From: Gentoo CachyOS overlay
Subject: [PATCH] mm/slub: stub check_set_canary_bulk() without SLAB_CANARY

The hardened patch defines check_set_canary_bulk() only under
CONFIG_SLAB_CANARY, but calls it unconditionally. The LTS config keeps
SLAB_MERGE_DEFAULT=y, so SLAB_CANARY is off and mm/slub.c fails to build.
Add a no-op stub next to the existing set_canary()/check_canary() stubs.

--- a/mm/slub.c
+++ b/mm/slub.c
@@ -941,6 +941,7 @@
 #else
 #define set_canary(s, object, value)
 #define check_canary(s, object, value)
+#define check_set_canary_bulk(s, size, objects, check_value, set_value)
 #endif
 
 #ifdef CONFIG_SLUB_DEBUG