Merge branch 'slab/for-6.11/buckets' into slab/for-next

Merge all the slab patches previously collected on top of v6.10-rc1,
over cleanups/fixes that had to be based on rc6.

Documentation/core-api/memory-allocation.rst

@@ -145,7 +145,9 @@ smaller than page size.
 
 The address of a chunk allocated with `kmalloc` is aligned to at least
 ARCH_KMALLOC_MINALIGN bytes. For sizes which are a power of two, the
-alignment is also guaranteed to be at least the respective size.
+alignment is also guaranteed to be at least the respective size. For other
+sizes, the alignment is guaranteed to be at least the largest power-of-two
+divisor of the size.
 
 Chunks allocated with kmalloc() can be resized with krealloc(). Similarly
 to kmalloc_array(): a helper for resizing arrays is provided in the form of

include/linux/mm.h

@@ -1110,7 +1110,7 @@ static inline unsigned int compound_order(struct page *page)
  *
  * Return: The order of the folio.
  */
-static inline unsigned int folio_order(struct folio *folio)
+static inline unsigned int folio_order(const struct folio *folio)
 {
 	if (!folio_test_large(folio))
 		return 0;
@@ -2150,7 +2150,7 @@ static inline struct folio *folio_next(struct folio *folio)
  * it from being split.  It is not necessary for the folio to be locked.
  * Return: The base-2 logarithm of the size of this folio.
  */
-static inline unsigned int folio_shift(struct folio *folio)
+static inline unsigned int folio_shift(const struct folio *folio)
 {
 	return PAGE_SHIFT + folio_order(folio);
 }
@@ -2163,7 +2163,7 @@ static inline unsigned int folio_shift(struct folio *folio)
  * it from being split.  It is not necessary for the folio to be locked.
  * Return: The number of bytes in this folio.
  */
-static inline size_t folio_size(struct folio *folio)
+static inline size_t folio_size(const struct folio *folio)
 {
 	return PAGE_SIZE << folio_order(folio);
 }

include/linux/poison.h

@@ -38,11 +38,8 @@
  * Magic nums for obj red zoning.
  * Placed in the first word before and the first word after an obj.
  */
-#define	RED_INACTIVE	0x09F911029D74E35BULL	/* when obj is inactive */
-#define	RED_ACTIVE	0xD84156C5635688C0ULL	/* when obj is active */
-
-#define SLUB_RED_INACTIVE	0xbb
-#define SLUB_RED_ACTIVE		0xcc
+#define SLUB_RED_INACTIVE	0xbb	/* when obj is inactive */
+#define SLUB_RED_ACTIVE		0xcc	/* when obj is active */
 
 /* ...and for poisoning */
 #define	POISON_INUSE	0x5a	/* for use-uninitialised poisoning */

include/linux/slab.h

@@ -426,8 +426,9 @@ enum kmalloc_cache_type {
 	NR_KMALLOC_TYPES
 };
 
-extern struct kmem_cache *
-kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1];
+typedef struct kmem_cache * kmem_buckets[KMALLOC_SHIFT_HIGH + 1];
+
+extern kmem_buckets kmalloc_caches[NR_KMALLOC_TYPES];
 
 /*
  * Define gfp bits that should not be set for KMALLOC_NORMAL.
@@ -528,9 +529,6 @@ static_assert(PAGE_SHIFT <= 20);
 
 #include <linux/alloc_tag.h>
 
-void *__kmalloc_noprof(size_t size, gfp_t flags) __assume_kmalloc_alignment __alloc_size(1);
-#define __kmalloc(...)				alloc_hooks(__kmalloc_noprof(__VA_ARGS__))
-
 /**
  * kmem_cache_alloc - Allocate an object
  * @cachep: The cache to allocate from.
@@ -551,6 +549,10 @@ void *kmem_cache_alloc_lru_noprof(struct kmem_cache *s, struct list_lru *lru,
 
 void kmem_cache_free(struct kmem_cache *s, void *objp);
 
+kmem_buckets *kmem_buckets_create(const char *name, slab_flags_t flags,
+				  unsigned int useroffset, unsigned int usersize,
+				  void (*ctor)(void *));
+
 /*
  * Bulk allocation and freeing operations. These are accelerated in an
  * allocator specific way to avoid taking locks repeatedly or building
@@ -568,31 +570,49 @@ static __always_inline void kfree_bulk(size_t size, void **p)
 	kmem_cache_free_bulk(NULL, size, p);
 }
 
-void *__kmalloc_node_noprof(size_t size, gfp_t flags, int node) __assume_kmalloc_alignment
-							 __alloc_size(1);
-#define __kmalloc_node(...)			alloc_hooks(__kmalloc_node_noprof(__VA_ARGS__))
-
 void *kmem_cache_alloc_node_noprof(struct kmem_cache *s, gfp_t flags,
 				   int node) __assume_slab_alignment __malloc;
 #define kmem_cache_alloc_node(...)	alloc_hooks(kmem_cache_alloc_node_noprof(__VA_ARGS__))
 
-void *kmalloc_trace_noprof(struct kmem_cache *s, gfp_t flags, size_t size)
-		    __assume_kmalloc_alignment __alloc_size(3);
+/*
+ * These macros allow declaring a kmem_buckets * parameter alongside size, which
+ * can be compiled out with CONFIG_SLAB_BUCKETS=n so that a large number of call
+ * sites don't have to pass NULL.
+ */
+#ifdef CONFIG_SLAB_BUCKETS
+#define DECL_BUCKET_PARAMS(_size, _b)	size_t (_size), kmem_buckets *(_b)
+#define PASS_BUCKET_PARAMS(_size, _b)	(_size), (_b)
+#define PASS_BUCKET_PARAM(_b)		(_b)
+#else
+#define DECL_BUCKET_PARAMS(_size, _b)	size_t (_size)
+#define PASS_BUCKET_PARAMS(_size, _b)	(_size)
+#define PASS_BUCKET_PARAM(_b)		NULL
+#endif
 
-void *kmalloc_node_trace_noprof(struct kmem_cache *s, gfp_t gfpflags,
-		int node, size_t size) __assume_kmalloc_alignment
-						__alloc_size(4);
-#define kmalloc_trace(...)			alloc_hooks(kmalloc_trace_noprof(__VA_ARGS__))
+/*
+ * The following functions are not to be used directly and are intended only
+ * for internal use from kmalloc() and kmalloc_node()
+ * with the exception of kunit tests
+ */
 
-#define kmalloc_node_trace(...)			alloc_hooks(kmalloc_node_trace_noprof(__VA_ARGS__))
+void *__kmalloc_noprof(size_t size, gfp_t flags)
+				__assume_kmalloc_alignment __alloc_size(1);
 
-void *kmalloc_large_noprof(size_t size, gfp_t flags) __assume_page_alignment
-					      __alloc_size(1);
-#define kmalloc_large(...)			alloc_hooks(kmalloc_large_noprof(__VA_ARGS__))
+void *__kmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), gfp_t flags, int node)
+				__assume_kmalloc_alignment __alloc_size(1);
+
+void *__kmalloc_cache_noprof(struct kmem_cache *s, gfp_t flags, size_t size)
+				__assume_kmalloc_alignment __alloc_size(3);
 
-void *kmalloc_large_node_noprof(size_t size, gfp_t flags, int node) __assume_page_alignment
-							     __alloc_size(1);
-#define kmalloc_large_node(...)			alloc_hooks(kmalloc_large_node_noprof(__VA_ARGS__))
+void *__kmalloc_cache_node_noprof(struct kmem_cache *s, gfp_t gfpflags,
+				  int node, size_t size)
+				__assume_kmalloc_alignment __alloc_size(4);
+
+void *__kmalloc_large_noprof(size_t size, gfp_t flags)
+				__assume_page_alignment __alloc_size(1);
+
+void *__kmalloc_large_node_noprof(size_t size, gfp_t flags, int node)
+				__assume_page_alignment __alloc_size(1);
 
 /**
  * kmalloc - allocate kernel memory
@@ -604,7 +624,8 @@ void *kmalloc_large_node_noprof(size_t size, gfp_t flags, int node) __assume_pag
  *
  * The allocated object address is aligned to at least ARCH_KMALLOC_MINALIGN
  * bytes. For @size of power of two bytes, the alignment is also guaranteed
- * to be at least to the size.
+ * to be at least to the size. For other sizes, the alignment is guaranteed to
+ * be at least the largest power-of-two divisor of @size.
  *
  * The @flags argument may be one of the GFP flags defined at
  * include/linux/gfp_types.h and described at
@@ -654,10 +675,10 @@ static __always_inline __alloc_size(1) void *kmalloc_noprof(size_t size, gfp_t f
 		unsigned int index;
 
 		if (size > KMALLOC_MAX_CACHE_SIZE)
-			return kmalloc_large_noprof(size, flags);
+			return __kmalloc_large_noprof(size, flags);
 
 		index = kmalloc_index(size);
-		return kmalloc_trace_noprof(
+		return __kmalloc_cache_noprof(
 				kmalloc_caches[kmalloc_type(flags, _RET_IP_)][index],
 				flags, size);
 	}
@@ -665,20 +686,26 @@ static __always_inline __alloc_size(1) void *kmalloc_noprof(size_t size, gfp_t f
 }
 #define kmalloc(...)				alloc_hooks(kmalloc_noprof(__VA_ARGS__))
 
+#define kmem_buckets_alloc(_b, _size, _flags)	\
+	alloc_hooks(__kmalloc_node_noprof(PASS_BUCKET_PARAMS(_size, _b), _flags, NUMA_NO_NODE))
+
+#define kmem_buckets_alloc_track_caller(_b, _size, _flags)	\
+	alloc_hooks(__kmalloc_node_track_caller_noprof(PASS_BUCKET_PARAMS(_size, _b), _flags, NUMA_NO_NODE, _RET_IP_))
+
 static __always_inline __alloc_size(1) void *kmalloc_node_noprof(size_t size, gfp_t flags, int node)
 {
 	if (__builtin_constant_p(size) && size) {
 		unsigned int index;
 
 		if (size > KMALLOC_MAX_CACHE_SIZE)
-			return kmalloc_large_node_noprof(size, flags, node);
+			return __kmalloc_large_node_noprof(size, flags, node);
 
 		index = kmalloc_index(size);
-		return kmalloc_node_trace_noprof(
+		return __kmalloc_cache_node_noprof(
 				kmalloc_caches[kmalloc_type(flags, _RET_IP_)][index],
 				flags, node, size);
 	}
-	return __kmalloc_node_noprof(size, flags, node);
+	return __kmalloc_node_noprof(PASS_BUCKET_PARAMS(size, NULL), flags, node);
 }
 #define kmalloc_node(...)			alloc_hooks(kmalloc_node_noprof(__VA_ARGS__))
 
@@ -729,8 +756,10 @@ static inline __realloc_size(2, 3) void * __must_check krealloc_array_noprof(voi
  */
 #define kcalloc(n, size, flags)		kmalloc_array(n, size, (flags) | __GFP_ZERO)
 
-void *kmalloc_node_track_caller_noprof(size_t size, gfp_t flags, int node,
+void *__kmalloc_node_track_caller_noprof(DECL_BUCKET_PARAMS(size, b), gfp_t flags, int node,
 					 unsigned long caller) __alloc_size(1);
+#define kmalloc_node_track_caller_noprof(size, flags, node, caller) \
+	__kmalloc_node_track_caller_noprof(PASS_BUCKET_PARAMS(size, NULL), flags, node, caller)
 #define kmalloc_node_track_caller(...)		\
 	alloc_hooks(kmalloc_node_track_caller_noprof(__VA_ARGS__, _RET_IP_))
 
@@ -756,7 +785,7 @@ static inline __alloc_size(1, 2) void *kmalloc_array_node_noprof(size_t n, size_
 		return NULL;
 	if (__builtin_constant_p(n) && __builtin_constant_p(size))
 		return kmalloc_node_noprof(bytes, flags, node);
-	return __kmalloc_node_noprof(bytes, flags, node);
+	return __kmalloc_node_noprof(PASS_BUCKET_PARAMS(bytes, NULL), flags, node);
 }
 #define kmalloc_array_node(...)			alloc_hooks(kmalloc_array_node_noprof(__VA_ARGS__))
 
@@ -780,7 +809,9 @@ static inline __alloc_size(1) void *kzalloc_noprof(size_t size, gfp_t flags)
 #define kzalloc(...)				alloc_hooks(kzalloc_noprof(__VA_ARGS__))
 #define kzalloc_node(_size, _flags, _node)	kmalloc_node(_size, (_flags)|__GFP_ZERO, _node)
 
-extern void *kvmalloc_node_noprof(size_t size, gfp_t flags, int node) __alloc_size(1);
+void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), gfp_t flags, int node) __alloc_size(1);
+#define kvmalloc_node_noprof(size, flags, node)	\
+	__kvmalloc_node_noprof(PASS_BUCKET_PARAMS(size, NULL), flags, node)
 #define kvmalloc_node(...)			alloc_hooks(kvmalloc_node_noprof(__VA_ARGS__))
 
 #define kvmalloc(_size, _flags)			kvmalloc_node(_size, _flags, NUMA_NO_NODE)
@@ -788,6 +819,8 @@ extern void *kvmalloc_node_noprof(size_t size, gfp_t flags, int node) __alloc_si
 #define kvzalloc(_size, _flags)			kvmalloc(_size, (_flags)|__GFP_ZERO)
 
 #define kvzalloc_node(_size, _flags, _node)	kvmalloc_node(_size, (_flags)|__GFP_ZERO, _node)
+#define kmem_buckets_valloc(_b, _size, _flags)	\
+	alloc_hooks(__kvmalloc_node_noprof(PASS_BUCKET_PARAMS(_size, _b), _flags, NUMA_NO_NODE))
 
 static inline __alloc_size(1, 2) void *
 kvmalloc_array_node_noprof(size_t n, size_t size, gfp_t flags, int node)

ipc/msgutil.c

@@ -42,6 +42,17 @@ struct msg_msgseg {
 #define DATALEN_MSG	((size_t)PAGE_SIZE-sizeof(struct msg_msg))
 #define DATALEN_SEG	((size_t)PAGE_SIZE-sizeof(struct msg_msgseg))
 
+static kmem_buckets *msg_buckets __ro_after_init;
+
+static int __init init_msg_buckets(void)
+{
+	msg_buckets = kmem_buckets_create("msg_msg", SLAB_ACCOUNT,
+					  sizeof(struct msg_msg),
+					  DATALEN_MSG, NULL);
+
+	return 0;
+}
+subsys_initcall(init_msg_buckets);
 
 static struct msg_msg *alloc_msg(size_t len)
 {
@@ -50,7 +61,7 @@ static struct msg_msg *alloc_msg(size_t len)
 	size_t alen;
 
 	alen = min(len, DATALEN_MSG);
-	msg = kmalloc(sizeof(*msg) + alen, GFP_KERNEL_ACCOUNT);
+	msg = kmem_buckets_alloc(msg_buckets, sizeof(*msg) + alen, GFP_KERNEL);
 	if (msg == NULL)
 		return NULL;
 

kernel/configs/hardening.config

@@ -20,6 +20,7 @@ CONFIG_RANDOMIZE_MEMORY=y
 # Randomize allocator freelists, harden metadata.
 CONFIG_SLAB_FREELIST_RANDOM=y
 CONFIG_SLAB_FREELIST_HARDENED=y
+CONFIG_SLAB_BUCKETS=y
 CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
 CONFIG_RANDOM_KMALLOC_CACHES=y
 

lib/fortify_kunit.c

@@ -233,8 +233,6 @@ static void fortify_test_alloc_size_##allocator##_dynamic(struct kunit *test) \
 		kfree(p));						\
 	checker(expected_size,						\
 		kmalloc_array_node(alloc_size, 1, gfp, NUMA_NO_NODE),	\
-		kfree(p));						\
-	checker(expected_size, __kmalloc(alloc_size, gfp),		\
 		kfree(p));						\
 									\
 	orig = kmalloc(alloc_size, gfp);				\

lib/slub_kunit.c

@@ -140,7 +140,7 @@ static void test_kmalloc_redzone_access(struct kunit *test)
 {
 	struct kmem_cache *s = test_kmem_cache_create("TestSlub_RZ_kmalloc", 32,
 				SLAB_KMALLOC|SLAB_STORE_USER|SLAB_RED_ZONE);
-	u8 *p = kmalloc_trace(s, GFP_KERNEL, 18);
+	u8 *p = __kmalloc_cache_noprof(s, GFP_KERNEL, 18);
 
 	kasan_disable_current();
 

mm/Kconfig

@@ -273,6 +273,23 @@ config SLAB_FREELIST_HARDENED
 	  sacrifices to harden the kernel slab allocator against common
 	  freelist exploit methods.
 
+config SLAB_BUCKETS
+	bool "Support allocation from separate kmalloc buckets"
+	depends on !SLUB_TINY
+	default SLAB_FREELIST_HARDENED
+	help
+	  Kernel heap attacks frequently depend on being able to create
+	  specifically-sized allocations with user-controlled contents
+	  that will be allocated into the same kmalloc bucket as a
+	  target object. To avoid sharing these allocation buckets,
+	  provide an explicitly separated set of buckets to be used for
+	  user-controlled allocations. This may very slightly increase
+	  memory fragmentation, though in practice it's only a handful
+	  of extra pages since the bulk of user-controlled allocations
+	  are relatively long-lived.
+
+	  If unsure, say Y.
+
 config SLUB_STATS
 	default n
 	bool "Enable performance statistics"

mm/slab.h

@@ -168,7 +168,7 @@ static_assert(IS_ALIGNED(offsetof(struct slab, freelist), sizeof(freelist_aba_t)
  */
 static inline bool slab_test_pfmemalloc(const struct slab *slab)
 {
-	return folio_test_active((struct folio *)slab_folio(slab));
+	return folio_test_active(slab_folio(slab));
 }
 
 static inline void slab_set_pfmemalloc(struct slab *slab)
@@ -213,7 +213,7 @@ static inline struct slab *virt_to_slab(const void *addr)
 
 static inline int slab_order(const struct slab *slab)
 {
-	return folio_order((struct folio *)slab_folio(slab));
+	return folio_order(slab_folio(slab));
 }
 
 static inline size_t slab_size(const struct slab *slab)
@@ -405,16 +405,18 @@ static inline unsigned int size_index_elem(unsigned int bytes)
  * KMALLOC_MAX_CACHE_SIZE and the caller must check that.
  */
 static inline struct kmem_cache *
-kmalloc_slab(size_t size, gfp_t flags, unsigned long caller)
+kmalloc_slab(size_t size, kmem_buckets *b, gfp_t flags, unsigned long caller)
 {
 	unsigned int index;
 
+	if (!b)
+		b = &kmalloc_caches[kmalloc_type(flags, caller)];
 	if (size <= 192)
 		index = kmalloc_size_index[size_index_elem(size)];
 	else
 		index = fls(size - 1);
 
-	return kmalloc_caches[kmalloc_type(flags, caller)][index];
+	return (*b)[index];
 }
 
 gfp_t kmalloc_fix_flags(gfp_t flags);

mm/slab_common.c

@@ -392,6 +392,98 @@ kmem_cache_create(const char *name, unsigned int size, unsigned int align,
 }
 EXPORT_SYMBOL(kmem_cache_create);
 
+static struct kmem_cache *kmem_buckets_cache __ro_after_init;
+
+/**
+ * kmem_buckets_create - Create a set of caches that handle dynamic sized
+ *			 allocations via kmem_buckets_alloc()
+ * @name: A prefix string which is used in /proc/slabinfo to identify this
+ *	  cache. The individual caches with have their sizes as the suffix.
+ * @flags: SLAB flags (see kmem_cache_create() for details).
+ * @useroffset: Starting offset within an allocation that may be copied
+ *		to/from userspace.
+ * @usersize: How many bytes, starting at @useroffset, may be copied
+ *		to/from userspace.
+ * @ctor: A constructor for the objects, run when new allocations are made.
+ *
+ * Cannot be called within an interrupt, but can be interrupted.
+ *
+ * Return: a pointer to the cache on success, NULL on failure. When
+ * CONFIG_SLAB_BUCKETS is not enabled, ZERO_SIZE_PTR is returned, and
+ * subsequent calls to kmem_buckets_alloc() will fall back to kmalloc().
+ * (i.e. callers only need to check for NULL on failure.)
+ */
+kmem_buckets *kmem_buckets_create(const char *name, slab_flags_t flags,
+				  unsigned int useroffset,
+				  unsigned int usersize,
+				  void (*ctor)(void *))
+{
+	kmem_buckets *b;
+	int idx;
+
+	/*
+	 * When the separate buckets API is not built in, just return
+	 * a non-NULL value for the kmem_buckets pointer, which will be
+	 * unused when performing allocations.
+	 */
+	if (!IS_ENABLED(CONFIG_SLAB_BUCKETS))
+		return ZERO_SIZE_PTR;
+
+	if (WARN_ON(!kmem_buckets_cache))
+		return NULL;
+
+	b = kmem_cache_alloc(kmem_buckets_cache, GFP_KERNEL|__GFP_ZERO);
+	if (WARN_ON(!b))
+		return NULL;
+
+	flags |= SLAB_NO_MERGE;
+
+	for (idx = 0; idx < ARRAY_SIZE(kmalloc_caches[KMALLOC_NORMAL]); idx++) {
+		char *short_size, *cache_name;
+		unsigned int cache_useroffset, cache_usersize;
+		unsigned int size;
+
+		if (!kmalloc_caches[KMALLOC_NORMAL][idx])
+			continue;
+
+		size = kmalloc_caches[KMALLOC_NORMAL][idx]->object_size;
+		if (!size)
+			continue;
+
+		short_size = strchr(kmalloc_caches[KMALLOC_NORMAL][idx]->name, '-');
+		if (WARN_ON(!short_size))
+			goto fail;
+
+		cache_name = kasprintf(GFP_KERNEL, "%s-%s", name, short_size + 1);
+		if (WARN_ON(!cache_name))
+			goto fail;
+
+		if (useroffset >= size) {
+			cache_useroffset = 0;
+			cache_usersize = 0;
+		} else {
+			cache_useroffset = useroffset;
+			cache_usersize = min(size - cache_useroffset, usersize);
+		}
+		(*b)[idx] = kmem_cache_create_usercopy(cache_name, size,
+					0, flags, cache_useroffset,
+					cache_usersize, ctor);
+		kfree(cache_name);
+		if (WARN_ON(!(*b)[idx]))
+			goto fail;
+	}
+
+	return b;
+
+fail:
+	for (idx = 0; idx < ARRAY_SIZE(kmalloc_caches[KMALLOC_NORMAL]); idx++)
+		kmem_cache_destroy((*b)[idx]);
+	kfree(b);
+
+	return NULL;
+}
+EXPORT_SYMBOL(kmem_buckets_create);
+
 #ifdef SLAB_SUPPORTS_SYSFS
 /*
  * For a given kmem_cache, kmem_cache_destroy() should only be called
@@ -617,11 +709,12 @@ void __init create_boot_cache(struct kmem_cache *s, const char *name,
 	s->size = s->object_size = size;
 
 	/*
-	 * For power of two sizes, guarantee natural alignment for kmalloc
-	 * caches, regardless of SL*B debugging options.
+	 * kmalloc caches guarantee alignment of at least the largest
+	 * power-of-two divisor of the size. For power-of-two sizes,
+	 * it is the size itself.
 	 */
-	if (is_power_of_2(size))
-		align = max(align, size);
+	if (flags & SLAB_KMALLOC)
+		align = max(align, 1U << (ffs(size) - 1));
 	s->align = calculate_alignment(flags, align, size);
 
 #ifdef CONFIG_HARDENED_USERCOPY
@@ -653,8 +746,7 @@ static struct kmem_cache *__init create_kmalloc_cache(const char *name,
 	return s;
 }
 
-struct kmem_cache *
-kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1] __ro_after_init =
+kmem_buckets kmalloc_caches[NR_KMALLOC_TYPES] __ro_after_init =
 { /* initialization for https://llvm.org/pr42570 */ };
 EXPORT_SYMBOL(kmalloc_caches);
 
@@ -703,7 +795,7 @@ size_t kmalloc_size_roundup(size_t size)
 		 * The flags don't matter since size_index is common to all.
 		 * Neither does the caller for just getting ->object_size.
 		 */
-		return kmalloc_slab(size, GFP_KERNEL, 0)->object_size;
+		return kmalloc_slab(size, NULL, GFP_KERNEL, 0)->object_size;
 	}
 
 	/* Above the smaller buckets, size is a multiple of page size. */
@@ -932,6 +1024,11 @@ void __init create_kmalloc_caches(void)
 
 	/* Kmalloc array is now usable */
 	slab_state = UP;
+
+	if (IS_ENABLED(CONFIG_SLAB_BUCKETS))
+		kmem_buckets_cache = kmem_cache_create("kmalloc_buckets",
+						       sizeof(kmem_buckets),
+						       0, SLAB_NO_MERGE, NULL);
 }
 
 /**

mm/util.c

@@ -198,6 +198,16 @@ char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
 }
 EXPORT_SYMBOL(kmemdup_nul);
 
+static kmem_buckets *user_buckets __ro_after_init;
+
+static int __init init_user_buckets(void)
+{
+	user_buckets = kmem_buckets_create("memdup_user", 0, 0, INT_MAX, NULL);
+
+	return 0;
+}
+subsys_initcall(init_user_buckets);
+
 /**
  * memdup_user - duplicate memory region from user space
  *
@@ -211,7 +221,7 @@ void *memdup_user(const void __user *src, size_t len)
 {
 	void *p;
 
-	p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
+	p = kmem_buckets_alloc_track_caller(user_buckets, len, GFP_USER | __GFP_NOWARN);
 	if (!p)
 		return ERR_PTR(-ENOMEM);
 
@@ -237,7 +247,7 @@ void *vmemdup_user(const void __user *src, size_t len)
 {
 	void *p;
 
-	p = kvmalloc(len, GFP_USER);
+	p = kmem_buckets_valloc(user_buckets, len, GFP_USER);
 	if (!p)
 		return ERR_PTR(-ENOMEM);
 
@@ -594,9 +604,10 @@ unsigned long vm_mmap(struct file *file, unsigned long addr,
 EXPORT_SYMBOL(vm_mmap);
 
 /**
- * kvmalloc_node - attempt to allocate physically contiguous memory, but upon
+ * __kvmalloc_node - attempt to allocate physically contiguous memory, but upon
  * failure, fall back to non-contiguous (vmalloc) allocation.
  * @size: size of the request.
+ * @b: which set of kmalloc buckets to allocate from.
  * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL.
  * @node: numa node to allocate from
  *
@@ -609,7 +620,7 @@ EXPORT_SYMBOL(vm_mmap);
  *
  * Return: pointer to the allocated memory of %NULL in case of failure
  */
-void *kvmalloc_node_noprof(size_t size, gfp_t flags, int node)
+void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), gfp_t flags, int node)
 {
 	gfp_t kmalloc_flags = flags;
 	void *ret;
@@ -631,7 +642,7 @@ void *kvmalloc_node_noprof(size_t size, gfp_t flags, int node)
 		kmalloc_flags &= ~__GFP_NOFAIL;
 	}
 
-	ret = kmalloc_node_noprof(size, kmalloc_flags, node);
+	ret = __kmalloc_node_noprof(PASS_BUCKET_PARAMS(size, b), kmalloc_flags, node);
 
 	/*
 	 * It doesn't really make sense to fallback to vmalloc for sub page
@@ -660,7 +671,7 @@ void *kvmalloc_node_noprof(size_t size, gfp_t flags, int node)
 			flags, PAGE_KERNEL, VM_ALLOW_HUGE_VMAP,
 			node, __builtin_return_address(0));
 }
-EXPORT_SYMBOL(kvmalloc_node_noprof);
+EXPORT_SYMBOL(__kvmalloc_node_noprof);
 
 /**
  * kvfree() - Free memory.

rust/kernel/alloc/allocator.rs

@@ -18,23 +18,16 @@ pub(crate) unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: F
     // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first.
     let layout = new_layout.pad_to_align();
 
-    let mut size = layout.size();
-
-    if layout.align() > bindings::ARCH_SLAB_MINALIGN {
-        // The alignment requirement exceeds the slab guarantee, thus try to enlarge the size
-        // to use the "power-of-two" size/alignment guarantee (see comments in `kmalloc()` for
-        // more information).
-        //
-        // Note that `layout.size()` (after padding) is guaranteed to be a multiple of
-        // `layout.align()`, so `next_power_of_two` gives enough alignment guarantee.
-        size = size.next_power_of_two();
-    }
+    // Note that `layout.size()` (after padding) is guaranteed to be a multiple of `layout.align()`
+    // which together with the slab guarantees means the `krealloc` will return a properly aligned
+    // object (see comments in `kmalloc()` for more information).
+    let size = layout.size();
 
     // SAFETY:
     // - `ptr` is either null or a pointer returned from a previous `k{re}alloc()` by the
     //   function safety requirement.
-    // - `size` is greater than 0 since it's either a `layout.size()` (which cannot be zero
-    //   according to the function safety requirement) or a result from `next_power_of_two()`.
+    // - `size` is greater than 0 since it's from `layout.size()` (which cannot be zero according
+    //   to the function safety requirement)
     unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags.0) as *mut u8 }
 }
 

scripts/kernel-doc

@@ -1729,6 +1729,7 @@ sub dump_function($$) {
     $prototype =~ s/__printf\s*\(\s*\d*\s*,\s*\d*\s*\) +//;
     $prototype =~ s/__(?:re)?alloc_size\s*\(\s*\d+\s*(?:,\s*\d+\s*)?\) +//;
     $prototype =~ s/__diagnose_as\s*\(\s*\S+\s*(?:,\s*\d+\s*)*\) +//;
+    $prototype =~ s/DECL_BUCKET_PARAMS\s*\(\s*(\S+)\s*,\s*(\S+)\s*\)/$1, $2/;
     my $define = $prototype =~ s/^#\s*define\s+//; #ak added
     $prototype =~ s/__attribute_const__ +//;
     $prototype =~ s/__attribute__\s*\(\(

tools/include/linux/poison.h

@@ -47,11 +47,8 @@
  * Magic nums for obj red zoning.
  * Placed in the first word before and the first word after an obj.
  */
-#define	RED_INACTIVE	0x09F911029D74E35BULL	/* when obj is inactive */
-#define	RED_ACTIVE	0xD84156C5635688C0ULL	/* when obj is active */
-
-#define SLUB_RED_INACTIVE	0xbb
-#define SLUB_RED_ACTIVE		0xcc
+#define SLUB_RED_INACTIVE	0xbb	/* when obj is inactive */
+#define SLUB_RED_ACTIVE		0xcc	/* when obj is active */
 
 /* ...and for poisoning */
 #define	POISON_INUSE	0x5a	/* for use-uninitialised poisoning */