linux-stable/mm/kasan/report.c
Alexander Potapenko d3a61f745e kasan: use error_report_end tracepoint
Make it possible to trace KASAN error reporting.  A good usecase is
watching for trace events from the userspace to detect and process memory
corruption reports from the kernel.

Link: https://lkml.kernel.org/r/20210121131915.1331302-4-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Suggested-by: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-02-26 09:41:02 -08:00

463 lines
12 KiB
C

// 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 <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 <linux/uaccess.h>
#include <trace/events/error_report.h>
#include <asm/sections.h>
#include <kunit/test.h>
#include "kasan.h"
#include "../slab.h"
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",
kasan_get_bug_type(info), (void *)info->ip);
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 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, unsigned long addr)
{
trace_error_report_end(ERROR_DETECTOR_KASAN, addr);
pr_err("==================================================================\n");
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
spin_unlock_irqrestore(&report_lock, *flags);
if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
/*
* This thread may hit another WARN() in the panic path.
* Resetting this prevents additional WARN() from panicking the
* system on this thread. Other threads are blocked by the
* panic_mutex in panic().
*/
panic_on_warn = 0;
panic("panic_on_warn set ...\n");
}
#ifdef CONFIG_KASAN_HW_TAGS
if (kasan_flag_panic)
panic("kasan.fault=panic set ...\n");
#endif
kasan_enable_current();
}
static void print_stack(depot_stack_handle_t stack)
{
unsigned long *entries;
unsigned int nr_entries;
nr_entries = stack_depot_fetch(stack, &entries);
stack_trace_print(entries, nr_entries, 0);
}
static void print_track(struct kasan_track *track, const char *prefix)
{
pr_err("%s by task %u:\n", prefix, track->pid);
if (track->stack) {
print_stack(track->stack);
} 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 void describe_object_stacks(struct kmem_cache *cache, void *object,
const void *addr, u8 tag)
{
struct kasan_alloc_meta *alloc_meta;
struct kasan_track *free_track;
alloc_meta = kasan_get_alloc_meta(cache, object);
if (alloc_meta) {
print_track(&alloc_meta->alloc_track, "Allocated");
pr_err("\n");
}
free_track = kasan_get_free_track(cache, object, tag);
if (free_track) {
print_track(free_track, "Freed");
pr_err("\n");
}
#ifdef CONFIG_KASAN_GENERIC
if (!alloc_meta)
return;
if (alloc_meta->aux_stack[0]) {
pr_err("Last potentially related work creation:\n");
print_stack(alloc_meta->aux_stack[0]);
pr_err("\n");
}
if (alloc_meta->aux_stack[1]) {
pr_err("Second to last potentially related work creation:\n");
print_stack(alloc_meta->aux_stack[1]);
pr_err("\n");
}
#endif
}
static void describe_object(struct kmem_cache *cache, void *object,
const void *addr, u8 tag)
{
if (kasan_stack_collection_enabled())
describe_object_stacks(cache, object, addr, tag);
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 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");
}
kasan_print_address_stack_frame(addr);
}
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 bool report_enabled(void)
{
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
if (current->kasan_depth)
return false;
#endif
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_KUNIT)
static void kasan_update_kunit_status(struct kunit *cur_test)
{
struct kunit_resource *resource;
struct kunit_kasan_expectation *kasan_data;
resource = kunit_find_named_resource(cur_test, "kasan_data");
if (!resource) {
kunit_set_failure(cur_test);
return;
}
kasan_data = (struct kunit_kasan_expectation *)resource->data;
WRITE_ONCE(kasan_data->report_found, true);
kunit_put_resource(resource);
}
#endif /* IS_ENABLED(CONFIG_KUNIT) */
void kasan_report_invalid_free(void *object, unsigned long ip)
{
unsigned long flags;
u8 tag = get_tag(object);
object = kasan_reset_tag(object);
#if IS_ENABLED(CONFIG_KUNIT)
if (current->kunit_test)
kasan_update_kunit_status(current->kunit_test);
#endif /* IS_ENABLED(CONFIG_KUNIT) */
start_report(&flags);
pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
kasan_print_tags(tag, object);
pr_err("\n");
print_address_description(object, tag);
pr_err("\n");
print_memory_metadata(object);
end_report(&flags, (unsigned long)object);
}
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;
#if IS_ENABLED(CONFIG_KUNIT)
if (current->kunit_test)
kasan_update_kunit_status(current->kunit_test);
#endif /* IS_ENABLED(CONFIG_KUNIT) */
disable_trace_on_warning();
tagged_addr = (void *)addr;
untagged_addr = kasan_reset_tag(tagged_addr);
info.access_addr = tagged_addr;
if (addr_has_metadata(untagged_addr))
info.first_bad_addr =
kasan_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_metadata(untagged_addr))
kasan_print_tags(get_tag(tagged_addr), info.first_bad_addr);
pr_err("\n");
if (addr_has_metadata(untagged_addr)) {
print_address_description(untagged_addr, get_tag(tagged_addr));
pr_err("\n");
print_memory_metadata(info.first_bad_addr);
} else {
dump_stack();
}
end_report(&flags, addr);
}
bool kasan_report(unsigned long addr, size_t size, bool is_write,
unsigned long ip)
{
unsigned long flags = user_access_save();
bool ret = false;
if (likely(report_enabled())) {
__kasan_report(addr, size, is_write, ip);
ret = true;
}
user_access_restore(flags);
return ret;
}
#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