security: Add a "locked down" LSM hook

Add a mechanism to allow LSMs to make a policy decision around whether
kernel functionality that would allow tampering with or examining the
runtime state of the kernel should be permitted.

Signed-off-by: Matthew Garrett <mjg59@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/security/security.c b/security/security.c
index ef4a0111c8b4..7fc373486d7a 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2389,3 +2389,9 @@ void security_bpf_prog_free(struct bpf_prog_aux *aux)
         call_void_hook(bpf_prog_free_security, aux);
 }
 #endif /* CONFIG_BPF_SYSCALL */
+
+int security_locked_down(enum lockdown_reason what)
+{
+        return call_int_hook(locked_down, 0, what);
+}
+EXPORT_SYMBOL(security_locked_down);