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>

Author: tehcaster

mm/Kconfig

@@ -221,15 +221,13 @@ 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
 	  per cpu and per node queues.
 
 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