Generic KASAN only saves stack traces for small kmalloc allocations. We can also save alloc/free stack traces for large kmalloc allocations (the ones the fall back to page_alloc when the size > KMALLOC_MAX_CACHE_SIZE). To store their handles, we can use in-object redzones for large kmalloc allocations (when they are large enough). Also see https://bugzilla.kernel.org/show_bug.cgi?id=203967 wrt saving stack traces for page_alloc allocations. (For the tag-based modes, we should use the stack ring instead: https://bugzilla.kernel.org/show_bug.cgi?id=216842.)