On 09/24/2018 05:18 PM, Kees Cook wrote:
> To provide a set of default-enabled LSMs at boot, this introduces the
> new CONFIG_LSM_ENABLE. A value of "all" means all builtin LSMs are
> enabled by default. Any unlisted LSMs will be implicitly disabled
> (excepting those with LSM-specific CONFIGs for enabling/disabling).
>
> The behavior of the LSM-specific CONFIGs for SELinux are AppArmor
> unchanged: the default-enabled state for those LSMs remains controlled
> through their LSM-specific "enable" CONFIGs.
>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
The patch is fine but I am not sure I like the behavior. I much prefer
that its an explicit list and nothing is left to implicit. That is
if there is a conflict between the list and the LSM-specific config
the LSM is disabled.
> ---
> include/linux/lsm_hooks.h | 2 +-
> security/Kconfig | 8 ++++++++
> security/security.c | 4 +++-
> 3 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 95798f212dbf..ab23f1bc6d77 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -2044,7 +2044,7 @@ extern void security_add_hooks(struct security_hook_list *hooks, int count,
> struct lsm_info {
> const char *name; /* Populated automatically. */
> unsigned long flags; /* Optional: flags describing LSM */
> - int *enabled; /* Optional: NULL means enabled. */
> + int *enabled; /* Optional: NULL checks CONFIG_LSM_ENABLE */
> int (*init)(void);
> };
>
> diff --git a/security/Kconfig b/security/Kconfig
> index 27d8b2688f75..71306b046270 100644
> --- a/security/Kconfig
> +++ b/security/Kconfig
> @@ -276,5 +276,13 @@ config DEFAULT_SECURITY
> default "apparmor" if DEFAULT_SECURITY_APPARMOR
> default "" if DEFAULT_SECURITY_DAC
>
> +config LSM_ENABLE
> + string "LSMs to enable at boot time"
> + default "all"
> + help
> + A comma-separate list of LSMs to enable by default at boot. The
> + default is "all", to enable all LSM modules at boot. Any LSMs
> + not listed here will be disabled by default.
> +
> endmenu
>
> diff --git a/security/security.c b/security/security.c
> index a8107d54b3d3..7ecb9879a863 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -45,6 +45,8 @@ char *lsm_names;
> static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
> CONFIG_DEFAULT_SECURITY;
>
> +static __initconst const char * const builtin_lsm_enable = CONFIG_LSM_ENABLE;
> +
> static bool debug __initdata;
> #define init_debug(...) \
> do { \
> @@ -182,7 +184,7 @@ static void __init parse_lsm_enable(const char *str,
> static void __init prepare_lsm_enable(void)
> {
> /* Prepare defaults. */
> - parse_lsm_enable("all", default_enabled, true);
> + parse_lsm_enable(builtin_lsm_enable, default_enabled, true);
> }
>
> /**
>
