bpf: lsm: Initialize the BPF LSM hooks

* The hooks are initialized using the definitions in
  include/linux/lsm_hook_defs.h.
* The LSM can be enabled / disabled with CONFIG_BPF_LSM.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-6-kpsingh@chromium.org

security/Kconfig

@@ -277,11 +277,11 @@ endchoice
 
 config LSM
 	string "Ordered list of enabled LSMs"
-	default "lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor" if DEFAULT_SECURITY_SMACK
-	default "lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo" if DEFAULT_SECURITY_APPARMOR
-	default "lockdown,yama,loadpin,safesetid,integrity,tomoyo" if DEFAULT_SECURITY_TOMOYO
-	default "lockdown,yama,loadpin,safesetid,integrity" if DEFAULT_SECURITY_DAC
-	default "lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor"
+	default "lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK
+	default "lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR
+	default "lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO
+	default "lockdown,yama,loadpin,safesetid,integrity,bpf" if DEFAULT_SECURITY_DAC
+	default "lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf"
 	help
 	  A comma-separated list of LSMs, in initialization order.
 	  Any LSMs left off this list will be ignored. This can be

security/Makefile

@@ -12,6 +12,7 @@ subdir-$(CONFIG_SECURITY_YAMA)		+= yama
 subdir-$(CONFIG_SECURITY_LOADPIN)	+= loadpin
 subdir-$(CONFIG_SECURITY_SAFESETID)    += safesetid
 subdir-$(CONFIG_SECURITY_LOCKDOWN_LSM)	+= lockdown
+subdir-$(CONFIG_BPF_LSM)		+= bpf
 
 # always enable default capabilities
 obj-y					+= commoncap.o
@@ -30,6 +31,7 @@ obj-$(CONFIG_SECURITY_LOADPIN)		+= loadpin/
 obj-$(CONFIG_SECURITY_SAFESETID)       += safesetid/
 obj-$(CONFIG_SECURITY_LOCKDOWN_LSM)	+= lockdown/
 obj-$(CONFIG_CGROUP_DEVICE)		+= device_cgroup.o
+obj-$(CONFIG_BPF_LSM)			+= bpf/
 
 # Object integrity file lists
 subdir-$(CONFIG_INTEGRITY)		+= integrity

security/bpf/Makefile

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (C) 2020 Google LLC.
+
+obj-$(CONFIG_BPF_LSM) := hooks.o

security/bpf/hooks.c

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2020 Google LLC.
+ */
+#include <linux/lsm_hooks.h>
+#include <linux/bpf_lsm.h>
+
+static struct security_hook_list bpf_lsm_hooks[] __lsm_ro_after_init = {
+	#define LSM_HOOK(RET, DEFAULT, NAME, ...) \
+	LSM_HOOK_INIT(NAME, bpf_lsm_##NAME),
+	#include <linux/lsm_hook_defs.h>
+	#undef LSM_HOOK
+};
+
+static int __init bpf_lsm_init(void)
+{
+	security_add_hooks(bpf_lsm_hooks, ARRAY_SIZE(bpf_lsm_hooks), "bpf");
+	pr_info("LSM support for eBPF active\n");
+	return 0;
+}
+
+DEFINE_LSM(bpf) = {
+	.name = "bpf",
+	.init = bpf_lsm_init,
+};