kasan: restructure kasan_report

Restructure kasan_report() to make reviewing the subsequent patches
easier.

Link: https://lkml.kernel.org/r/ca28042889858b8cc4724d3d4378387f90d7a59d.1646237226.git.andreyknvl@google.comSigned-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/kasan/report.c

@@ -457,15 +457,18 @@ static void __kasan_report(void *addr, size_t size, bool is_write,
 bool kasan_report(unsigned long addr, size_t size, bool is_write,
 			unsigned long ip)
 {
-	unsigned long flags = user_access_save();
-	bool ret = false;
+	unsigned long ua_flags = user_access_save();
+	bool ret = true;
 
-	if (likely(report_enabled())) {
-		__kasan_report((void *)addr, size, is_write, ip);
-		ret = true;
+	if (unlikely(!report_enabled())) {
+		ret = false;
+		goto out;
 	}
 
-	user_access_restore(flags);
+	__kasan_report((void *)addr, size, is_write, ip);
+
+out:
+	user_access_restore(ua_flags);
 
 	return ret;
 }