mm/slab: remove HAVE_HARDENED_USERCOPY_ALLOCATOR

With SLOB removed, both remaining allocators support hardened usercopy,
so remove the config and associated #ifdef.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>

mm/Kconfig

@@ -221,7 +221,6 @@ choice
 config SLAB
 	bool "SLAB"
 	depends on !PREEMPT_RT
-	select HAVE_HARDENED_USERCOPY_ALLOCATOR
 	help
 	  The regular slab allocator that is established and known to work
 	  well in all environments. It organizes cache hot objects in
@@ -229,7 +228,6 @@ config SLAB
 
 config SLUB
 	bool "SLUB (Unqueued Allocator)"
-	select HAVE_HARDENED_USERCOPY_ALLOCATOR
 	help
 	   SLUB is a slab allocator that minimizes cache line usage
 	   instead of managing queues of cached objects (SLAB approach).

mm/slab.h

@@ -832,16 +832,8 @@ struct kmem_obj_info {
 void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab);
 #endif
 
-#ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR
 void __check_heap_object(const void *ptr, unsigned long n,
 			 const struct slab *slab, bool to_user);
-#else
-static inline
-void __check_heap_object(const void *ptr, unsigned long n,
-			 const struct slab *slab, bool to_user)
-{
-}
-#endif
 
 #ifdef CONFIG_SLUB_DEBUG
 void skip_orig_size_check(struct kmem_cache *s, const void *object);

security/Kconfig

@@ -127,16 +127,8 @@ config LSM_MMAP_MIN_ADDR
 	  this low address space will need the permission specific to the
 	  systems running LSM.
 
-config HAVE_HARDENED_USERCOPY_ALLOCATOR
-	bool
-	help
-	  The heap allocator implements __check_heap_object() for
-	  validating memory ranges against heap object sizes in
-	  support of CONFIG_HARDENED_USERCOPY.
-
 config HARDENED_USERCOPY
 	bool "Harden memory copies between kernel and userspace"
-	depends on HAVE_HARDENED_USERCOPY_ALLOCATOR
 	imply STRICT_DEVMEM
 	help
 	  This option checks for obviously wrong memory regions when