failed")) {
> + kfree(scratch);
> return PTR_ERR(work1);
> + }
>
> return work1 - payload->blob;
> }


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