/*
* This file contains 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 <adech.fo@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 <linux/kernel.h>
#include <linux/mm.h>
#include <linux/printk.h>
#include <linux/sched.h>
#include <linux/slab.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"
/* 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 const void *find_first_bad_addr(const void *addr, size_t size)
{
u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
const void *first_bad_addr = addr;
while (!shadow_val && first_bad_addr < addr + size) {
first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
}
return first_bad_addr;
}
static void print_error_description(struct kasan_access_info *info)
{
const char *bug_type = "unknown-crash";
u8 *shadow_addr;
info->first_bad_addr = find_first_bad_addr(info->access_addr,
info->access_size);
shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
/*
* If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
* at the next shadow byte to determine the type of the bad access.
*/
if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
shadow_addr++;
switch (*shadow_addr) {
case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
/*
* In theory it's still possible to see these shadow values
* due to a data race in the kernel code.
*/
bug_type = "out-of-bounds";
break;
case KASAN_PAGE_REDZONE:
case KASAN_KMALLOC_REDZONE:
bug_type = "slab-out-of-bounds";
break;
case KASAN_GLOBAL_REDZONE:
bug_type = "global-out-of-bounds";
break;
case KASAN_STACK_LEFT:
case KASAN_STACK_MID:
case KASAN_STACK_RIGHT:
case KASAN_STACK_PARTIAL:
bug_type = "stack-out-of-bounds";
break;
case KASAN_FREE_PAGE:
case KASAN_KMALLOC_FREE:
bug_type = "use-after-free";
break;
}
pr_err("BUG: KASAN: %s in %pS at addr %p\n",
bug_type, (void *)info->ip,
info->access_addr);
pr_err("%s of size %zu by task %s/%d\n",
info->is_write ? "Write" : "Read",
info->access_size, current->comm, task_pid_nr(current));
}
static inline bool kernel_or_module_addr(const void *addr)
{
if (addr >= (void *)_stext && addr < (void *)_end)
return true;
if (is_module_address((unsigned long)addr))
return true;
return false;
}
static inline bool init_task_stack_addr(const void *addr)
{
return addr >= (void *)&init_thread_union.stack &&
(addr <= (void *)&init_thread_union.stack +
sizeof(init_thread_union.stack));
}
static void print_address_description(struct kasan_access_info *info)
{
const void *addr = info->access_addr;
if ((addr >= (void *)PAGE_OFFSET) &&
(addr < high_memory)) {
struct page *page = virt_to_head_page(addr);
if (PageSlab(page)) {
void *object;
struct kmem_cache *cache = page->slab_cache;
void *last_object;
object = virt_to_obj(cache, page_address(page), addr);
last_object = page_address(page) +
page->objects * cache->size;
if (unlikely(object > last_object))
object = last_object; /* we hit into padding */
object_err(cache, page, object,
"kasan: bad access detected");
return;
}
dump_page(page, "kasan: bad access detected");
}
if (kernel_or_module_addr(addr)) {
if (!init_task_stack_addr(addr))
pr_err("Address belongs to variable %pS\n", addr);
}
dump_stack();
}
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) ? ">%p: " : " %p: ", 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))
pr_err("%*c\n",
shadow_pointer_offset(shadow_row, shadow),
'^');
shadow_row += SHADOW_BYTES_PER_ROW;
}
}
static DEFINE_SPINLOCK(report_lock);
static void kasan_report_error(struct kasan_access_info *info)
{
unsigned long flags;
const char *bug_type;
/*
* Make sure we don't end up in loop.
*/
kasan_disable_current();
spin_lock_irqsave(&report_lock, flags);
pr_err("================================="
"=================================\n");
if (info->access_addr <
kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
if ((unsigned long)info->access_addr < PAGE_SIZE)
bug_type = "null-ptr-deref";
else if ((unsigned long)info->access_addr < TASK_SIZE)
bug_type = "user-memory-access";
else
bug_type = "wild-memory-access";
pr_err("BUG: KASAN: %s on address %p\n",
bug_type, info->access_addr);
pr_err("%s of size %zu by task %s/%d\n",
info->is_write ? "Write" : "Read",
info->access_size, current->comm,
task_pid_nr(current));
dump_stack();
} else {
print_error_description(info);
print_address_description(info);
print_shadow_for_address(info->first_bad_addr);
}
pr_err("================================="
"=================================\n");
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
spin_unlock_irqrestore(&report_lock, flags);
kasan_enable_current();
}
void kasan_report(unsigned long addr, size_t size,
bool is_write, unsigned long ip)
{
struct kasan_access_info info;
if (likely(!kasan_report_enabled()))
return;
info.access_addr = (void *)addr;
info.access_size = size;
info.is_write = is_write;
info.ip = ip;
kasan_report_error(&info);
}
#define DEFINE_ASAN_REPORT_LOAD(size) \
void __asan_report_load##size##_noabort(unsigned long addr) \
{ \
kasan_report(addr, size, false, _RET_IP_); \
} \
EXPORT_SYMBOL(__asan_report_load##size##_noabort)
#define DEFINE_ASAN_REPORT_STORE(size) \
void __asan_report_store##size##_noabort(unsigned long addr) \
{ \
kasan_report(addr, size, true, _RET_IP_); \
} \
EXPORT_SYMBOL(__asan_report_store##size##_noabort)
DEFINE_ASAN_REPORT_LOAD(1);
DEFINE_ASAN_REPORT_LOAD(2);
DEFINE_ASAN_REPORT_LOAD(4);
DEFINE_ASAN_REPORT_LOAD(8);
DEFINE_ASAN_REPORT_LOAD(16);
DEFINE_ASAN_REPORT_STORE(1);
DEFINE_ASAN_REPORT_STORE(2);
DEFINE_ASAN_REPORT_STORE(4);
DEFINE_ASAN_REPORT_STORE(8);
DEFINE_ASAN_REPORT_STORE(16);
void __asan_report_load_n_noabort(unsigned long addr, size_t size)
{
kasan_report(addr, size, false, _RET_IP_);
}
EXPORT_SYMBOL(__asan_report_load_n_noabort);
void __asan_report_store_n_noabort(unsigned long addr, size_t size)
{
kasan_report(addr, size, true, _RET_IP_);
}
EXPORT_SYMBOL(__asan_report_store_n_noabort);
