UBUNTU: SAUCE: x86/bugs: Make boot modes __ro_after_init

CVE-2018-3639 (x86)

There's no reason for these to be changed after boot.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>

arch/x86/kernel/cpu/bugs.c

@@ -129,7 +129,8 @@ static const char *spectre_v2_strings[] = {
 #undef pr_fmt
 #define pr_fmt(fmt)     "Spectre V2 : " fmt
 
-static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE;
+static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
+	SPECTRE_V2_NONE;
 
 void x86_spec_ctrl_set(u64 val)
 {
@@ -432,7 +433,7 @@ static void __init spectre_v2_select_mitigation(void)
 #undef pr_fmt
 #define pr_fmt(fmt)	"Speculative Store Bypass: " fmt
 
-static enum ssb_mitigation ssb_mode = SPEC_STORE_BYPASS_NONE;
+static enum ssb_mitigation ssb_mode __ro_after_init = SPEC_STORE_BYPASS_NONE;
 
 /* The kernel command line selection */
 enum ssb_mitigation_cmd {