Re: [PATCH v4 06/15] smack: Refactor to remove bprm_secureexec hook

[Casey Schaufler]

On 7/31/2017 4:51 PM, Kees Cook wrote:
> The Smack bprm_secureexec hook can be merged with the bprm_set_creds
> hook since it's dealing with the same information, and all of the details
> are finalized during the first call to the bprm_set_creds hook via
> prepare_binprm() (subsequent calls due to binfmt_script, etc, are ignored
> via bprm->called_set_creds).
>
> Here, the test can just happen at the end of the bprm_set_creds hook,
> and the bprm_secureexec hook can be dropped.
>
> Cc: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Acked-by: Serge Hallyn <serge@xxxxxxxxxx>

Reviewed-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>

> ---
>  security/smack/smack_lsm.c | 21 ++++-----------------
>  1 file changed, 4 insertions(+), 17 deletions(-)
>
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 7d4b2e221124..4f1967be3d20 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -950,6 +950,10 @@ static int smack_bprm_set_creds(struct linux_binprm *bprm)
>  	bsp->smk_task = isp->smk_task;
>  	bprm->per_clear |= PER_CLEAR_ON_SETID;
>  
> +	/* Decide if this is a secure exec. */
> +	if (bsp->smk_task != bsp->smk_forked)
> +		bprm->secureexec = 1;
> +
>  	return 0;
>  }
>  
> @@ -967,22 +971,6 @@ static void smack_bprm_committing_creds(struct linux_binprm *bprm)
>  		current->pdeath_signal = 0;
>  }
>  
> -/**
> - * smack_bprm_secureexec - Return the decision to use secureexec.
> - * @bprm: binprm for exec
> - *
> - * Returns 0 on success.
> - */
> -static int smack_bprm_secureexec(struct linux_binprm *bprm)
> -{
> -	struct task_smack *tsp = current_security();
> -
> -	if (tsp->smk_task != tsp->smk_forked)
> -		return 1;
> -
> -	return 0;
> -}
> -
>  /*
>   * Inode hooks
>   */
> @@ -4646,7 +4634,6 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
>  
>  	LSM_HOOK_INIT(bprm_set_creds, smack_bprm_set_creds),
>  	LSM_HOOK_INIT(bprm_committing_creds, smack_bprm_committing_creds),
> -	LSM_HOOK_INIT(bprm_secureexec, smack_bprm_secureexec),
>  
>  	LSM_HOOK_INIT(inode_alloc_security, smack_inode_alloc_security),
>  	LSM_HOOK_INIT(inode_free_security, smack_inode_free_security),