// SPDX-License-Identifier: GPL-2.0
/*
* This file contains common KASAN error reporting code.
*
* Copyright (c) 2014 Samsung Electronics Co., Ltd.
* Author: Andrey Ryabinin <[email protected]>
*
* Some code borrowed from https://github.com/xairy/kasan-prototype by
* Andrey Konovalov <[email protected]>
*/
#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/vmalloc.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,
KASAN_ARG_FAULT_PANIC_ON_WRITE,
};
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 if (!strcmp(arg, "panic_on_write"))
kasan_arg_fault = KASAN_ARG_FAULT_PANIC_ON_WRITE;
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);
/*
* This function is used to check whether KASAN reports are suppressed for
* software KASAN modes via kasan_disable/enable_current() critical sections.
*
* This is done to avoid:
* 1. False-positive reports when accessing slab metadata,
* 2. Deadlocking when poisoned memory is accessed by the reporting code.
*
* Hardware Tag-Based KASAN instead relies on:
* For #1: Resetting tags via kasan_reset_tag().
* For #2: Suppression of tag checks via CPU, see report_suppress_start/end().
*/
static bool report_suppressed_sw(void)
{
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
if (current->kasan_depth)
return true;
#endif
return false;
}
static void report_suppress_start(void)
{
#ifdef CONFIG_KASAN_HW_TAGS
/*
* Disable preemption for the duration of printing a KASAN report, as
* hw_suppress_tag_checks_start() disables checks on the current CPU.
*/
preempt_disable();
hw_suppress_tag_checks_start();
#else
kasan_disable_current();
#endif
}
static void report_suppress_stop(void)
{
#ifdef CONFIG_KASAN_HW_TAGS
hw_suppress_tag_checks_stop();
preempt_enable();
#else
kasan_enable_current();
#endif
}
/*
* 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. */
report_suppress_start();
spin_lock_irqsave(&report_lock, *flags);
pr_err("==================================================================\n");
}
static void end_report(unsigned long *flags, const void *addr, bool is_write)
{
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");
switch (kasan_arg_fault) {
case KASAN_ARG_FAULT_DEFAULT:
case KASAN_ARG_FAULT_REPORT:
break;
case KASAN_ARG_FAULT_PANIC:
panic("kasan.fault=panic set ...\n");
break;
case KASAN_ARG_FAULT_PANIC_ON_WRITE:
if (is_write)
panic("kasan.fault=panic_on_write set ...\n");
break;
}
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
lockdep_on();
report_suppress_stop();
}
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)
{
#ifdef CONFIG_KASAN_EXTRA_INFO
u64 ts_nsec = track->timestamp;
unsigned long rem_usec;
ts_nsec <<= 9;
rem_usec = do_div(ts_nsec, NSEC_PER_SEC) / 1000;
pr_err("%s by task %u on cpu %d at %lu.%06lus:\n",
prefix, track->pid, track->cpu,
(unsigned long)ts_nsec, rem_usec);
#else
pr_err("%s by task %u:\n", prefix, track->pid);
#endif /* CONFIG_KASAN_EXTRA_INFO */
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 kasan_report_info *info)
{
unsigned long access_addr = (unsigned long)addr;
unsigned long object_addr = (unsigned long)info->object;
const char *rel_type, *region_state = "";
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",
info->object, info->cache->name, info->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 + info->alloc_size) {
rel_type = "to the right";
rel_bytes = access_addr - (object_addr + info->alloc_size);
} else {
rel_type = "inside";
rel_bytes = access_addr - object_addr;
}
/*
* Tag-Based modes use the stack ring to infer the bug type, but the
* memory region state description is generated based on the metadata.
* Thus, defining the region state as below can contradict the metadata.
* Fixing this requires further improvements, so only infer the state
* for the Generic mode.
*/
if (IS_ENABLED(CONFIG_KASAN_GENERIC)) {
if (strcmp(info->bug_type, "slab-out-of-bounds") == 0)
region_state = "allocated ";
else if (strcmp(info->bug_type, "slab-use-after-free") == 0)
region_state = "freed ";
}
pr_err("The buggy address is located %d bytes %s of\n"
" %s%zu-byte region [%px, %px)\n",
rel_bytes, rel_type, region_state, info->alloc_size,
(void *)object_addr, (void *)(object_addr + info->alloc_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);
}
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((void *)info->access_addr);
u8 tag = get_tag((void *)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((void *)info->access_addr);
struct slab *slab;
if (info->type == KASAN_REPORT_ACCESS)
info->first_bad_addr = kasan_find_first_bad_addr(
(void *)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);
/* Try to determine allocation size based on the metadata. */
info->alloc_size = kasan_get_alloc_size(info->object, info->cache);
/* Fallback to the object size if failed. */
if (!info->alloc_size)
info->alloc_size = info->cache->object_size;
} 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_sw(), as an invalid-free cannot be
* caused by accessing poisoned memory and thus should not be suppressed
* by kasan_disable/enable_current() critical sections.
*
* Note that for Hardware Tag-Based KASAN, kasan_report_invalid_free()
* is triggered by explicit tag checks and not by the ones performed by
* the CPU. Thus, reporting invalid-free is not suppressed as well.
*/
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);
/*
* Invalid free is considered a "write" since the allocator's metadata
* updates involves writes.
*/
end_report(&flags, ptr, true);
}
/*
* 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(const void *addr, size_t size, bool is_write,
unsigned long ip)
{
bool ret = true;
unsigned long ua_flags = user_access_save();
unsigned long irq_flags;
struct kasan_report_info info;
if (unlikely(report_suppressed_sw()) || 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 = addr;
info.access_size = size;
info.is_write = is_write;
info.ip = ip;
complete_report_info(&info);
print_report(&info);
end_report(&irq_flags, (void *)addr, is_write);
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_sw(), 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);
/*
* Conservatively set is_write=true, because no details are available.
* In this mode, kasan.fault=panic_on_write is like kasan.fault=panic.
*/
end_report(&flags, NULL, true);
}
#endif /* CONFIG_KASAN_HW_TAGS */
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
/*
* With compiler-based KASAN modes, accesses to bogus pointers (outside of the
* mapped kernel address space regions) cause faults when KASAN tries to check
* the shadow memory before the actual memory access. This results in cryptic
* GPF reports, which are hard for users to interpret. This hook helps users to
* figure out what the original bogus pointer was.
*/
void kasan_non_canonical_hook(unsigned long addr)
{
unsigned long orig_addr;
const char *bug_type;
/*
* All addresses that came as a result of the memory-to-shadow mapping
* (even for bogus pointers) must be >= KASAN_SHADOW_OFFSET.
*/
if (addr < KASAN_SHADOW_OFFSET)
return;
orig_addr = (unsigned long)kasan_shadow_to_mem((void *)addr);
/*
* 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 the shadow for low or high canonical
* addresses, we can still be pretty sure: these shadow regions are a
* fairly narrow chunk of the address space.
* But the shadow for non-canonical addresses is a really large chunk
* of the address space. For this 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 if (addr_in_shadow((void *)addr))
bug_type = "probably wild-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
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