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// SPDX-License-Identifier: GPL-2.0
/*
* This file contains common 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>
*/
#include <kunit/test.h>
#include <linux/bitops.h>
#include <linux/ftrace.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/lockdep.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 <linux/uaccess.h>
#include <trace/events/error_report.h>
#include <asm/sections.h>
#include "kasan.h"
#include "../slab.h"
static unsigned long kasan_flags;
#define KASAN_BIT_REPORTED 0
#define KASAN_BIT_MULTI_SHOT 1
enum kasan_arg_fault {
KASAN_ARG_FAULT_DEFAULT,
KASAN_ARG_FAULT_REPORT,
KASAN_ARG_FAULT_PANIC,
};
static enum kasan_arg_fault kasan_arg_fault __ro_after_init = KASAN_ARG_FAULT_DEFAULT;
/* kasan.fault=report/panic */
static int __init early_kasan_fault(char *arg)
{
if (!arg)
return -EINVAL;
if (!strcmp(arg, "report"))
kasan_arg_fault = KASAN_ARG_FAULT_REPORT;
else if (!strcmp(arg, "panic"))
kasan_arg_fault = KASAN_ARG_FAULT_PANIC;
else
return -EINVAL;
return 0;
}
early_param("kasan.fault", early_kasan_fault);
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);
/*
* Used to suppress reports within kasan_disable/enable_current() critical
* sections, which are used for marking accesses to slab metadata.
*/
static bool report_suppressed(void)
{
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
if (current->kasan_depth)
return true;
#endif
return false;
}
/*
* Used to avoid reporting more than one KASAN bug unless kasan_multi_shot
* is enabled. Note that KASAN tests effectively enable kasan_multi_shot
* for their duration.
*/
static bool report_enabled(void)
{
if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
return true;
return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
}
#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST)
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);
#endif
#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
/*
* Whether the KASAN KUnit test suite is currently being executed.
* Updated in kasan_test.c.
*/
static bool kasan_kunit_executing;
void kasan_kunit_test_suite_start(void)
{
WRITE_ONCE(kasan_kunit_executing, true);
}
EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_start);
void kasan_kunit_test_suite_end(void)
{
WRITE_ONCE(kasan_kunit_executing, false);
}
EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_end);
static bool kasan_kunit_test_suite_executing(void)
{
return READ_ONCE(kasan_kunit_executing);
}
#else /* CONFIG_KASAN_KUNIT_TEST */
static inline bool kasan_kunit_test_suite_executing(void) { return false; }
#endif /* CONFIG_KASAN_KUNIT_TEST */
#if IS_ENABLED(CONFIG_KUNIT)
static void fail_non_kasan_kunit_test(void)
{
struct kunit *test;
if (kasan_kunit_test_suite_executing())
return;
test = current->kunit_test;
if (test)
kunit_set_failure(test);
}
#else /* CONFIG_KUNIT */
static inline void fail_non_kasan_kunit_test(void) { }
#endif /* CONFIG_KUNIT */
static DEFINE_SPINLOCK(report_lock);
static void start_report(unsigned long *flags, bool sync)
{
fail_non_kasan_kunit_test();
/* Respect the /proc/sys/kernel/traceoff_on_warning interface. */
disable_trace_on_warning();
/* Do not allow LOCKDEP mangling KASAN reports. */
lockdep_off();
/* 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, void *addr)
{
if (addr)
trace_error_report_end(ERROR_DETECTOR_KASAN,
(unsigned long)addr);
pr_err("==================================================================\n");
spin_unlock_irqrestore(&report_lock, *flags);
if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
check_panic_on_warn("KASAN");
if (kasan_arg_fault == KASAN_ARG_FAULT_PANIC)
panic("kasan.fault=panic set ...\n");
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
lockdep_on();
kasan_enable_current();
}
static void print_error_description(struct kasan_report_info *info)
{
pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip);
if (info->type != KASAN_REPORT_ACCESS) {
pr_err("Free of addr %px by task %s/%d\n",
info->access_addr, current->comm, task_pid_nr(current));
return;
}
if (info->access_size)
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));
else
pr_err("%s at addr %px by task %s/%d\n",
info->is_write ? "Write" : "Read",
info->access_addr, current->comm, task_pid_nr(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)
stack_depot_print(track->stack);
else
pr_err("(stack is not available)\n");
}
static inline struct page *addr_to_page(const void *addr)
{
if (virt_addr_valid(addr))
return virt_to_head_page(addr);
return NULL;
}
static void describe_object_addr(const void *addr, struct kmem_cache *cache,
void *object)
{
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 (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 void describe_object_stacks(struct kasan_report_info *info)
{
if (info->alloc_track.stack) {
print_track(&info->alloc_track, "Allocated");
pr_err("\n");
}
if (info->free_track.stack) {
print_track(&info->free_track, "Freed");
pr_err("\n");
}
kasan_print_aux_stacks(info->cache, info->object);
}
static void describe_object(const void *addr, struct kasan_report_info *info)
{
if (kasan_stack_collection_enabled())
describe_object_stacks(info);
describe_object_addr(addr, info->cache, info->object);
}
static inline bool kernel_or_module_addr(const void *addr)
{
if (is_kernel((unsigned long)addr))
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(void *addr, u8 tag,
struct kasan_report_info *info)
{
struct page *page = addr_to_page(addr);
dump_stack_lvl(KERN_ERR);
pr_err("\n");
if (info->cache && info->object) {
describe_object(addr, info);
pr_err("\n");
}
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);
pr_err("\n");
}
if (object_is_on_stack(addr)) {
/*
* Currently, KASAN supports printing frame information only
* for accesses to the task's own stack.
*/
kasan_print_address_stack_frame(addr);
pr_err("\n");
}
if (is_vmalloc_addr(addr)) {
struct vm_struct *va = find_vm_area(addr);
if (va) {
pr_err("The buggy address belongs to the virtual mapping at\n"
" [%px, %px) created by:\n"
" %pS\n",
va->addr, va->addr + va->size, va->caller);
pr_err("\n");
page = vmalloc_to_page(addr);
}
}
if (page) {
pr_err("The buggy address belongs to the physical page:\n");
dump_page(page, "kasan: bad access detected");
pr_err("\n");
}
}
static bool meta_row_is_guilty(const void *row, const void *addr)
{
return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
}
static int meta_pointer_offset(const void *row, const void *addr)
{
/*
* Memory state around the buggy address:
* ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
* ...
*
* The length of ">ff00ff00ff00ff00: " is
* 3 + (BITS_PER_LONG / 8) * 2 chars.
* The length of each granule metadata is 2 bytes
* plus 1 byte for space.
*/
return 3 + (BITS_PER_LONG / 8) * 2 +
(addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
}
static void print_memory_metadata(const void *addr)
{
int i;
void *row;
row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
- META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
pr_err("Memory state around the buggy address:\n");
for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
char buffer[4 + (BITS_PER_LONG / 8) * 2];
char metadata[META_BYTES_PER_ROW];
snprintf(buffer, sizeof(buffer),
(i == 0) ? ">%px: " : " %px: ", row);
/*
* We should not pass a shadow pointer to generic
* function, because generic functions may try to
* access kasan mapping for the passed address.
*/
kasan_metadata_fetch_row(&metadata[0], row);
print_hex_dump(KERN_ERR, buffer,
DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
metadata, META_BYTES_PER_ROW, 0);
if (meta_row_is_guilty(row, addr))
pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
row += META_MEM_BYTES_PER_ROW;
}
}
static void print_report(struct kasan_report_info *info)
{
void *addr = kasan_reset_tag(info->access_addr);
u8 tag = get_tag(info->access_addr);
print_error_description(info);
if (addr_has_metadata(addr))
kasan_print_tags(tag, info->first_bad_addr);
pr_err("\n");
if (addr_has_metadata(addr)) {
print_address_description(addr, tag, info);
print_memory_metadata(info->first_bad_addr);
} else {
dump_stack_lvl(KERN_ERR);
}
}
static void complete_report_info(struct kasan_report_info *info)
{
void *addr = kasan_reset_tag(info->access_addr);
struct slab *slab;
if (info->type == KASAN_REPORT_ACCESS)
info->first_bad_addr = kasan_find_first_bad_addr(
info->access_addr, info->access_size);
else
info->first_bad_addr = addr;
slab = kasan_addr_to_slab(addr);
if (slab) {
info->cache = slab->slab_cache;
info->object = nearest_obj(info->cache, slab, addr);
} else
info->cache = info->object = NULL;
switch (info->type) {
case KASAN_REPORT_INVALID_FREE:
info->bug_type = "invalid-free";
break;
case KASAN_REPORT_DOUBLE_FREE:
info->bug_type = "double-free";
break;
default:
/* bug_type filled in by kasan_complete_mode_report_info. */
break;
}
/* Fill in mode-specific report info fields. */
kasan_complete_mode_report_info(info);
}
void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type)
{
unsigned long flags;
struct kasan_report_info info;
/*
* Do not check report_suppressed(), as an invalid-free cannot be
* caused by accessing slab metadata and thus should not be
* suppressed by kasan_disable/enable_current() critical sections.
*/
if (unlikely(!report_enabled()))
return;
start_report(&flags, true);
memset(&info, 0, sizeof(info));
info.type = type;
info.access_addr = ptr;
info.access_size = 0;
info.is_write = false;
info.ip = ip;
complete_report_info(&info);
print_report(&info);
end_report(&flags, ptr);
}
/*
* kasan_report() is the only reporting function that uses
* user_access_save/restore(): kasan_report_invalid_free() cannot be called
* from a UACCESS region, and kasan_report_async() is not used on x86.
*/
bool kasan_report(unsigned long addr, size_t size, bool is_write,
unsigned long ip)
{
bool ret = true;
void *ptr = (void *)addr;
unsigned long ua_flags = user_access_save();
unsigned long irq_flags;
struct kasan_report_info info;
if (unlikely(report_suppressed()) || unlikely(!report_enabled())) {
ret = false;
goto out;
}
start_report(&irq_flags, true);
memset(&info, 0, sizeof(info));
info.type = KASAN_REPORT_ACCESS;
info.access_addr = ptr;
info.access_size = size;
info.is_write = is_write;
info.ip = ip;
complete_report_info(&info);
print_report(&info);
end_report(&irq_flags, ptr);
out:
user_access_restore(ua_flags);
return ret;
}
#ifdef CONFIG_KASAN_HW_TAGS
void kasan_report_async(void)
{
unsigned long flags;
/*
* Do not check report_suppressed(), as kasan_disable/enable_current()
* critical sections do not affect Hardware Tag-Based KASAN.
*/
if (unlikely(!report_enabled()))
return;
start_report(&flags, false);
pr_err("BUG: KASAN: invalid-access\n");
pr_err("Asynchronous fault: no details available\n");
pr_err("\n");
dump_stack_lvl(KERN_ERR);
end_report(&flags, NULL);
}
#endif /* CONFIG_KASAN_HW_TAGS */
#ifdef CONFIG_KASAN_INLINE
/*
* With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
* canonical half of the address space) cause out-of-bounds shadow memory reads
* before the actual access. For addresses in the low canonical half of the
* address space, as well as most non-canonical addresses, that out-of-bounds
* shadow memory access lands in the non-canonical part of the address space.
* Help the user figure out what the original bogus pointer was.
*/
void kasan_non_canonical_hook(unsigned long addr)
{
unsigned long orig_addr;
const char *bug_type;
if (addr < KASAN_SHADOW_OFFSET)
return;
orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
/*
* For faults near the shadow address for NULL, we can be fairly certain
* that this is a KASAN shadow memory access.
* For faults that correspond to shadow for low canonical addresses, we
* can still be pretty sure - that shadow region is a fairly narrow
* chunk of the non-canonical address space.
* But faults that look like shadow for non-canonical addresses are a
* really large chunk of the address space. In that case, we still
* print the decoded address, but make it clear that this is not
* necessarily what's actually going on.
*/
if (orig_addr < PAGE_SIZE)
bug_type = "null-ptr-deref";
else if (orig_addr < TASK_SIZE)
bug_type = "probably user-memory-access";
else
bug_type = "maybe wild-memory-access";
pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
}
#endif