linux-kernel - Re: [PATCH] security: keys: trusted: Fix memory leaks on allocated blob

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Message-ID: <CAFA6WYOugaWGj-RoHzikk8L_-vHY6XX8NOKoJL08--Oh4WeM6w@mail.gmail.com>
Date:   Mon, 26 Jul 2021 11:03:10 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Colin King <colin.king@...onical.com>
Cc:     James Bottomley <jejb@...ux.ibm.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        "open list:ASYMMETRIC KEYS" <keyrings@...r.kernel.org>,
        "open list:SECURITY SUBSYSTEM" 
        <linux-security-module@...r.kernel.org>,
        kernel-janitors@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] security: keys: trusted: Fix memory leaks on allocated blob

Hi Colin,

On Fri, 23 Jul 2021 at 22:51, Colin King <colin.king@...onical.com> wrote:
>
> From: Colin Ian King <colin.king@...onical.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.
>

It looks like there are still leaky return paths left such as
tpm_buf_init() failure etc. which needs to be fixed as well.

With that addressed, feel free to add:

Acked-by: Sumit Garg <sumit.garg@...aro.org>

-Sumit

> Addresses-Coverity: ("Resource leak")
> Fixes: f2219745250f ("security: keys: trusted: use ASN.1 TPM2 key format for the blobs")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  security/keys/trusted-keys/trusted_tpm2.c | 30 ++++++++++++++++-------
>  1 file changed, 21 insertions(+), 9 deletions(-)
>
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index 0165da386289..930c67f98611 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 */
> @@ -441,6 +449,10 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
>                 rc = -EPERM;
>
>         return rc;
> +
> +err:
> +       kfree(blob);
> +       return rc;
>  }
>
>  /**
> --
> 2.31.1
>