mm/kasan/report_sw_tags.c

// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains software tag-based KASAN specific error reporting code.
 *
 * 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/bitops.h>
#include <linux/ftrace.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/printk.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/stackdepot.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/kasan.h>
#include <linux/module.h>

#include <asm/sections.h>

#include "kasan.h"
#include "../slab.h"

const char *kasan_get_bug_type(struct kasan_access_info *info)
{
#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
	struct kasan_alloc_meta *alloc_meta;
	struct kmem_cache *cache;
	struct page *page;
	const void *addr;
	void *object;
	u8 tag;
	int i;

	tag = get_tag(info->access_addr);
	addr = kasan_reset_tag(info->access_addr);
	page = kasan_addr_to_page(addr);
	if (page && PageSlab(page)) {
		cache = page->slab_cache;
		object = nearest_obj(cache, page, (void *)addr);
		alloc_meta = kasan_get_alloc_meta(cache, object);

		if (alloc_meta) {
			for (i = 0; i < KASAN_NR_FREE_STACKS; i++) {
				if (alloc_meta->free_pointer_tag[i] == tag)
					return "use-after-free";
			}
		}
		return "out-of-bounds";
	}

#endif
	/*
	 * If access_size is a negative number, then it has reason to be
	 * defined as out-of-bounds bug type.
	 *
	 * Casting negative numbers to size_t would indeed turn up as
	 * a large size_t and its value will be larger than ULONG_MAX/2,
	 * so that this can qualify as out-of-bounds.
	 */
	if (info->access_addr + info->access_size < info->access_addr)
		return "out-of-bounds";

	return "invalid-access";
}

void *kasan_find_first_bad_addr(void *addr, size_t size)
{
	u8 tag = get_tag(addr);
	void *p = kasan_reset_tag(addr);
	void *end = p + size;

	while (p < end && tag == *(u8 *)kasan_mem_to_shadow(p))
		p += KASAN_GRANULE_SIZE;
	return p;
}

void kasan_metadata_fetch_row(char *buffer, void *row)
{
	memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
}

void kasan_print_tags(u8 addr_tag, const void *addr)
{
	u8 *shadow = (u8 *)kasan_mem_to_shadow(addr);

	pr_err("Pointer tag: [%02x], memory tag: [%02x]\n", addr_tag, *shadow);
}