mm/kasan/shadow.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * This file contains KASAN runtime code that manages shadow memory for
  * generic and software tag-based KASAN modes.
  *
  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
  *
  * Some code borrowed from https://github.com/xairy/kasan-prototype by
  *        Andrey Konovalov <andreyknvl@gmail.com>
  */

 #include <linux/init.h>
 #include <linux/kasan.h>
 #include <linux/kernel.h>
 #include <linux/kfence.h>
 #include <linux/kmemleak.h>
 #include <linux/memory.h>
 #include <linux/mm.h>
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/vmalloc.h>

 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>

 #include "kasan.h"

 bool __kasan_check_read(const volatile void *p, unsigned int size)
 {
 	return kasan_check_range((unsigned long)p, size, false, _RET_IP_);
 }
 EXPORT_SYMBOL(__kasan_check_read);

 bool __kasan_check_write(const volatile void *p, unsigned int size)
 {
 	return kasan_check_range((unsigned long)p, size, true, _RET_IP_);
 }
 EXPORT_SYMBOL(__kasan_check_write);

 #undef memset
 void *memset(void *addr, int c, size_t len)
 {
 	if (!kasan_check_range((unsigned long)addr, len, true, _RET_IP_))
 		return NULL;

 	return __memset(addr, c, len);
 }

 #ifdef __HAVE_ARCH_MEMMOVE
 #undef memmove
 void *memmove(void *dest, const void *src, size_t len)
 {
 	if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) ||
 	    !kasan_check_range((unsigned long)dest, len, true, _RET_IP_))
 		return NULL;

 	return __memmove(dest, src, len);
 }
 #endif

 #undef memcpy
 void *memcpy(void *dest, const void *src, size_t len)
 {
 	if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) ||
 	    !kasan_check_range((unsigned long)dest, len, true, _RET_IP_))
 		return NULL;

 	return __memcpy(dest, src, len);
 }

 void kasan_poison(const void *addr, size_t size, u8 value, bool init)
 {
 	void *shadow_start, *shadow_end;

 	if (!kasan_arch_is_ready())
 		return;

 	/*
 	 * Perform shadow offset calculation based on untagged address, as
 	 * some of the callers (e.g. kasan_poison_object_data) pass tagged
 	 * addresses to this function.
 	 */
 	addr = kasan_reset_tag(addr);

 	/* Skip KFENCE memory if called explicitly outside of sl*b. */
 	if (is_kfence_address(addr))
 		return;

 	if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
 		return;
 	if (WARN_ON(size & KASAN_GRANULE_MASK))
 		return;

 	shadow_start = kasan_mem_to_shadow(addr);
 	shadow_end = kasan_mem_to_shadow(addr + size);

 	__memset(shadow_start, value, shadow_end - shadow_start);
 }
 EXPORT_SYMBOL(kasan_poison);

 #ifdef CONFIG_KASAN_GENERIC
 void kasan_poison_last_granule(const void *addr, size_t size)
 {
 	if (!kasan_arch_is_ready())
 		return;

 	if (size & KASAN_GRANULE_MASK) {
 		u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size);
 		*shadow = size & KASAN_GRANULE_MASK;
 	}
 }
 #endif

 void kasan_unpoison(const void *addr, size_t size, bool init)
 {
 	u8 tag = get_tag(addr);

 	/*
 	 * Perform shadow offset calculation based on untagged address, as
 	 * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
 	 * addresses to this function.
 	 */
 	addr = kasan_reset_tag(addr);

 	/*
 	 * Skip KFENCE memory if called explicitly outside of sl*b. Also note
 	 * that calls to ksize(), where size is not a multiple of machine-word
 	 * size, would otherwise poison the invalid portion of the word.
 	 */
 	if (is_kfence_address(addr))
 		return;

 	if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
 		return;

 	/* Unpoison all granules that cover the object. */
 	kasan_poison(addr, round_up(size, KASAN_GRANULE_SIZE), tag, false);

 	/* Partially poison the last granule for the generic mode. */
 	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
 		kasan_poison_last_granule(addr, size);
 }

 #ifdef CONFIG_MEMORY_HOTPLUG
 static bool shadow_mapped(unsigned long addr)
 {
 	pgd_t *pgd = pgd_offset_k(addr);
 	p4d_t *p4d;
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;

 	if (pgd_none(*pgd))
 		return false;
 	p4d = p4d_offset(pgd, addr);
 	if (p4d_none(*p4d))
 		return false;
 	pud = pud_offset(p4d, addr);
 	if (pud_none(*pud))
 		return false;

 	/*
 	 * We can't use pud_large() or pud_huge(), the first one is
 	 * arch-specific, the last one depends on HUGETLB_PAGE.  So let's abuse
 	 * pud_bad(), if pud is bad then it's bad because it's huge.
 	 */
 	if (pud_bad(*pud))
 		return true;
 	pmd = pmd_offset(pud, addr);
 	if (pmd_none(*pmd))
 		return false;

 	if (pmd_bad(*pmd))
 		return true;
 	pte = pte_offset_kernel(pmd, addr);
 	return !pte_none(*pte);
 }

 static int __meminit kasan_mem_notifier(struct notifier_block *nb,
 			unsigned long action, void *data)
 {
 	struct memory_notify *mem_data = data;
 	unsigned long nr_shadow_pages, start_kaddr, shadow_start;
 	unsigned long shadow_end, shadow_size;

 	nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
 	start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
 	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
 	shadow_size = nr_shadow_pages << PAGE_SHIFT;
 	shadow_end = shadow_start + shadow_size;

 	if (WARN_ON(mem_data->nr_pages % KASAN_GRANULE_SIZE) ||
 		WARN_ON(start_kaddr % KASAN_MEMORY_PER_SHADOW_PAGE))
 		return NOTIFY_BAD;

 	switch (action) {
 	case MEM_GOING_ONLINE: {
 		void *ret;

 		/*
 		 * If shadow is mapped already than it must have been mapped
 		 * during the boot. This could happen if we onlining previously
 		 * offlined memory.
 		 */
 		if (shadow_mapped(shadow_start))
 			return NOTIFY_OK;

 		ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
 					shadow_end, GFP_KERNEL,
 					PAGE_KERNEL, VM_NO_GUARD,
 					pfn_to_nid(mem_data->start_pfn),
 					__builtin_return_address(0));
 		if (!ret)
 			return NOTIFY_BAD;

 		kmemleak_ignore(ret);
 		return NOTIFY_OK;
 	}
 	case MEM_CANCEL_ONLINE:
 	case MEM_OFFLINE: {
 		struct vm_struct *vm;

 		/*
 		 * shadow_start was either mapped during boot by kasan_init()
 		 * or during memory online by __vmalloc_node_range().
 		 * In the latter case we can use vfree() to free shadow.
 		 * Non-NULL result of the find_vm_area() will tell us if
 		 * that was the second case.
 		 *
 		 * Currently it's not possible to free shadow mapped
 		 * during boot by kasan_init(). It's because the code
 		 * to do that hasn't been written yet. So we'll just
 		 * leak the memory.
 		 */
 		vm = find_vm_area((void *)shadow_start);
 		if (vm)
 			vfree((void *)shadow_start);
 	}
 	}

 	return NOTIFY_OK;
 }

 static int __init kasan_memhotplug_init(void)
 {
 	hotplug_memory_notifier(kasan_mem_notifier, 0);

 	return 0;
 }

 core_initcall(kasan_memhotplug_init);
 #endif

 #ifdef CONFIG_KASAN_VMALLOC

 void __init __weak kasan_populate_early_vm_area_shadow(void *start,
 						       unsigned long size)
 {
 }

 static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
 				      void *unused)
 {
 	unsigned long page;
 	pte_t pte;

 	if (likely(!pte_none(*ptep)))
 		return 0;

 	page = __get_free_page(GFP_KERNEL);
 	if (!page)
 		return -ENOMEM;

 	memset((void *)page, KASAN_VMALLOC_INVALID, PAGE_SIZE);
 	pte = pfn_pte(PFN_DOWN(__pa(page)), PAGE_KERNEL);

 	spin_lock(&init_mm.page_table_lock);
 	if (likely(pte_none(*ptep))) {
 		set_pte_at(&init_mm, addr, ptep, pte);
 		page = 0;
 	}
 	spin_unlock(&init_mm.page_table_lock);
 	if (page)
 		free_page(page);
 	return 0;
 }

 int kasan_populate_vmalloc(unsigned long addr, unsigned long size)
 {
 	unsigned long shadow_start, shadow_end;
 	int ret;

 	if (!is_vmalloc_or_module_addr((void *)addr))
 		return 0;

 	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr);
 	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
 	shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size);
 	shadow_end = ALIGN(shadow_end, PAGE_SIZE);

 	ret = apply_to_page_range(&init_mm, shadow_start,
 				  shadow_end - shadow_start,
 				  kasan_populate_vmalloc_pte, NULL);
 	if (ret)
 		return ret;

 	flush_cache_vmap(shadow_start, shadow_end);

 	/*
 	 * We need to be careful about inter-cpu effects here. Consider:
 	 *
 	 *   CPU#0				  CPU#1
 	 * WRITE_ONCE(p, vmalloc(100));		while (x = READ_ONCE(p)) ;
 	 *					p[99] = 1;
 	 *
 	 * With compiler instrumentation, that ends up looking like this:
 	 *
 	 *   CPU#0				  CPU#1
 	 * // vmalloc() allocates memory
 	 * // let a = area->addr
 	 * // we reach kasan_populate_vmalloc
 	 * // and call kasan_unpoison:
 	 * STORE shadow(a), unpoison_val
 	 * ...
 	 * STORE shadow(a+99), unpoison_val	x = LOAD p
 	 * // rest of vmalloc process		<data dependency>
 	 * STORE p, a				LOAD shadow(x+99)
 	 *
 	 * If there is no barrier between the end of unpoisoning the shadow
 	 * and the store of the result to p, the stores could be committed
 	 * in a different order by CPU#0, and CPU#1 could erroneously observe
 	 * poison in the shadow.
 	 *
 	 * We need some sort of barrier between the stores.
 	 *
 	 * In the vmalloc() case, this is provided by a smp_wmb() in
 	 * clear_vm_uninitialized_flag(). In the per-cpu allocator and in
 	 * get_vm_area() and friends, the caller gets shadow allocated but
 	 * doesn't have any pages mapped into the virtual address space that
 	 * has been reserved. Mapping those pages in will involve taking and
 	 * releasing a page-table lock, which will provide the barrier.
 	 */

 	return 0;
 }

 /*
  * Poison the shadow for a vmalloc region. Called as part of the
  * freeing process at the time the region is freed.
  */
 void kasan_poison_vmalloc(const void *start, unsigned long size)
 {
 	if (!is_vmalloc_or_module_addr(start))
 		return;

 	size = round_up(size, KASAN_GRANULE_SIZE);
 	kasan_poison(start, size, KASAN_VMALLOC_INVALID, false);
 }

 void kasan_unpoison_vmalloc(const void *start, unsigned long size)
 {
 	if (!is_vmalloc_or_module_addr(start))
 		return;

 	kasan_unpoison(start, size, false);
 }

 static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
 					void *unused)
 {
 	unsigned long page;

 	page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT);

 	spin_lock(&init_mm.page_table_lock);

 	if (likely(!pte_none(*ptep))) {
 		pte_clear(&init_mm, addr, ptep);
 		free_page(page);
 	}
 	spin_unlock(&init_mm.page_table_lock);

 	return 0;
 }

 /*
  * Release the backing for the vmalloc region [start, end), which
  * lies within the free region [free_region_start, free_region_end).
  *
  * This can be run lazily, long after the region was freed. It runs
  * under vmap_area_lock, so it's not safe to interact with the vmalloc/vmap
  * infrastructure.
  *
  * How does this work?
  * -------------------
  *
  * We have a region that is page aligned, labeled as A.
  * That might not map onto the shadow in a way that is page-aligned:
  *
  *                    start                     end
  *                    v                         v
  * |????????|????????|AAAAAAAA|AA....AA|AAAAAAAA|????????| < vmalloc
  *  -------- -------- --------          -------- --------
  *      |        |       |                 |        |
  *      |        |       |         /-------/        |
  *      \-------\|/------/         |/---------------/
  *              |||                ||
  *             |??AAAAAA|AAAAAAAA|AA??????|                < shadow
  *                 (1)      (2)      (3)
  *
  * First we align the start upwards and the end downwards, so that the
  * shadow of the region aligns with shadow page boundaries. In the
  * example, this gives us the shadow page (2). This is the shadow entirely
  * covered by this allocation.
  *
  * Then we have the tricky bits. We want to know if we can free the
  * partially covered shadow pages - (1) and (3) in the example. For this,
  * we are given the start and end of the free region that contains this
  * allocation. Extending our previous example, we could have:
  *
  *  free_region_start                                    free_region_end
  *  |                 start                     end      |
  *  v                 v                         v        v
  * |FFFFFFFF|FFFFFFFF|AAAAAAAA|AA....AA|AAAAAAAA|FFFFFFFF| < vmalloc
  *  -------- -------- --------          -------- --------
  *      |        |       |                 |        |
  *      |        |       |         /-------/        |
  *      \-------\|/------/         |/---------------/
  *              |||                ||
  *             |FFAAAAAA|AAAAAAAA|AAF?????|                < shadow
  *                 (1)      (2)      (3)
  *
  * Once again, we align the start of the free region up, and the end of
  * the free region down so that the shadow is page aligned. So we can free
  * page (1) - we know no allocation currently uses anything in that page,
  * because all of it is in the vmalloc free region. But we cannot free
  * page (3), because we can't be sure that the rest of it is unused.
  *
  * We only consider pages that contain part of the original region for
  * freeing: we don't try to free other pages from the free region or we'd
  * end up trying to free huge chunks of virtual address space.
  *
  * Concurrency
  * -----------
  *
  * How do we know that we're not freeing a page that is simultaneously
  * being used for a fresh allocation in kasan_populate_vmalloc(_pte)?
  *
  * We _can_ have kasan_release_vmalloc and kasan_populate_vmalloc running
  * at the same time. While we run under free_vmap_area_lock, the population
  * code does not.
  *
  * free_vmap_area_lock instead operates to ensure that the larger range
  * [free_region_start, free_region_end) is safe: because __alloc_vmap_area and
  * the per-cpu region-finding algorithm both run under free_vmap_area_lock,
  * no space identified as free will become used while we are running. This
  * means that so long as we are careful with alignment and only free shadow
  * pages entirely covered by the free region, we will not run in to any
  * trouble - any simultaneous allocations will be for disjoint regions.
  */
 void kasan_release_vmalloc(unsigned long start, unsigned long end,
 			   unsigned long free_region_start,
 			   unsigned long free_region_end)
 {
 	void *shadow_start, *shadow_end;
 	unsigned long region_start, region_end;
 	unsigned long size;

 	region_start = ALIGN(start, KASAN_MEMORY_PER_SHADOW_PAGE);
 	region_end = ALIGN_DOWN(end, KASAN_MEMORY_PER_SHADOW_PAGE);

 	free_region_start = ALIGN(free_region_start, KASAN_MEMORY_PER_SHADOW_PAGE);

 	if (start != region_start &&
 	    free_region_start < region_start)
 		region_start -= KASAN_MEMORY_PER_SHADOW_PAGE;

 	free_region_end = ALIGN_DOWN(free_region_end, KASAN_MEMORY_PER_SHADOW_PAGE);

 	if (end != region_end &&
 	    free_region_end > region_end)
 		region_end += KASAN_MEMORY_PER_SHADOW_PAGE;

 	shadow_start = kasan_mem_to_shadow((void *)region_start);
 	shadow_end = kasan_mem_to_shadow((void *)region_end);

 	if (shadow_end > shadow_start) {
 		size = shadow_end - shadow_start;
 		apply_to_existing_page_range(&init_mm,
 					     (unsigned long)shadow_start,
 					     size, kasan_depopulate_vmalloc_pte,
 					     NULL);
 		flush_tlb_kernel_range((unsigned long)shadow_start,
 				       (unsigned long)shadow_end);
 	}
 }

 #else /* CONFIG_KASAN_VMALLOC */

 int kasan_module_alloc(void *addr, size_t size)
 {
 	void *ret;
 	size_t scaled_size;
 	size_t shadow_size;
 	unsigned long shadow_start;

 	shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
 	scaled_size = (size + KASAN_GRANULE_SIZE - 1) >>
 				KASAN_SHADOW_SCALE_SHIFT;
 	shadow_size = round_up(scaled_size, PAGE_SIZE);

 	if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
 		return -EINVAL;

 	ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 			shadow_start + shadow_size,
 			GFP_KERNEL,
 			PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 			__builtin_return_address(0));

 	if (ret) {
 		__memset(ret, KASAN_SHADOW_INIT, shadow_size);
 		find_vm_area(addr)->flags |= VM_KASAN;
 		kmemleak_ignore(ret);
 		return 0;
 	}

 	return -ENOMEM;
 }

 void kasan_free_shadow(const struct vm_struct *vm)
 {
 	if (vm->flags & VM_KASAN)
 		vfree(kasan_mem_to_shadow(vm->addr));
 }

 #endif
	// SPDX-License-Identifier: GPL-2.0
	/*
	* This file contains KASAN runtime code that manages shadow memory for
	* generic and software tag-based KASAN modes.
	*
	* Copyright (c) 2014 Samsung Electronics Co., Ltd.
	* Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
	*
	* Some code borrowed from https://github.com/xairy/kasan-prototype by
	* Andrey Konovalov <andreyknvl@gmail.com>
	*/

	#include <linux/init.h>
	#include <linux/kasan.h>
	#include <linux/kernel.h>
	#include <linux/kfence.h>
	#include <linux/kmemleak.h>
	#include <linux/memory.h>
	#include <linux/mm.h>
	#include <linux/string.h>
	#include <linux/types.h>
	#include <linux/vmalloc.h>

	#include <asm/cacheflush.h>
	#include <asm/tlbflush.h>

	#include "kasan.h"

	bool __kasan_check_read(const volatile void *p, unsigned int size)
	{
	return kasan_check_range((unsigned long)p, size, false, _RET_IP_);
	}
	EXPORT_SYMBOL(__kasan_check_read);

	bool __kasan_check_write(const volatile void *p, unsigned int size)
	{
	return kasan_check_range((unsigned long)p, size, true, _RET_IP_);
	}
	EXPORT_SYMBOL(__kasan_check_write);

	#undef memset
	void memset(void addr, int c, size_t len)
	{
	if (!kasan_check_range((unsigned long)addr, len, true, _RET_IP_))
	return NULL;

	return __memset(addr, c, len);
	}

	#ifdef __HAVE_ARCH_MEMMOVE
	#undef memmove
	void memmove(void dest, const void *src, size_t len)
	{
	if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) \|\|
	!kasan_check_range((unsigned long)dest, len, true, _RET_IP_))
	return NULL;

	return __memmove(dest, src, len);
	}
	#endif

	#undef memcpy
	void memcpy(void dest, const void *src, size_t len)
	{
	if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) \|\|
	!kasan_check_range((unsigned long)dest, len, true, _RET_IP_))
	return NULL;

	return __memcpy(dest, src, len);
	}

	void kasan_poison(const void *addr, size_t size, u8 value, bool init)
	{
	void shadow_start, shadow_end;

	if (!kasan_arch_is_ready())
	return;

	/*
	* Perform shadow offset calculation based on untagged address, as
	* some of the callers (e.g. kasan_poison_object_data) pass tagged
	* addresses to this function.
	*/
	addr = kasan_reset_tag(addr);

	/* Skip KFENCE memory if called explicitly outside of slb. /
	if (is_kfence_address(addr))
	return;

	if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
	return;
	if (WARN_ON(size & KASAN_GRANULE_MASK))
	return;

	shadow_start = kasan_mem_to_shadow(addr);
	shadow_end = kasan_mem_to_shadow(addr + size);

	__memset(shadow_start, value, shadow_end - shadow_start);
	}
	EXPORT_SYMBOL(kasan_poison);

	#ifdef CONFIG_KASAN_GENERIC
	void kasan_poison_last_granule(const void *addr, size_t size)
	{
	if (!kasan_arch_is_ready())
	return;

	if (size & KASAN_GRANULE_MASK) {
	u8 shadow = (u8 )kasan_mem_to_shadow(addr + size);
	*shadow = size & KASAN_GRANULE_MASK;
	}
	}
	#endif

	void kasan_unpoison(const void *addr, size_t size, bool init)
	{
	u8 tag = get_tag(addr);

	/*
	* Perform shadow offset calculation based on untagged address, as
	* some of the callers (e.g. kasan_unpoison_object_data) pass tagged
	* addresses to this function.
	*/
	addr = kasan_reset_tag(addr);

	/*
	* Skip KFENCE memory if called explicitly outside of sl*b. Also note
	* that calls to ksize(), where size is not a multiple of machine-word
	* size, would otherwise poison the invalid portion of the word.
	*/
	if (is_kfence_address(addr))
	return;

	if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
	return;

	/* Unpoison all granules that cover the object. */
	kasan_poison(addr, round_up(size, KASAN_GRANULE_SIZE), tag, false);

	/* Partially poison the last granule for the generic mode. */
	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
	kasan_poison_last_granule(addr, size);
	}

	#ifdef CONFIG_MEMORY_HOTPLUG
	static bool shadow_mapped(unsigned long addr)
	{
	pgd_t *pgd = pgd_offset_k(addr);
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	if (pgd_none(*pgd))
	return false;
	p4d = p4d_offset(pgd, addr);
	if (p4d_none(*p4d))
	return false;
	pud = pud_offset(p4d, addr);
	if (pud_none(*pud))
	return false;

	/*
	* We can't use pud_large() or pud_huge(), the first one is
	* arch-specific, the last one depends on HUGETLB_PAGE. So let's abuse
	* pud_bad(), if pud is bad then it's bad because it's huge.
	*/
	if (pud_bad(*pud))
	return true;
	pmd = pmd_offset(pud, addr);
	if (pmd_none(*pmd))
	return false;

	if (pmd_bad(*pmd))
	return true;
	pte = pte_offset_kernel(pmd, addr);
	return !pte_none(*pte);
	}

	static int __meminit kasan_mem_notifier(struct notifier_block *nb,
	unsigned long action, void *data)
	{
	struct memory_notify *mem_data = data;
	unsigned long nr_shadow_pages, start_kaddr, shadow_start;
	unsigned long shadow_end, shadow_size;

	nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
	start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
	shadow_size = nr_shadow_pages << PAGE_SHIFT;
	shadow_end = shadow_start + shadow_size;

	if (WARN_ON(mem_data->nr_pages % KASAN_GRANULE_SIZE) \|\|
	WARN_ON(start_kaddr % KASAN_MEMORY_PER_SHADOW_PAGE))
	return NOTIFY_BAD;

	switch (action) {
	case MEM_GOING_ONLINE: {
	void *ret;

	/*
	* If shadow is mapped already than it must have been mapped
	* during the boot. This could happen if we onlining previously
	* offlined memory.
	*/
	if (shadow_mapped(shadow_start))
	return NOTIFY_OK;

	ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
	shadow_end, GFP_KERNEL,
	PAGE_KERNEL, VM_NO_GUARD,
	pfn_to_nid(mem_data->start_pfn),
	__builtin_return_address(0));
	if (!ret)
	return NOTIFY_BAD;

	kmemleak_ignore(ret);
	return NOTIFY_OK;
	}
	case MEM_CANCEL_ONLINE:
	case MEM_OFFLINE: {
	struct vm_struct *vm;

	/*
	* shadow_start was either mapped during boot by kasan_init()
	* or during memory online by __vmalloc_node_range().
	* In the latter case we can use vfree() to free shadow.
	* Non-NULL result of the find_vm_area() will tell us if
	* that was the second case.
	*
	* Currently it's not possible to free shadow mapped
	* during boot by kasan_init(). It's because the code
	* to do that hasn't been written yet. So we'll just
	* leak the memory.
	*/
	vm = find_vm_area((void *)shadow_start);
	if (vm)
	vfree((void *)shadow_start);
	}
	}

	return NOTIFY_OK;
	}

	static int __init kasan_memhotplug_init(void)
	{
	hotplug_memory_notifier(kasan_mem_notifier, 0);

	return 0;
	}

	core_initcall(kasan_memhotplug_init);
	#endif

	#ifdef CONFIG_KASAN_VMALLOC

	void __init __weak kasan_populate_early_vm_area_shadow(void *start,
	unsigned long size)
	{
	}

	static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
	void *unused)
	{
	unsigned long page;
	pte_t pte;

	if (likely(!pte_none(*ptep)))
	return 0;

	page = __get_free_page(GFP_KERNEL);
	if (!page)
	return -ENOMEM;

	memset((void *)page, KASAN_VMALLOC_INVALID, PAGE_SIZE);
	pte = pfn_pte(PFN_DOWN(__pa(page)), PAGE_KERNEL);

	spin_lock(&init_mm.page_table_lock);
	if (likely(pte_none(*ptep))) {
	set_pte_at(&init_mm, addr, ptep, pte);
	page = 0;
	}
	spin_unlock(&init_mm.page_table_lock);
	if (page)
	free_page(page);
	return 0;
	}

	int kasan_populate_vmalloc(unsigned long addr, unsigned long size)
	{
	unsigned long shadow_start, shadow_end;
	int ret;

	if (!is_vmalloc_or_module_addr((void *)addr))
	return 0;

	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr);
	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
	shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size);
	shadow_end = ALIGN(shadow_end, PAGE_SIZE);

	ret = apply_to_page_range(&init_mm, shadow_start,
	shadow_end - shadow_start,
	kasan_populate_vmalloc_pte, NULL);
	if (ret)
	return ret;

	flush_cache_vmap(shadow_start, shadow_end);

	/*
	* We need to be careful about inter-cpu effects here. Consider:
	*
	* CPU#0 CPU#1
	* WRITE_ONCE(p, vmalloc(100)); while (x = READ_ONCE(p)) ;
	* p[99] = 1;
	*
	* With compiler instrumentation, that ends up looking like this:
	*
	* CPU#0 CPU#1
	* // vmalloc() allocates memory
	* // let a = area->addr
	* // we reach kasan_populate_vmalloc
	* // and call kasan_unpoison:
	* STORE shadow(a), unpoison_val
	* ...
	* STORE shadow(a+99), unpoison_val x = LOAD p
	* // rest of vmalloc process <data dependency>
	* STORE p, a LOAD shadow(x+99)
	*
	* If there is no barrier between the end of unpoisoning the shadow
	* and the store of the result to p, the stores could be committed
	* in a different order by CPU#0, and CPU#1 could erroneously observe
	* poison in the shadow.
	*
	* We need some sort of barrier between the stores.
	*
	* In the vmalloc() case, this is provided by a smp_wmb() in
	* clear_vm_uninitialized_flag(). In the per-cpu allocator and in
	* get_vm_area() and friends, the caller gets shadow allocated but
	* doesn't have any pages mapped into the virtual address space that
	* has been reserved. Mapping those pages in will involve taking and
	* releasing a page-table lock, which will provide the barrier.
	*/

	return 0;
	}

	/*
	* Poison the shadow for a vmalloc region. Called as part of the
	* freeing process at the time the region is freed.
	*/
	void kasan_poison_vmalloc(const void *start, unsigned long size)
	{
	if (!is_vmalloc_or_module_addr(start))
	return;

	size = round_up(size, KASAN_GRANULE_SIZE);
	kasan_poison(start, size, KASAN_VMALLOC_INVALID, false);
	}

	void kasan_unpoison_vmalloc(const void *start, unsigned long size)
	{
	if (!is_vmalloc_or_module_addr(start))
	return;

	kasan_unpoison(start, size, false);
	}

	static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
	void *unused)
	{
	unsigned long page;

	page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT);

	spin_lock(&init_mm.page_table_lock);

	if (likely(!pte_none(*ptep))) {
	pte_clear(&init_mm, addr, ptep);
	free_page(page);
	}
	spin_unlock(&init_mm.page_table_lock);

	return 0;
	}

	/*
	* Release the backing for the vmalloc region [start, end), which
	* lies within the free region [free_region_start, free_region_end).
	*
	* This can be run lazily, long after the region was freed. It runs
	* under vmap_area_lock, so it's not safe to interact with the vmalloc/vmap
	* infrastructure.
	*
	* How does this work?
	* -------------------
	*
	* We have a region that is page aligned, labeled as A.
	* That might not map onto the shadow in a way that is page-aligned:
	*
	* start end
	* v v
	* \|????????\|????????\|AAAAAAAA\|AA....AA\|AAAAAAAA\|????????\| < vmalloc
	* -------- -------- -------- -------- --------
	* \| \| \| \| \|
	* \| \| \| /-------/ \|
	* \-------\\|/------/ \|/---------------/
	* \|\|\| \|\|
	* \|??AAAAAA\|AAAAAAAA\|AA??????\| < shadow
	* (1) (2) (3)
	*
	* First we align the start upwards and the end downwards, so that the
	* shadow of the region aligns with shadow page boundaries. In the
	* example, this gives us the shadow page (2). This is the shadow entirely
	* covered by this allocation.
	*
	* Then we have the tricky bits. We want to know if we can free the
	* partially covered shadow pages - (1) and (3) in the example. For this,
	* we are given the start and end of the free region that contains this
	* allocation. Extending our previous example, we could have:
	*
	* free_region_start free_region_end
	* \| start end \|
	* v v v v
	* \|FFFFFFFF\|FFFFFFFF\|AAAAAAAA\|AA....AA\|AAAAAAAA\|FFFFFFFF\| < vmalloc
	* -------- -------- -------- -------- --------
	* \| \| \| \| \|
	* \| \| \| /-------/ \|
	* \-------\\|/------/ \|/---------------/
	* \|\|\| \|\|
	* \|FFAAAAAA\|AAAAAAAA\|AAF?????\| < shadow
	* (1) (2) (3)
	*
	* Once again, we align the start of the free region up, and the end of
	* the free region down so that the shadow is page aligned. So we can free
	* page (1) - we know no allocation currently uses anything in that page,
	* because all of it is in the vmalloc free region. But we cannot free
	* page (3), because we can't be sure that the rest of it is unused.
	*
	* We only consider pages that contain part of the original region for
	* freeing: we don't try to free other pages from the free region or we'd
	* end up trying to free huge chunks of virtual address space.
	*
	* Concurrency
	* -----------
	*
	* How do we know that we're not freeing a page that is simultaneously
	* being used for a fresh allocation in kasan_populate_vmalloc(_pte)?
	*
	* We _can_ have kasan_release_vmalloc and kasan_populate_vmalloc running
	* at the same time. While we run under free_vmap_area_lock, the population
	* code does not.
	*
	* free_vmap_area_lock instead operates to ensure that the larger range
	* [free_region_start, free_region_end) is safe: because __alloc_vmap_area and
	* the per-cpu region-finding algorithm both run under free_vmap_area_lock,
	* no space identified as free will become used while we are running. This
	* means that so long as we are careful with alignment and only free shadow
	* pages entirely covered by the free region, we will not run in to any
	* trouble - any simultaneous allocations will be for disjoint regions.
	*/
	void kasan_release_vmalloc(unsigned long start, unsigned long end,
	unsigned long free_region_start,
	unsigned long free_region_end)
	{
	void shadow_start, shadow_end;
	unsigned long region_start, region_end;
	unsigned long size;

	region_start = ALIGN(start, KASAN_MEMORY_PER_SHADOW_PAGE);
	region_end = ALIGN_DOWN(end, KASAN_MEMORY_PER_SHADOW_PAGE);

	free_region_start = ALIGN(free_region_start, KASAN_MEMORY_PER_SHADOW_PAGE);

	if (start != region_start &&
	free_region_start < region_start)
	region_start -= KASAN_MEMORY_PER_SHADOW_PAGE;

	free_region_end = ALIGN_DOWN(free_region_end, KASAN_MEMORY_PER_SHADOW_PAGE);

	if (end != region_end &&
	free_region_end > region_end)
	region_end += KASAN_MEMORY_PER_SHADOW_PAGE;

	shadow_start = kasan_mem_to_shadow((void *)region_start);
	shadow_end = kasan_mem_to_shadow((void *)region_end);

	if (shadow_end > shadow_start) {
	size = shadow_end - shadow_start;
	apply_to_existing_page_range(&init_mm,
	(unsigned long)shadow_start,
	size, kasan_depopulate_vmalloc_pte,
	NULL);
	flush_tlb_kernel_range((unsigned long)shadow_start,
	(unsigned long)shadow_end);
	}
	}

	#else /* CONFIG_KASAN_VMALLOC */

	int kasan_module_alloc(void *addr, size_t size)
	{
	void *ret;
	size_t scaled_size;
	size_t shadow_size;
	unsigned long shadow_start;

	shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
	scaled_size = (size + KASAN_GRANULE_SIZE - 1) >>
	KASAN_SHADOW_SCALE_SHIFT;
	shadow_size = round_up(scaled_size, PAGE_SIZE);

	if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
	return -EINVAL;

	ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
	shadow_start + shadow_size,
	GFP_KERNEL,
	PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
	__builtin_return_address(0));

	if (ret) {
	__memset(ret, KASAN_SHADOW_INIT, shadow_size);
	find_vm_area(addr)->flags \|= VM_KASAN;
	kmemleak_ignore(ret);
	return 0;
	}

	return -ENOMEM;
	}

	void kasan_free_shadow(const struct vm_struct *vm)
	{
	if (vm->flags & VM_KASAN)
	vfree(kasan_mem_to_shadow(vm->addr));
	}

	#endif