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security: introduce CONFIG_SECURITY_WRITABLE_HOOKS

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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@oracle.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
James Morris 2017-02-15 00:17:24 +11:00 committed by James Morris
parent 84e6885e9e
commit dd0859dccb
3 changed files with 18 additions and 0 deletions
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7
include/linux/lsm_hooks.h
View File

@ -1920,6 +1920,13 @@ 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

5
security/Kconfig
View File

@ -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 SECURITYFS
bool "Enable the securityfs filesystem"
help

6
security/selinux/Kconfig
View File

@ -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