[PATCH 11/18] LSM: Lift LSM selection out of individual LSMs

[Jann Horn]

On Sun, Sep 16, 2018 at 3:14 AM Kees Cook <keescook at chromium.org> wrote:
> In order to adjust LSM selection logic in the future, this moves the
> selection logic up out of the individual LSMs, making their init functions
> only run when actually enabled.
[...]
> +/* Is an LSM allowed to be enabled? */
> +static bool __init lsm_enabled(struct lsm_info *lsm)
> +{
> +       /* Report explicit disabling. */
> +       if (lsm->enabled && !*lsm->enabled) {
> +               pr_info("%s disabled with boot parameter\n", lsm->name);
> +               return false;
> +       }
> +
> +       /* If LSM isn't exclusive, ignore exclusive LSM selection rules. */
> +       if (lsm->type != LSM_TYPE_EXCLUSIVE)
> +               return true;
> +
> +       /* Disabled if another exclusive LSM already selected. */
> +       if (exclusive)
> +               return false;

What is this check for, given that you have the strcmp() just below
here? From a quick look, it (together with everything else that
touches the "exclusive" variable) seems superfluous to me, unless
there are two LSMs with the same name (which really shouldn't happen,
right?).

> +       /* Disabled if this LSM isn't the chosen one. */
> +       if (strcmp(lsm->name, chosen_lsm) != 0)
> +               return false;
> +
> +       return true;
> +}