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    SubjectRe: [PATCH security-next v3 17/29] LSM: Introduce CONFIG_LSM_ENABLE
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    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@chromium.org>

    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);
    > }
    >
    > /**
    >

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