path: root/mm/kasan/shadow.c

// 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/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 check_memory_region((unsigned long)p, size, false, _RET_IP_);
}
EXPORT_SYMBOL(__kasan_check_read);

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

#undef memset
void *memset(void *addr, int c, size_t len)
{
	if (!check_memory_region((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 (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
	    !check_memory_region((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 (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
	    !check_memory_region((unsigned long)dest, len, true, _RET_IP_))
		return NULL;

	return __memcpy(dest, src, len);
}

/*
 * Poisons the shadow memory for 'size' bytes starting from 'addr'.
 * Memory addresses should be aligned to KASAN_GRANULE_SIZE.
 */
void poison_range(const void *address, size_t size, u8 value)
{
	void *shadow_start, *shadow_end;

	/*
	 * 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.
	 */
	address = reset_tag(address);

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

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

void unpoison_range(const void *address, size_t size)
{
	u8 tag = get_tag(address);

	/*
	 * 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.
	 */
	address = reset_tag(address);

	poison_range(address, size, tag);

	if (size & KASAN_GRANULE_MASK) {
		u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);

		if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
			*shadow = tag;
		else
			*shadow = size & KASAN_GRANULE_MASK;
	}
}

#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_GRANULE_SIZE << PAGE_SHIFT)))
		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

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