+ kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: kasan: introduce ARCH_DEFER_KASAN and unify static key across modes
has been added to the -mm mm-unstable branch.  Its filename is
     kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Subject: kasan: introduce ARCH_DEFER_KASAN and unify static key across modes
Date: Sun, 10 Aug 2025 17:57:45 +0500

Patch series "kasan: unify kasan_enabled() and remove arch-specific
implementations", v6.

This patch series addresses the fragmentation in KASAN initialization
across architectures by introducing a unified approach that eliminates
duplicate static keys and arch-specific kasan_arch_is_ready()
implementations.

The core issue is that different architectures have inconsistent approaches
to KASAN readiness tracking:
- PowerPC, LoongArch, and UML arch, each implement own kasan_arch_is_ready()
- Only HW_TAGS mode had a unified static key (kasan_flag_enabled)
- Generic and SW_TAGS modes relied on arch-specific solutions
  or always-on behavior


This patch (of 2):

Introduce CONFIG_ARCH_DEFER_KASAN to identify architectures [1] that need
to defer KASAN initialization until shadow memory is properly set up, and
unify the static key infrastructure across all KASAN modes.

[1] PowerPC, UML, LoongArch selects ARCH_DEFER_KASAN.

The core issue is that different architectures haveinconsistent approaches
to KASAN readiness tracking:
- PowerPC, LoongArch, and UML arch, each implement own
  kasan_arch_is_ready()
- Only HW_TAGS mode had a unified static key (kasan_flag_enabled)
- Generic and SW_TAGS modes relied on arch-specific solutions or always-on
    behavior

This patch addresses the fragmentation in KASAN initialization across
architectures by introducing a unified approach that eliminates duplicate
static keys and arch-specific kasan_arch_is_ready() implementations.

Let's replace kasan_arch_is_ready() with existing kasan_enabled() check,
which examines the static key being enabled if arch selects
ARCH_DEFER_KASAN or has HW_TAGS mode support.  For other arch,
kasan_enabled() checks the enablement during compile time.

Now KASAN users can use a single kasan_enabled() check everywhere.

Link: https://lkml.kernel.org/r/20250810125746.1105476-1-snovitoll@gmail.com
Link: https://lkml.kernel.org/r/20250810125746.1105476-2-snovitoll@gmail.com
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217049
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: David Gow <davidgow@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Marco Elver <elver@google.com>
Cc: Qing Zhang <zhangqing@loongson.cn>
Cc: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/loongarch/Kconfig                 |    1 
 arch/loongarch/include/asm/kasan.h     |    7 -----
 arch/loongarch/mm/kasan_init.c         |    8 ++---
 arch/powerpc/Kconfig                   |    1 
 arch/powerpc/include/asm/kasan.h       |   12 --------
 arch/powerpc/mm/kasan/init_32.c        |    2 -
 arch/powerpc/mm/kasan/init_book3e_64.c |    2 -
 arch/powerpc/mm/kasan/init_book3s_64.c |    6 ----
 arch/um/Kconfig                        |    1 
 arch/um/include/asm/kasan.h            |    5 +--
 arch/um/kernel/mem.c                   |   13 +++++++--
 include/linux/kasan-enabled.h          |   32 ++++++++++++++++-------
 include/linux/kasan.h                  |    6 ++++
 lib/Kconfig.kasan                      |   12 ++++++++
 mm/kasan/common.c                      |   17 +++++++++---
 mm/kasan/generic.c                     |   19 ++++++++++---
 mm/kasan/hw_tags.c                     |    9 ------
 mm/kasan/kasan.h                       |    8 +++++
 mm/kasan/shadow.c                      |   12 ++++----
 mm/kasan/sw_tags.c                     |    1 
 mm/kasan/tags.c                        |    2 -
 21 files changed, 106 insertions(+), 70 deletions(-)

--- a/arch/loongarch/include/asm/kasan.h~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/arch/loongarch/include/asm/kasan.h
@@ -66,7 +66,6 @@
 #define XKPRANGE_WC_SHADOW_OFFSET	(KASAN_SHADOW_START + XKPRANGE_WC_KASAN_OFFSET)
 #define XKVRANGE_VC_SHADOW_OFFSET	(KASAN_SHADOW_START + XKVRANGE_VC_KASAN_OFFSET)
 
-extern bool kasan_early_stage;
 extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
 
 #define kasan_mem_to_shadow kasan_mem_to_shadow
@@ -75,12 +74,6 @@ void *kasan_mem_to_shadow(const void *ad
 #define kasan_shadow_to_mem kasan_shadow_to_mem
 const void *kasan_shadow_to_mem(const void *shadow_addr);
 
-#define kasan_arch_is_ready kasan_arch_is_ready
-static __always_inline bool kasan_arch_is_ready(void)
-{
-	return !kasan_early_stage;
-}
-
 #define addr_has_metadata addr_has_metadata
 static __always_inline bool addr_has_metadata(const void *addr)
 {
--- a/arch/loongarch/Kconfig~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/arch/loongarch/Kconfig
@@ -9,6 +9,7 @@ config LOONGARCH
 	select ACPI_PPTT if ACPI
 	select ACPI_SYSTEM_POWER_STATES_SUPPORT	if ACPI
 	select ARCH_BINFMT_ELF_STATE
+	select ARCH_NEEDS_DEFER_KASAN
 	select ARCH_DISABLE_KASAN_INLINE
 	select ARCH_ENABLE_MEMORY_HOTPLUG
 	select ARCH_ENABLE_MEMORY_HOTREMOVE
--- a/arch/loongarch/mm/kasan_init.c~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/arch/loongarch/mm/kasan_init.c
@@ -40,11 +40,9 @@ static pgd_t kasan_pg_dir[PTRS_PER_PGD]
 #define __pte_none(early, pte) (early ? pte_none(pte) : \
 ((pte_val(pte) & _PFN_MASK) == (unsigned long)__pa(kasan_early_shadow_page)))
 
-bool kasan_early_stage = true;
-
 void *kasan_mem_to_shadow(const void *addr)
 {
-	if (!kasan_arch_is_ready()) {
+	if (!kasan_enabled()) {
 		return (void *)(kasan_early_shadow_page);
 	} else {
 		unsigned long maddr = (unsigned long)addr;
@@ -298,7 +296,8 @@ void __init kasan_init(void)
 	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
 					kasan_mem_to_shadow((void *)KFENCE_AREA_END));
 
-	kasan_early_stage = false;
+	/* Enable KASAN here before kasan_mem_to_shadow(). */
+	kasan_init_generic();
 
 	/* Populate the linear mapping */
 	for_each_mem_range(i, &pa_start, &pa_end) {
@@ -329,5 +328,4 @@ void __init kasan_init(void)
 
 	/* At this point kasan is fully initialized. Enable error messages */
 	init_task.kasan_depth = 0;
-	pr_info("KernelAddressSanitizer initialized.\n");
 }
--- a/arch/powerpc/include/asm/kasan.h~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/arch/powerpc/include/asm/kasan.h
@@ -53,18 +53,6 @@
 #endif
 
 #ifdef CONFIG_KASAN
-#ifdef CONFIG_PPC_BOOK3S_64
-DECLARE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
-
-static __always_inline bool kasan_arch_is_ready(void)
-{
-	if (static_branch_likely(&powerpc_kasan_enabled_key))
-		return true;
-	return false;
-}
-
-#define kasan_arch_is_ready kasan_arch_is_ready
-#endif
 
 void kasan_early_init(void);
 void kasan_mmu_init(void);
--- a/arch/powerpc/Kconfig~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/arch/powerpc/Kconfig
@@ -122,6 +122,7 @@ config PPC
 	# Please keep this list sorted alphabetically.
 	#
 	select ARCH_32BIT_OFF_T if PPC32
+	select ARCH_NEEDS_DEFER_KASAN		if PPC_RADIX_MMU
 	select ARCH_DISABLE_KASAN_INLINE	if PPC_RADIX_MMU
 	select ARCH_DMA_DEFAULT_COHERENT	if !NOT_COHERENT_CACHE
 	select ARCH_ENABLE_MEMORY_HOTPLUG
--- a/arch/powerpc/mm/kasan/init_32.c~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/arch/powerpc/mm/kasan/init_32.c
@@ -165,7 +165,7 @@ void __init kasan_init(void)
 
 	/* At this point kasan is fully initialized. Enable error messages */
 	init_task.kasan_depth = 0;
-	pr_info("KASAN init done\n");
+	kasan_init_generic();
 }
 
 void __init kasan_late_init(void)
--- a/arch/powerpc/mm/kasan/init_book3e_64.c~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/arch/powerpc/mm/kasan/init_book3e_64.c
@@ -127,7 +127,7 @@ void __init kasan_init(void)
 
 	/* Enable error messages */
 	init_task.kasan_depth = 0;
-	pr_info("KASAN init done\n");
+	kasan_init_generic();
 }
 
 void __init kasan_late_init(void) { }
--- a/arch/powerpc/mm/kasan/init_book3s_64.c~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/arch/powerpc/mm/kasan/init_book3s_64.c
@@ -19,8 +19,6 @@
 #include <linux/memblock.h>
 #include <asm/pgalloc.h>
 
-DEFINE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
-
 static void __init kasan_init_phys_region(void *start, void *end)
 {
 	unsigned long k_start, k_end, k_cur;
@@ -92,11 +90,9 @@ void __init kasan_init(void)
 	 */
 	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
 
-	static_branch_inc(&powerpc_kasan_enabled_key);
-
 	/* Enable error messages */
 	init_task.kasan_depth = 0;
-	pr_info("KASAN init done\n");
+	kasan_init_generic();
 }
 
 void __init kasan_early_init(void) { }
--- a/arch/um/include/asm/kasan.h~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/arch/um/include/asm/kasan.h
@@ -24,10 +24,9 @@
 
 #ifdef CONFIG_KASAN
 void kasan_init(void);
-extern int kasan_um_is_ready;
 
-#ifdef CONFIG_STATIC_LINK
-#define kasan_arch_is_ready() (kasan_um_is_ready)
+#if defined(CONFIG_STATIC_LINK) && defined(CONFIG_KASAN_INLINE)
+#error UML does not work in KASAN_INLINE mode with STATIC_LINK enabled!
 #endif
 #else
 static inline void kasan_init(void) { }
--- a/arch/um/Kconfig~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/arch/um/Kconfig
@@ -5,6 +5,7 @@ menu "UML-specific options"
 config UML
 	bool
 	default y
+	select ARCH_NEEDS_DEFER_KASAN if STATIC_LINK
 	select ARCH_WANTS_DYNAMIC_TASK_STRUCT
 	select ARCH_HAS_CACHE_LINE_SIZE
 	select ARCH_HAS_CPU_FINALIZE_INIT
--- a/arch/um/kernel/mem.c~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/arch/um/kernel/mem.c
@@ -21,10 +21,10 @@
 #include <os.h>
 #include <um_malloc.h>
 #include <linux/sched/task.h>
+#include <linux/kasan.h>
 
 #ifdef CONFIG_KASAN
-int kasan_um_is_ready;
-void kasan_init(void)
+void __init kasan_init(void)
 {
 	/*
 	 * kasan_map_memory will map all of the required address space and
@@ -32,7 +32,11 @@ void kasan_init(void)
 	 */
 	kasan_map_memory((void *)KASAN_SHADOW_START, KASAN_SHADOW_SIZE);
 	init_task.kasan_depth = 0;
-	kasan_um_is_ready = true;
+	/*
+	 * Since kasan_init() is called before main(),
+	 * KASAN is initialized but the enablement is deferred after
+	 * jump_label_init(). See arch_mm_preinit().
+	 */
 }
 
 static void (*kasan_init_ptr)(void)
@@ -58,6 +62,9 @@ static unsigned long brk_end;
 
 void __init arch_mm_preinit(void)
 {
+	/* Safe to call after jump_label_init(). Enables KASAN. */
+	kasan_init_generic();
+
 	/* clear the zero-page */
 	memset(empty_zero_page, 0, PAGE_SIZE);
 
--- a/include/linux/kasan-enabled.h~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/include/linux/kasan-enabled.h
@@ -4,32 +4,46 @@
 
 #include <linux/static_key.h>
 
-#ifdef CONFIG_KASAN_HW_TAGS
-
+#if defined(CONFIG_ARCH_DEFER_KASAN) || defined(CONFIG_KASAN_HW_TAGS)
+/*
+ * Global runtime flag for KASAN modes that need runtime control.
+ * Used by ARCH_DEFER_KASAN architectures and HW_TAGS mode.
+ */
 DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
 
+/*
+ * Runtime control for shadow memory initialization or HW_TAGS mode.
+ * Uses static key for architectures that need deferred KASAN or HW_TAGS.
+ */
 static __always_inline bool kasan_enabled(void)
 {
 	return static_branch_likely(&kasan_flag_enabled);
 }
 
-static inline bool kasan_hw_tags_enabled(void)
+static inline void kasan_enable(void)
 {
-	return kasan_enabled();
+	static_branch_enable(&kasan_flag_enabled);
 }
-
-#else /* CONFIG_KASAN_HW_TAGS */
-
-static inline bool kasan_enabled(void)
+#else
+/* For architectures that can enable KASAN early, use compile-time check. */
+static __always_inline bool kasan_enabled(void)
 {
 	return IS_ENABLED(CONFIG_KASAN);
 }
 
+static inline void kasan_enable(void) {}
+#endif /* CONFIG_ARCH_DEFER_KASAN || CONFIG_KASAN_HW_TAGS */
+
+#ifdef CONFIG_KASAN_HW_TAGS
+static inline bool kasan_hw_tags_enabled(void)
+{
+	return kasan_enabled();
+}
+#else
 static inline bool kasan_hw_tags_enabled(void)
 {
 	return false;
 }
-
 #endif /* CONFIG_KASAN_HW_TAGS */
 
 #endif /* LINUX_KASAN_ENABLED_H */
--- a/include/linux/kasan.h~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/include/linux/kasan.h
@@ -543,6 +543,12 @@ void kasan_report_async(void);
 
 #endif /* CONFIG_KASAN_HW_TAGS */
 
+#ifdef CONFIG_KASAN_GENERIC
+void __init kasan_init_generic(void);
+#else
+static inline void kasan_init_generic(void) { }
+#endif
+
 #ifdef CONFIG_KASAN_SW_TAGS
 void __init kasan_init_sw_tags(void);
 #else
--- a/lib/Kconfig.kasan~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/lib/Kconfig.kasan
@@ -19,6 +19,18 @@ config ARCH_DISABLE_KASAN_INLINE
 	  Disables both inline and stack instrumentation. Selected by
 	  architectures that do not support these instrumentation types.
 
+config ARCH_NEEDS_DEFER_KASAN
+	bool
+
+config ARCH_DEFER_KASAN
+	def_bool y
+	depends on KASAN && ARCH_NEEDS_DEFER_KASAN
+	help
+	  Architectures should select this if they need to defer KASAN
+	  initialization until shadow memory is properly set up. This
+	  enables runtime control via static keys. Otherwise, KASAN uses
+	  compile-time constants for better performance.
+
 config CC_HAS_KASAN_GENERIC
 	def_bool $(cc-option, -fsanitize=kernel-address)
 
--- a/mm/kasan/common.c~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/mm/kasan/common.c
@@ -32,6 +32,15 @@
 #include "kasan.h"
 #include "../slab.h"
 
+#if defined(CONFIG_ARCH_DEFER_KASAN) || defined(CONFIG_KASAN_HW_TAGS)
+/*
+ * Definition of the unified static key declared in kasan-enabled.h.
+ * This provides consistent runtime enable/disable across KASAN modes.
+ */
+DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
+EXPORT_SYMBOL_GPL(kasan_flag_enabled);
+#endif
+
 struct slab *kasan_addr_to_slab(const void *addr)
 {
 	if (virt_addr_valid(addr))
@@ -246,7 +255,7 @@ static inline void poison_slab_object(st
 bool __kasan_slab_pre_free(struct kmem_cache *cache, void *object,
 				unsigned long ip)
 {
-	if (!kasan_arch_is_ready() || is_kfence_address(object))
+	if (is_kfence_address(object))
 		return false;
 	return check_slab_allocation(cache, object, ip);
 }
@@ -254,7 +263,7 @@ bool __kasan_slab_pre_free(struct kmem_c
 bool __kasan_slab_free(struct kmem_cache *cache, void *object, bool init,
 		       bool still_accessible)
 {
-	if (!kasan_arch_is_ready() || is_kfence_address(object))
+	if (is_kfence_address(object))
 		return false;
 
 	/*
@@ -293,7 +302,7 @@ bool __kasan_slab_free(struct kmem_cache
 
 static inline bool check_page_allocation(void *ptr, unsigned long ip)
 {
-	if (!kasan_arch_is_ready())
+	if (!kasan_enabled())
 		return false;
 
 	if (ptr != page_address(virt_to_head_page(ptr))) {
@@ -522,7 +531,7 @@ bool __kasan_mempool_poison_object(void
 		return true;
 	}
 
-	if (is_kfence_address(ptr) || !kasan_arch_is_ready())
+	if (is_kfence_address(ptr))
 		return true;
 
 	slab = folio_slab(folio);
--- a/mm/kasan/generic.c~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/mm/kasan/generic.c
@@ -37,6 +37,17 @@
 #include "../slab.h"
 
 /*
+ * Initialize Generic KASAN and enable runtime checks.
+ * This should be called from arch kasan_init() once shadow memory is ready.
+ */
+void __init kasan_init_generic(void)
+{
+	kasan_enable();
+
+	pr_info("KernelAddressSanitizer initialized (generic)\n");
+}
+
+/*
  * All functions below always inlined so compiler could
  * perform better optimizations in each of __asan_loadX/__assn_storeX
  * depending on memory access size X.
@@ -165,7 +176,7 @@ static __always_inline bool check_region
 						size_t size, bool write,
 						unsigned long ret_ip)
 {
-	if (!kasan_arch_is_ready())
+	if (!kasan_enabled())
 		return true;
 
 	if (unlikely(size == 0))
@@ -193,7 +204,7 @@ bool kasan_byte_accessible(const void *a
 {
 	s8 shadow_byte;
 
-	if (!kasan_arch_is_ready())
+	if (!kasan_enabled())
 		return true;
 
 	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));
@@ -495,7 +506,7 @@ static void release_alloc_meta(struct ka
 
 static void release_free_meta(const void *object, struct kasan_free_meta *meta)
 {
-	if (!kasan_arch_is_ready())
+	if (!kasan_enabled())
 		return;
 
 	/* Check if free meta is valid. */
@@ -562,7 +573,7 @@ void kasan_save_alloc_info(struct kmem_c
 	kasan_save_track(&alloc_meta->alloc_track, flags);
 }
 
-void kasan_save_free_info(struct kmem_cache *cache, void *object)
+void __kasan_save_free_info(struct kmem_cache *cache, void *object)
 {
 	struct kasan_free_meta *free_meta;
 
--- a/mm/kasan/hw_tags.c~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/mm/kasan/hw_tags.c
@@ -46,13 +46,6 @@ static enum kasan_arg_mode kasan_arg_mod
 static enum kasan_arg_vmalloc kasan_arg_vmalloc __initdata;
 
 /*
- * Whether KASAN is enabled at all.
- * The value remains false until KASAN is initialized by kasan_init_hw_tags().
- */
-DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
-EXPORT_SYMBOL(kasan_flag_enabled);
-
-/*
  * Whether the selected mode is synchronous, asynchronous, or asymmetric.
  * Defaults to KASAN_MODE_SYNC.
  */
@@ -260,7 +253,7 @@ void __init kasan_init_hw_tags(void)
 	kasan_init_tags();
 
 	/* KASAN is now initialized, enable it. */
-	static_branch_enable(&kasan_flag_enabled);
+	kasan_enable();
 
 	pr_info("KernelAddressSanitizer initialized (hw-tags, mode=%s, vmalloc=%s, stacktrace=%s)\n",
 		kasan_mode_info(),
--- a/mm/kasan/kasan.h~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/mm/kasan/kasan.h
@@ -398,7 +398,13 @@ depot_stack_handle_t kasan_save_stack(gf
 void kasan_set_track(struct kasan_track *track, depot_stack_handle_t stack);
 void kasan_save_track(struct kasan_track *track, gfp_t flags);
 void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags);
-void kasan_save_free_info(struct kmem_cache *cache, void *object);
+
+void __kasan_save_free_info(struct kmem_cache *cache, void *object);
+static inline void kasan_save_free_info(struct kmem_cache *cache, void *object)
+{
+	if (kasan_enabled())
+		__kasan_save_free_info(cache, object);
+}
 
 #ifdef CONFIG_KASAN_GENERIC
 bool kasan_quarantine_put(struct kmem_cache *cache, void *object);
--- a/mm/kasan/shadow.c~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/mm/kasan/shadow.c
@@ -125,7 +125,7 @@ void kasan_poison(const void *addr, size
 {
 	void *shadow_start, *shadow_end;
 
-	if (!kasan_arch_is_ready())
+	if (!kasan_enabled())
 		return;
 
 	/*
@@ -150,7 +150,7 @@ EXPORT_SYMBOL_GPL(kasan_poison);
 #ifdef CONFIG_KASAN_GENERIC
 void kasan_poison_last_granule(const void *addr, size_t size)
 {
-	if (!kasan_arch_is_ready())
+	if (!kasan_enabled())
 		return;
 
 	if (size & KASAN_GRANULE_MASK) {
@@ -390,7 +390,7 @@ int kasan_populate_vmalloc(unsigned long
 	unsigned long shadow_start, shadow_end;
 	int ret;
 
-	if (!kasan_arch_is_ready())
+	if (!kasan_enabled())
 		return 0;
 
 	if (!is_vmalloc_or_module_addr((void *)addr))
@@ -560,7 +560,7 @@ void kasan_release_vmalloc(unsigned long
 	unsigned long region_start, region_end;
 	unsigned long size;
 
-	if (!kasan_arch_is_ready())
+	if (!kasan_enabled())
 		return;
 
 	region_start = ALIGN(start, KASAN_MEMORY_PER_SHADOW_PAGE);
@@ -611,7 +611,7 @@ void *__kasan_unpoison_vmalloc(const voi
 	 * with setting memory tags, so the KASAN_VMALLOC_INIT flag is ignored.
 	 */
 
-	if (!kasan_arch_is_ready())
+	if (!kasan_enabled())
 		return (void *)start;
 
 	if (!is_vmalloc_or_module_addr(start))
@@ -636,7 +636,7 @@ void *__kasan_unpoison_vmalloc(const voi
  */
 void __kasan_poison_vmalloc(const void *start, unsigned long size)
 {
-	if (!kasan_arch_is_ready())
+	if (!kasan_enabled())
 		return;
 
 	if (!is_vmalloc_or_module_addr(start))
--- a/mm/kasan/sw_tags.c~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/mm/kasan/sw_tags.c
@@ -44,6 +44,7 @@ void __init kasan_init_sw_tags(void)
 		per_cpu(prng_state, cpu) = (u32)get_cycles();
 
 	kasan_init_tags();
+	kasan_enable();
 
 	pr_info("KernelAddressSanitizer initialized (sw-tags, stacktrace=%s)\n",
 		str_on_off(kasan_stack_collection_enabled()));
--- a/mm/kasan/tags.c~kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes
+++ a/mm/kasan/tags.c
@@ -142,7 +142,7 @@ void kasan_save_alloc_info(struct kmem_c
 	save_stack_info(cache, object, flags, false);
 }
 
-void kasan_save_free_info(struct kmem_cache *cache, void *object)
+void __kasan_save_free_info(struct kmem_cache *cache, void *object)
 {
 	save_stack_info(cache, object, 0, true);
 }
_

Patches currently in -mm which might be from snovitoll@gmail.com are

kasan-introduce-arch_defer_kasan-and-unify-static-key-across-modes.patch
kasan-call-kasan_init_generic-in-kasan_init.patch