linux/mm/kasan/report.c

515 lines
13 KiB
C

// 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 <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 <linux/sched/task_stack.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 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 int __init kasan_set_multi_shot(char *str)
{
set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
return 1;
}
__setup("kasan_multi_shot", kasan_set_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 by task %s/%d\n",
info->is_write ? "Write" : "Read", info->access_size,
info->access_addr, current->comm, task_pid_nr(current));
}
static DEFINE_SPINLOCK(report_lock);
static void start_report(unsigned long *flags)
{
/*
* Make sure we don't end up in loop.
*/
kasan_disable_current();
spin_lock_irqsave(&report_lock, *flags);
pr_err("==================================================================\n");
}
static void end_report(unsigned long *flags)
{
pr_err("==================================================================\n");
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
spin_unlock_irqrestore(&report_lock, *flags);
if (panic_on_warn)
panic("panic_on_warn set ...\n");
kasan_enable_current();
}
static void print_track(struct kasan_track *track, const char *prefix)
{
pr_err("%s by task %u:\n", prefix, track->pid);
if (track->stack) {
unsigned long *entries;
unsigned int nr_entries;
nr_entries = stack_depot_fetch(track->stack, &entries);
stack_trace_print(entries, nr_entries, 0);
} else {
pr_err("(stack is not available)\n");
}
}
struct page *kasan_addr_to_page(const void *addr)
{
if ((addr >= (void *)PAGE_OFFSET) &&
(addr < high_memory))
return virt_to_head_page(addr);
return NULL;
}
static void describe_object_addr(struct kmem_cache *cache, void *object,
const void *addr)
{
unsigned long access_addr = (unsigned long)addr;
unsigned long object_addr = (unsigned long)object;
const char *rel_type;
int rel_bytes;
pr_err("The buggy address belongs to the object at %px\n"
" which belongs to the cache %s of size %d\n",
object, cache->name, cache->object_size);
if (!addr)
return;
if (access_addr < object_addr) {
rel_type = "to the left";
rel_bytes = object_addr - access_addr;
} else if (access_addr >= object_addr + cache->object_size) {
rel_type = "to the right";
rel_bytes = access_addr - (object_addr + cache->object_size);
} else {
rel_type = "inside";
rel_bytes = access_addr - object_addr;
}
pr_err("The buggy address is located %d bytes %s of\n"
" %d-byte region [%px, %px)\n",
rel_bytes, rel_type, cache->object_size, (void *)object_addr,
(void *)(object_addr + cache->object_size));
}
static struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
void *object, u8 tag)
{
struct kasan_alloc_meta *alloc_meta;
int i = 0;
alloc_meta = get_alloc_info(cache, object);
#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
for (i = 0; i < KASAN_NR_FREE_STACKS; i++) {
if (alloc_meta->free_pointer_tag[i] == tag)
break;
}
if (i == KASAN_NR_FREE_STACKS)
i = alloc_meta->free_track_idx;
#endif
return &alloc_meta->free_track[i];
}
static void describe_object(struct kmem_cache *cache, void *object,
const void *addr, u8 tag)
{
struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
if (cache->flags & SLAB_KASAN) {
struct kasan_track *free_track;
print_track(&alloc_info->alloc_track, "Allocated");
pr_err("\n");
free_track = kasan_get_free_track(cache, object, tag);
print_track(free_track, "Freed");
pr_err("\n");
}
describe_object_addr(cache, object, addr);
}
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 bool __must_check tokenize_frame_descr(const char **frame_descr,
char *token, size_t max_tok_len,
unsigned long *value)
{
const char *sep = strchr(*frame_descr, ' ');
if (sep == NULL)
sep = *frame_descr + strlen(*frame_descr);
if (token != NULL) {
const size_t tok_len = sep - *frame_descr;
if (tok_len + 1 > max_tok_len) {
pr_err("KASAN internal error: frame description too long: %s\n",
*frame_descr);
return false;
}
/* Copy token (+ 1 byte for '\0'). */
strlcpy(token, *frame_descr, tok_len + 1);
}
/* Advance frame_descr past separator. */
*frame_descr = sep + 1;
if (value != NULL && kstrtoul(token, 10, value)) {
pr_err("KASAN internal error: not a valid number: %s\n", token);
return false;
}
return true;
}
static void print_decoded_frame_descr(const char *frame_descr)
{
/*
* We need to parse the following string:
* "n alloc_1 alloc_2 ... alloc_n"
* where alloc_i looks like
* "offset size len name"
* or "offset size len name:line".
*/
char token[64];
unsigned long num_objects;
if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
&num_objects))
return;
pr_err("\n");
pr_err("this frame has %lu %s:\n", num_objects,
num_objects == 1 ? "object" : "objects");
while (num_objects--) {
unsigned long offset;
unsigned long size;
/* access offset */
if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
&offset))
return;
/* access size */
if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
&size))
return;
/* name length (unused) */
if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
return;
/* object name */
if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
NULL))
return;
/* Strip line number; without filename it's not very helpful. */
strreplace(token, ':', '\0');
/* Finally, print object information. */
pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
}
}
static bool __must_check get_address_stack_frame_info(const void *addr,
unsigned long *offset,
const char **frame_descr,
const void **frame_pc)
{
unsigned long aligned_addr;
unsigned long mem_ptr;
const u8 *shadow_bottom;
const u8 *shadow_ptr;
const unsigned long *frame;
BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
/*
* NOTE: We currently only support printing frame information for
* accesses to the task's own stack.
*/
if (!object_is_on_stack(addr))
return false;
aligned_addr = round_down((unsigned long)addr, sizeof(long));
mem_ptr = round_down(aligned_addr, KASAN_SHADOW_SCALE_SIZE);
shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
shadow_ptr--;
mem_ptr -= KASAN_SHADOW_SCALE_SIZE;
}
while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
shadow_ptr--;
mem_ptr -= KASAN_SHADOW_SCALE_SIZE;
}
if (shadow_ptr < shadow_bottom)
return false;
frame = (const unsigned long *)(mem_ptr + KASAN_SHADOW_SCALE_SIZE);
if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
frame[0]);
return false;
}
*offset = (unsigned long)addr - (unsigned long)frame;
*frame_descr = (const char *)frame[1];
*frame_pc = (void *)frame[2];
return true;
}
static void print_address_stack_frame(const void *addr)
{
unsigned long offset;
const char *frame_descr;
const void *frame_pc;
if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
return;
if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
&frame_pc))
return;
/*
* get_address_stack_frame_info only returns true if the given addr is
* on the current task's stack.
*/
pr_err("\n");
pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n",
addr, current->comm, task_pid_nr(current), offset);
pr_err(" %pS\n", frame_pc);
if (!frame_descr)
return;
print_decoded_frame_descr(frame_descr);
}
static void print_address_description(void *addr, u8 tag)
{
struct page *page = kasan_addr_to_page(addr);
dump_stack();
pr_err("\n");
if (page && PageSlab(page)) {
struct kmem_cache *cache = page->slab_cache;
void *object = nearest_obj(cache, page, addr);
describe_object(cache, object, addr, tag);
}
if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
pr_err("The buggy address belongs to the variable:\n");
pr_err(" %pS\n", addr);
}
if (page) {
pr_err("The buggy address belongs to the page:\n");
dump_page(page, "kasan: bad access detected");
}
print_address_stack_frame(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))
pr_err("%*c\n",
shadow_pointer_offset(shadow_row, shadow),
'^');
shadow_row += SHADOW_BYTES_PER_ROW;
}
}
static bool report_enabled(void)
{
if (current->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);
}
void kasan_report_invalid_free(void *object, unsigned long ip)
{
unsigned long flags;
u8 tag = get_tag(object);
object = reset_tag(object);
start_report(&flags);
pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
print_tags(tag, object);
pr_err("\n");
print_address_description(object, tag);
pr_err("\n");
print_shadow_for_address(object);
end_report(&flags);
}
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;
if (likely(!report_enabled()))
return;
disable_trace_on_warning();
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);
if (addr_has_shadow(untagged_addr))
print_tags(get_tag(tagged_addr), info.first_bad_addr);
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);
}