Re: [PATCH] KEYS: trusted: fix a couple error pointer dereferences

[Sumit Garg <sumit.garg@xxxxxxxxxx>]

Hi Dan,

On Wed, 14 Apr 2021 at 11:39, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> If registering "reg_shm_out" fails, then it is an error pointer and the
> error handling will call tee_shm_free(reg_shm_out) which leads to an
> error pointer dereference and an Oops.
>
> I've re-arranged it so we only free things that have been allocated
> successfully.
>
> Fixes: 6dd95e650c8a ("KEYS: trusted: Introduce TEE based Trusted Keys")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
>  security/keys/trusted-keys/trusted_tee.c | 24 ++++++++++--------------
>  1 file changed, 10 insertions(+), 14 deletions(-)
>

Thanks for fixing the error path. Although an alternative simple fix
could be [1] but I liked your approach to get rid of redundant "if"
checks. FWIW:

Reviewed-by: Sumit Garg <sumit.garg@xxxxxxxxxx>

[1]

diff --git a/security/keys/trusted-keys/trusted_tee.c
b/security/keys/trusted-keys/trusted_tee.c
index 2ce66c199e1d..c4a54b0fa3eb 100644
--- a/security/keys/trusted-keys/trusted_tee.c
+++ b/security/keys/trusted-keys/trusted_tee.c
@@ -84,6 +84,7 @@ static int trusted_tee_seal(struct
trusted_key_payload *p, char *datablob)
        if (IS_ERR(reg_shm_out)) {
                dev_err(pvt_data.dev, "blob shm register failed\n");
                ret = PTR_ERR(reg_shm_out);
+               reg_shm_out = NULL;
                goto out;
        }

@@ -145,6 +146,7 @@ static int trusted_tee_unseal(struct
trusted_key_payload *p, char *datablob)
        if (IS_ERR(reg_shm_out)) {
                dev_err(pvt_data.dev, "key shm register failed\n");
                ret = PTR_ERR(reg_shm_out);
+               reg_shm_out = NULL;
                goto out;
        }

-Sumit

> diff --git a/security/keys/trusted-keys/trusted_tee.c b/security/keys/trusted-keys/trusted_tee.c
> index 2ce66c199e1d..45f96f6ed673 100644
> --- a/security/keys/trusted-keys/trusted_tee.c
> +++ b/security/keys/trusted-keys/trusted_tee.c
> @@ -65,7 +65,7 @@ static int trusted_tee_seal(struct trusted_key_payload *p, char *datablob)
>         int ret;
>         struct tee_ioctl_invoke_arg inv_arg;
>         struct tee_param param[4];
> -       struct tee_shm *reg_shm_in = NULL, *reg_shm_out = NULL;
> +       struct tee_shm *reg_shm_in, *reg_shm_out;
>
>         memset(&inv_arg, 0, sizeof(inv_arg));
>         memset(&param, 0, sizeof(param));
> @@ -84,7 +84,7 @@ static int trusted_tee_seal(struct trusted_key_payload *p, char *datablob)
>         if (IS_ERR(reg_shm_out)) {
>                 dev_err(pvt_data.dev, "blob shm register failed\n");
>                 ret = PTR_ERR(reg_shm_out);
> -               goto out;
> +               goto free_shm_in;
>         }
>
>         inv_arg.func = TA_CMD_SEAL;
> @@ -109,11 +109,9 @@ static int trusted_tee_seal(struct trusted_key_payload *p, char *datablob)
>                 p->blob_len = param[1].u.memref.size;
>         }
>
> -out:
> -       if (reg_shm_out)
> -               tee_shm_free(reg_shm_out);
> -       if (reg_shm_in)
> -               tee_shm_free(reg_shm_in);
> +       tee_shm_free(reg_shm_out);
> +free_shm_in:
> +       tee_shm_free(reg_shm_in);
>
>         return ret;
>  }
> @@ -126,7 +124,7 @@ static int trusted_tee_unseal(struct trusted_key_payload *p, char *datablob)
>         int ret;
>         struct tee_ioctl_invoke_arg inv_arg;
>         struct tee_param param[4];
> -       struct tee_shm *reg_shm_in = NULL, *reg_shm_out = NULL;
> +       struct tee_shm *reg_shm_in, *reg_shm_out;
>
>         memset(&inv_arg, 0, sizeof(inv_arg));
>         memset(&param, 0, sizeof(param));
> @@ -145,7 +143,7 @@ static int trusted_tee_unseal(struct trusted_key_payload *p, char *datablob)
>         if (IS_ERR(reg_shm_out)) {
>                 dev_err(pvt_data.dev, "key shm register failed\n");
>                 ret = PTR_ERR(reg_shm_out);
> -               goto out;
> +               goto free_shm_in;
>         }
>
>         inv_arg.func = TA_CMD_UNSEAL;
> @@ -170,11 +168,9 @@ static int trusted_tee_unseal(struct trusted_key_payload *p, char *datablob)
>                 p->key_len = param[1].u.memref.size;
>         }
>
> -out:
> -       if (reg_shm_out)
> -               tee_shm_free(reg_shm_out);
> -       if (reg_shm_in)
> -               tee_shm_free(reg_shm_in);
> +       tee_shm_free(reg_shm_out);
> +free_shm_in:
> +       tee_shm_free(reg_shm_in);
>
>         return ret;
>  }
> --
> 2.30.2
>