From: James Morris <jmorris@xxxxxxxxx> commit dd0859dccbe291cf8179a96390f5c0e45cb9af1d upstream. Subsequent patches will add RO hardening to LSM hooks, however, SELinux still needs to be able to perform runtime disablement after init to handle architectures where init-time disablement via boot parameters is not feasible. Introduce a new kernel configuration parameter CONFIG_SECURITY_WRITABLE_HOOKS, and a helper macro __lsm_ro_after_init, to handle this case. Signed-off-by: James Morris <james.l.morris@xxxxxxxxxx> Acked-by: Stephen Smalley <sds@xxxxxxxxxxxxx> Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx> Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Alexander Grund <git@xxxxxxxxxx> --- include/linux/lsm_hooks.h | 7 +++++++ security/Kconfig | 5 +++++ security/selinux/Kconfig | 6 ++++++ 3 files changed, 18 insertions(+) diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 53ac461f342b..65dfda2623c2 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -1921,6 +1921,13 @@ static inline void security_delete_hooks(struct security_hook_list *hooks, } #endif /* CONFIG_SECURITY_SELINUX_DISABLE */ +/* Currently required to handle SELinux runtime hook disable. */ +#ifdef CONFIG_SECURITY_WRITABLE_HOOKS +#define __lsm_ro_after_init +#else +#define __lsm_ro_after_init __ro_after_init +#endif /* CONFIG_SECURITY_WRITABLE_HOOKS */ + extern int __init security_module_enable(const char *module); extern void __init capability_add_hooks(void); #ifdef CONFIG_SECURITY_YAMA diff --git a/security/Kconfig b/security/Kconfig index 32f36b40e9f0..7d6edc5829a1 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -31,6 +31,11 @@ config SECURITY If you are unsure how to answer this question, answer N. +config SECURITY_WRITABLE_HOOKS + depends on SECURITY + bool + default n + config PAGE_TABLE_ISOLATION bool "Remove the kernel mapping in user mode" default y diff --git a/security/selinux/Kconfig b/security/selinux/Kconfig index ea7e3efbe0f7..8af7a690eb40 100644 --- a/security/selinux/Kconfig +++ b/security/selinux/Kconfig @@ -40,6 +40,7 @@ config SECURITY_SELINUX_BOOTPARAM_VALUE config SECURITY_SELINUX_DISABLE bool "NSA SELinux runtime disable" depends on SECURITY_SELINUX + select SECURITY_WRITABLE_HOOKS default n help This option enables writing to a selinuxfs node 'disable', which @@ -50,6 +51,11 @@ config SECURITY_SELINUX_DISABLE portability across platforms where boot parameters are difficult to employ. + NOTE: selecting this option will disable the '__ro_after_init' + kernel hardening feature for security hooks. Please consider + using the selinux=0 boot parameter instead of enabling this + option. + If you are unsure how to answer this question, answer N. config SECURITY_SELINUX_DEVELOP -- 2.25.1
