livepatch: Cancel transition a safe way for immediate patches

klp_init_transition() does not set func->transition for immediate patches.
Then klp_ftrace_handler() could use the new code immediately. As a result,
it is not safe to put the livepatch module in klp_cancel_transition().

This patch reverts most of the last minute changes klp_cancel_transition().
It keeps the warning about a misuse because it still makes sense.

Fixes: 3ec24776 ("livepatch: allow removal of a disabled patch")
Signed-off-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

kernel/livepatch/transition.c

@@ -120,31 +120,11 @@ static void klp_complete_transition(void)
  */
 void klp_cancel_transition(void)
 {
-	struct klp_patch *patch = klp_transition_patch;
-	struct klp_object *obj;
-	struct klp_func *func;
-	bool immediate_func = false;
-
 	if (WARN_ON_ONCE(klp_target_state != KLP_PATCHED))
 		return;
 
 	klp_target_state = KLP_UNPATCHED;
 	klp_complete_transition();
-
-	/*
-	 * In the enable error path, even immediate patches can be safely
-	 * removed because the transition hasn't been started yet.
-	 *
-	 * klp_complete_transition() doesn't have a module_put() for immediate
-	 * patches, so do it here.
-	 */
-	klp_for_each_object(patch, obj)
-		klp_for_each_func(obj, func)
-			if (func->immediate)
-				immediate_func = true;
-
-	if (patch->immediate || immediate_func)
-		module_put(patch->mod);
 }
 
 /*