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// SPDX-License-Identifier: GPL-2.0
/*
* This file contains common generic and tag-based KASAN 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>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <common.h>
#include <linux/bitops.h>
#include <linux/kernel.h>
#include <printk.h>
#include <asm-generic/sections.h>
#include "kasan.h"
/* Shadow layout customization. */
#define SHADOW_BYTES_PER_BLOCK 1
#define SHADOW_BLOCKS_PER_ROW 16
#define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
#define SHADOW_ROWS_AROUND_ADDR 2
static unsigned long kasan_flags;
#define KASAN_BIT_REPORTED 0
#define KASAN_BIT_MULTI_SHOT 1
bool kasan_save_enable_multi_shot(void)
{
return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
}
EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
void kasan_restore_multi_shot(bool enabled)
{
if (!enabled)
clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
}
EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
static void print_error_description(struct kasan_access_info *info)
{
pr_err("BUG: KASAN: %s in %pS\n",
get_bug_type(info), (void *)info->ip);
pr_err("%s of size %zu at addr %px\n",
info->is_write ? "Write" : "Read", info->access_size,
info->access_addr);
}
static void start_report(unsigned long *flags)
{
/*
* Make sure we don't end up in loop.
*/
kasan_disable_current();
pr_err("==================================================================\n");
}
static void end_report(unsigned long *flags)
{
pr_err("==================================================================\n");
kasan_enable_current();
}
static inline bool kernel_or_module_addr(const void *addr)
{
if (addr >= (void *)_stext && addr < (void *)_end)
return true;
return false;
}
static void print_address_description(void *addr, u8 tag)
{
dump_stack();
pr_err("\n");
if (kernel_or_module_addr(addr)) {
pr_err("The buggy address belongs to the variable:\n");
pr_err(" %pS\n", addr);
}
}
static bool row_is_guilty(const void *row, const void *guilty)
{
return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
}
static int shadow_pointer_offset(const void *row, const void *shadow)
{
/* The length of ">ff00ff00ff00ff00: " is
* 3 + (BITS_PER_LONG/8)*2 chars.
*/
return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
(shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
}
static void print_shadow_for_address(const void *addr)
{
int i;
const void *shadow = kasan_mem_to_shadow(addr);
const void *shadow_row;
shadow_row = (void *)round_down((unsigned long)shadow,
SHADOW_BYTES_PER_ROW)
- SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
pr_err("Memory state around the buggy address:\n");
for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
const void *kaddr = kasan_shadow_to_mem(shadow_row);
char buffer[4 + (BITS_PER_LONG/8)*2];
char shadow_buf[SHADOW_BYTES_PER_ROW];
snprintf(buffer, sizeof(buffer),
(i == 0) ? ">%px: " : " %px: ", kaddr);
/*
* We should not pass a shadow pointer to generic
* function, because generic functions may try to
* access kasan mapping for the passed address.
*/
memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
print_hex_dump(KERN_ERR, buffer,
DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
shadow_buf, SHADOW_BYTES_PER_ROW, 0);
if (row_is_guilty(shadow_row, shadow))
printf("%*c\n",
shadow_pointer_offset(shadow_row, shadow),
'^');
shadow_row += SHADOW_BYTES_PER_ROW;
}
}
static bool report_enabled(void)
{
if (kasan_depth)
return false;
if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
return true;
return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
}
static void __kasan_report(unsigned long addr, size_t size, bool is_write,
unsigned long ip)
{
struct kasan_access_info info;
void *tagged_addr;
void *untagged_addr;
unsigned long flags;
tagged_addr = (void *)addr;
untagged_addr = reset_tag(tagged_addr);
info.access_addr = tagged_addr;
if (addr_has_shadow(untagged_addr))
info.first_bad_addr = find_first_bad_addr(tagged_addr, size);
else
info.first_bad_addr = untagged_addr;
info.access_size = size;
info.is_write = is_write;
info.ip = ip;
start_report(&flags);
print_error_description(&info);
pr_err("\n");
if (addr_has_shadow(untagged_addr)) {
print_address_description(untagged_addr, get_tag(tagged_addr));
pr_err("\n");
print_shadow_for_address(info.first_bad_addr);
} else {
dump_stack();
}
end_report(&flags);
}
bool kasan_report(unsigned long addr, size_t size, bool is_write,
unsigned long ip)
{
bool ret = false;
if (likely(report_enabled())) {
__kasan_report(addr, size, is_write, ip);
ret = true;
}
return ret;
}
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