Subject: Re: [PATCH v4 06/15] smack: Refactor to remove bprm_secureexec hook
To: Kees Cook <keescook@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>
Cc: David Howells <dhowells@redhat.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        John Johansen <john.johansen@canonical.com>,
        "Serge E. Hallyn" <serge@hallyn.com>, Paul Moore <paul@paul-moore.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        James Morris <james.l.morris@oracle.com>,
        Andy Lutomirski <luto@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <1501545093-56634-1-git-send-email-keescook@chromium.org>
 <1501545093-56634-7-git-send-email-keescook@chromium.org>
From: Casey Schaufler <casey@schaufler-ca.com>
Message-ID: <8bbffc76-5142-8018-569b-7e954cbac75a@schaufler-ca.com>
Date: Tue, 1 Aug 2017 08:24:55 -0700
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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@schaufler-ca.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> Acked-by: Serge Hallyn <serge@hallyn.com>

Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>

> ---
>  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),