kernel/module.c: use generic module param operaters for sig_enforce

We're directly checking and modifying sig_enforce when needed instead
of using the generic helpers. This prevents us from generalizing this
helper so that others can use it. Use indirect helpers to allow us
to generalize this code a bit and to make it a bit more clear what
this is doing.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: cocci@systeme.lip6.fr
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

kernel/module.c

@@ -301,23 +301,25 @@ static bool sig_enforce = false;
 static int param_set_bool_enable_only(const char *val,
 				      const struct kernel_param *kp)
 {
-	int err;
-	bool test;
+	int err = 0;
+	bool new_value;
+	bool orig_value = *(bool *)kp->arg;
 	struct kernel_param dummy_kp = *kp;
 
-	dummy_kp.arg = &test;
+	dummy_kp.arg = &new_value;
 
 	err = param_set_bool(val, &dummy_kp);
 	if (err)
 		return err;
 
 	/* Don't let them unset it once it's set! */
-	if (!test && sig_enforce)
+	if (!new_value && orig_value)
 		return -EROFS;
 
-	if (test)
-		sig_enforce = true;
-	return 0;
+	if (new_value)
+		err = param_set_bool(val, kp);
+
+	return err;
 }
 
 static const struct kernel_param_ops param_ops_bool_enable_only = {