Re: [PATCH][V2] security: keys: trusted: Fix memory leaks on allocated blob

[Jarkko Sakkinen <jarkko@kernel.org>]

On Mon, Jul 26, 2021 at 12:44:31PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> There are several error return paths that don't kfree the allocated
> blob, leading to memory leaks. Ensure blob is initialized to null as
> some of the error return paths in function tpm2_key_decode do not
> change blob. Add an error return path to kfree blob and use this on
> the current leaky returns.
> 
> Addresses-Coverity: ("Resource leak")
> Fixes: f2219745250f ("security: keys: trusted: use ASN.1 TPM2 key format for the blobs")
> Acked-by: Sumit Garg <sumit.garg@linaro.org>
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> 
> ---
> 
> V2: Add a couple more leaky return path fixes as noted by Sumit Garg
>     Add the if (blob != payload->blob) check on the kfree as
>     noted by Dan Carpenter
> 
> ---
>  security/keys/trusted-keys/trusted_tpm2.c | 39 ++++++++++++++++-------
>  1 file changed, 27 insertions(+), 12 deletions(-)
> 
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index 0165da386289..a2cfdfdf17fa 100644
> --- a/security/keys/trusted-keys/trusted_tpm2.c
> +++ b/security/keys/trusted-keys/trusted_tpm2.c
> @@ -366,7 +366,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
>  	unsigned int private_len;
>  	unsigned int public_len;
>  	unsigned int blob_len;
> -	u8 *blob, *pub;
> +	u8 *blob = NULL, *pub;
>  	int rc;
>  	u32 attrs;
>  
> @@ -378,22 +378,30 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
>  	}
>  
>  	/* new format carries keyhandle but old format doesn't */
> -	if (!options->keyhandle)
> -		return -EINVAL;
> +	if (!options->keyhandle) {
> +		rc = -EINVAL;
> +		goto err;
> +	}
>  
>  	/* must be big enough for at least the two be16 size counts */
> -	if (payload->blob_len < 4)
> -		return -EINVAL;
> +	if (payload->blob_len < 4) {
> +		rc = -EINVAL;
> +		goto err;
> +	}
>  
>  	private_len = get_unaligned_be16(blob);
>  
>  	/* must be big enough for following public_len */
> -	if (private_len + 2 + 2 > (payload->blob_len))
> -		return -E2BIG;
> +	if (private_len + 2 + 2 > (payload->blob_len)) {
> +		rc = -E2BIG;
> +		goto err;
> +	}
>  
>  	public_len = get_unaligned_be16(blob + 2 + private_len);
> -	if (private_len + 2 + public_len + 2 > payload->blob_len)
> -		return -E2BIG;
> +	if (private_len + 2 + public_len + 2 > payload->blob_len) {
> +		rc = -E2BIG;
> +		goto err;
> +	}
>  
>  	pub = blob + 2 + private_len + 2;
>  	/* key attributes are always at offset 4 */
> @@ -406,12 +414,14 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
>  		payload->migratable = 1;
>  
>  	blob_len = private_len + public_len + 4;
> -	if (blob_len > payload->blob_len)
> -		return -E2BIG;
> +	if (blob_len > payload->blob_len) {
> +		rc = -E2BIG;
> +		goto err;
> +	}
>  
>  	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
>  	if (rc)
> -		return rc;
> +		goto err;
>  
>  	tpm_buf_append_u32(&buf, options->keyhandle);
>  	tpm2_buf_append_auth(&buf, TPM2_RS_PW,
> @@ -441,6 +451,11 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
>  		rc = -EPERM;
>  
>  	return rc;
> +
> +err:
> +	if (blob != payload->blob)
> +		kfree(blob);
> +	return rc;
>  }
>  
>  /**
> -- 
> 2.31.1
> 
> 

Just denoting that I saw this, so just response to my other email,
and I'll use this one.

/Jarkko