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    Subject[PATCH security-next v5 21/30] LSM: Refactor "security=" in terms of enable/disable
    Date
    For what are marked as the Legacy Major LSMs, make them effectively
    exclusive when selected on the "security=" boot parameter, to handle
    the future case of when a previously major LSMs become non-exclusive
    (e.g. when TOMOYO starts blob-sharing).

    Signed-off-by: Kees Cook <keescook@chromium.org>
    Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
    ---
    security/security.c | 28 ++++++++++++++++++++--------
    1 file changed, 20 insertions(+), 8 deletions(-)

    diff --git a/security/security.c b/security/security.c
    index 1b1ee823457c..2c754968f98b 100644
    --- a/security/security.c
    +++ b/security/security.c
    @@ -129,14 +129,6 @@ static bool __init lsm_allowed(struct lsm_info *lsm)
    if (!is_enabled(lsm))
    return false;

    - /* Skip major-specific checks if not a major LSM. */
    - if ((lsm->flags & LSM_FLAG_LEGACY_MAJOR) == 0)
    - return true;
    -
    - /* Disabled if this LSM isn't the chosen one. */
    - if (strcmp(lsm->name, chosen_major_lsm) != 0)
    - return false;
    -
    return true;
    }

    @@ -191,8 +183,28 @@ static void __init ordered_lsm_init(void)
    ordered_lsms = kcalloc(LSM_COUNT + 1, sizeof(*ordered_lsms),
    GFP_KERNEL);

    + /* Process "security=", if given. */
    if (!chosen_major_lsm)
    chosen_major_lsm = CONFIG_DEFAULT_SECURITY;
    + if (chosen_major_lsm) {
    + struct lsm_info *major;
    +
    + /*
    + * To match the original "security=" behavior, this
    + * explicitly does NOT fallback to another Legacy Major
    + * if the selected one was separately disabled: disable
    + * all non-matching Legacy Major LSMs.
    + */
    + for (major = __start_lsm_info; major < __end_lsm_info;
    + major++) {
    + if ((major->flags & LSM_FLAG_LEGACY_MAJOR) &&
    + strcmp(major->name, chosen_major_lsm) != 0) {
    + set_enabled(major, false);
    + init_debug("security=%s disabled: %s\n",
    + chosen_major_lsm, major->name);
    + }
    + }
    + }

    if (chosen_lsm_order)
    ordered_lsm_parse(chosen_lsm_order, "cmdline");
    --
    2.17.1
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