lib/stackdepot: check disabled flag when fetching

Do not try fetching a stack trace from the stack depot if the
stack_depot_disabled flag is enabled.

Link: https://lkml.kernel.org/r/c3bfa3b7ab00b2e48ab75a3fbb9c67555777cb08.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/stackdepot.c

@@ -483,7 +483,7 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
 	 */
 	kmsan_unpoison_memory(entries, sizeof(*entries));
 
-	if (!handle)
+	if (!handle || stack_depot_disabled)
 		return 0;
 
 	if (parts.pool_index > pool_index_cached) {