linux-kernel - Re: [PATCH v3 05/15] smack: Refactor to remove bprm

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Date:   Tue, 25 Jul 2017 20:58:01 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Casey Schaufler <casey@...aufler-ca.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        John Johansen <john.johansen@...onical.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        James Morris <james.l.morris@...cle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 05/15] smack: Refactor to remove bprm_secureexec hook

On Tue, Jul 18, 2017 at 3:25 PM, Kees Cook <keescook@...omium.org> 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@...aufler-ca.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>

How does this look to you, Casey? I've only got a few unreviewed
patches in this series. Two touch Smack. :)

Thanks!

-Kees

> ---
>  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),
> --
> 2.7.4
>



-- 
Kees Cook
Pixel Security