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![Kuan-Ying Lee](/assets/img/avatar_default.png)
Currently, KASAN describes all invalid-free/double-free bugs as "double-free or invalid-free". This is ambiguous. KASAN should report "double-free" when a double-free is a more likely cause (the address points to the start of an object) and report "invalid-free" otherwise [1]. [1] https://bugzilla.kernel.org/show_bug.cgi?id=212193 Link: https://lkml.kernel.org/r/20220615062219.22618-1-Kuan-Ying.Lee@mediatek.com Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Matthias Brugger <matthias.bgg@gmail.com> Cc: Chinwen Chang <chinwen.chang@mediatek.com> Cc: Yee Lee <yee.lee@mediatek.com> Cc: Andrew Yang <andrew.yang@mediatek.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
564 lines
15 KiB
C
564 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* This file contains common KASAN error reporting code.
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*
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* Copyright (c) 2014 Samsung Electronics Co., Ltd.
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* Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
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*
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* Some code borrowed from https://github.com/xairy/kasan-prototype by
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* Andrey Konovalov <andreyknvl@gmail.com>
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*/
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#include <linux/bitops.h>
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#include <linux/ftrace.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/lockdep.h>
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#include <linux/mm.h>
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#include <linux/printk.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/stackdepot.h>
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#include <linux/stacktrace.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/kasan.h>
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#include <linux/module.h>
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#include <linux/sched/task_stack.h>
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#include <linux/uaccess.h>
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#include <trace/events/error_report.h>
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#include <asm/sections.h>
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#include <kunit/test.h>
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#include "kasan.h"
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#include "../slab.h"
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static unsigned long kasan_flags;
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#define KASAN_BIT_REPORTED 0
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#define KASAN_BIT_MULTI_SHOT 1
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enum kasan_arg_fault {
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KASAN_ARG_FAULT_DEFAULT,
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KASAN_ARG_FAULT_REPORT,
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KASAN_ARG_FAULT_PANIC,
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};
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static enum kasan_arg_fault kasan_arg_fault __ro_after_init = KASAN_ARG_FAULT_DEFAULT;
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/* kasan.fault=report/panic */
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static int __init early_kasan_fault(char *arg)
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{
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if (!arg)
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return -EINVAL;
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if (!strcmp(arg, "report"))
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kasan_arg_fault = KASAN_ARG_FAULT_REPORT;
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else if (!strcmp(arg, "panic"))
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kasan_arg_fault = KASAN_ARG_FAULT_PANIC;
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else
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return -EINVAL;
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return 0;
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}
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early_param("kasan.fault", early_kasan_fault);
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static int __init kasan_set_multi_shot(char *str)
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{
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set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
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return 1;
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}
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__setup("kasan_multi_shot", kasan_set_multi_shot);
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/*
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* Used to suppress reports within kasan_disable/enable_current() critical
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* sections, which are used for marking accesses to slab metadata.
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*/
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static bool report_suppressed(void)
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{
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#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
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if (current->kasan_depth)
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return true;
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#endif
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return false;
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}
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/*
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* Used to avoid reporting more than one KASAN bug unless kasan_multi_shot
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* is enabled. Note that KASAN tests effectively enable kasan_multi_shot
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* for their duration.
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*/
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static bool report_enabled(void)
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{
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if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
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return true;
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return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
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}
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#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST)
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bool kasan_save_enable_multi_shot(void)
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{
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return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
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}
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EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
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void kasan_restore_multi_shot(bool enabled)
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{
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if (!enabled)
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clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
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}
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EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
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#endif
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#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
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static void update_kunit_status(bool sync)
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{
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struct kunit *test;
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struct kunit_resource *resource;
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struct kunit_kasan_status *status;
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test = current->kunit_test;
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if (!test)
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return;
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resource = kunit_find_named_resource(test, "kasan_status");
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if (!resource) {
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kunit_set_failure(test);
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return;
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}
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status = (struct kunit_kasan_status *)resource->data;
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WRITE_ONCE(status->report_found, true);
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WRITE_ONCE(status->sync_fault, sync);
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kunit_put_resource(resource);
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}
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#else
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static void update_kunit_status(bool sync) { }
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#endif
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static DEFINE_SPINLOCK(report_lock);
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static void start_report(unsigned long *flags, bool sync)
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{
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/* Respect the /proc/sys/kernel/traceoff_on_warning interface. */
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disable_trace_on_warning();
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/* Update status of the currently running KASAN test. */
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update_kunit_status(sync);
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/* Do not allow LOCKDEP mangling KASAN reports. */
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lockdep_off();
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/* Make sure we don't end up in loop. */
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kasan_disable_current();
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spin_lock_irqsave(&report_lock, *flags);
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pr_err("==================================================================\n");
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}
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static void end_report(unsigned long *flags, void *addr)
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{
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if (addr)
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trace_error_report_end(ERROR_DETECTOR_KASAN,
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(unsigned long)addr);
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pr_err("==================================================================\n");
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spin_unlock_irqrestore(&report_lock, *flags);
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if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
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panic("panic_on_warn set ...\n");
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if (kasan_arg_fault == KASAN_ARG_FAULT_PANIC)
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panic("kasan.fault=panic set ...\n");
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add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
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lockdep_on();
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kasan_enable_current();
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}
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static void print_error_description(struct kasan_report_info *info)
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{
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if (info->type == KASAN_REPORT_INVALID_FREE) {
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pr_err("BUG: KASAN: invalid-free in %pS\n", (void *)info->ip);
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return;
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}
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if (info->type == KASAN_REPORT_DOUBLE_FREE) {
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pr_err("BUG: KASAN: double-free in %pS\n", (void *)info->ip);
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return;
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}
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pr_err("BUG: KASAN: %s in %pS\n",
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kasan_get_bug_type(info), (void *)info->ip);
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if (info->access_size)
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pr_err("%s of size %zu at addr %px by task %s/%d\n",
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info->is_write ? "Write" : "Read", info->access_size,
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info->access_addr, current->comm, task_pid_nr(current));
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else
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pr_err("%s at addr %px by task %s/%d\n",
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info->is_write ? "Write" : "Read",
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info->access_addr, current->comm, task_pid_nr(current));
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}
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static void print_track(struct kasan_track *track, const char *prefix)
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{
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pr_err("%s by task %u:\n", prefix, track->pid);
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if (track->stack) {
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stack_depot_print(track->stack);
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} else {
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pr_err("(stack is not available)\n");
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}
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}
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struct page *kasan_addr_to_page(const void *addr)
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{
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if ((addr >= (void *)PAGE_OFFSET) &&
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(addr < high_memory))
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return virt_to_head_page(addr);
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return NULL;
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}
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struct slab *kasan_addr_to_slab(const void *addr)
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{
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if ((addr >= (void *)PAGE_OFFSET) &&
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(addr < high_memory))
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return virt_to_slab(addr);
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return NULL;
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}
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static void describe_object_addr(struct kmem_cache *cache, void *object,
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const void *addr)
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{
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unsigned long access_addr = (unsigned long)addr;
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unsigned long object_addr = (unsigned long)object;
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const char *rel_type;
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int rel_bytes;
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pr_err("The buggy address belongs to the object at %px\n"
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" which belongs to the cache %s of size %d\n",
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object, cache->name, cache->object_size);
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if (access_addr < object_addr) {
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rel_type = "to the left";
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rel_bytes = object_addr - access_addr;
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} else if (access_addr >= object_addr + cache->object_size) {
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rel_type = "to the right";
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rel_bytes = access_addr - (object_addr + cache->object_size);
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} else {
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rel_type = "inside";
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rel_bytes = access_addr - object_addr;
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}
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pr_err("The buggy address is located %d bytes %s of\n"
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" %d-byte region [%px, %px)\n",
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rel_bytes, rel_type, cache->object_size, (void *)object_addr,
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(void *)(object_addr + cache->object_size));
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}
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static void describe_object_stacks(struct kmem_cache *cache, void *object,
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const void *addr, u8 tag)
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{
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struct kasan_alloc_meta *alloc_meta;
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struct kasan_track *free_track;
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alloc_meta = kasan_get_alloc_meta(cache, object);
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if (alloc_meta) {
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print_track(&alloc_meta->alloc_track, "Allocated");
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pr_err("\n");
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}
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free_track = kasan_get_free_track(cache, object, tag);
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if (free_track) {
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print_track(free_track, "Freed");
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pr_err("\n");
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}
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#ifdef CONFIG_KASAN_GENERIC
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if (!alloc_meta)
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return;
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if (alloc_meta->aux_stack[0]) {
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pr_err("Last potentially related work creation:\n");
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stack_depot_print(alloc_meta->aux_stack[0]);
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pr_err("\n");
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}
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if (alloc_meta->aux_stack[1]) {
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pr_err("Second to last potentially related work creation:\n");
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stack_depot_print(alloc_meta->aux_stack[1]);
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pr_err("\n");
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}
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#endif
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}
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static void describe_object(struct kmem_cache *cache, void *object,
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const void *addr, u8 tag)
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{
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if (kasan_stack_collection_enabled())
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describe_object_stacks(cache, object, addr, tag);
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describe_object_addr(cache, object, addr);
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}
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static inline bool kernel_or_module_addr(const void *addr)
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{
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if (is_kernel((unsigned long)addr))
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return true;
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if (is_module_address((unsigned long)addr))
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return true;
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return false;
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}
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static inline bool init_task_stack_addr(const void *addr)
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{
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return addr >= (void *)&init_thread_union.stack &&
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(addr <= (void *)&init_thread_union.stack +
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sizeof(init_thread_union.stack));
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}
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static void print_address_description(void *addr, u8 tag)
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{
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struct page *page = kasan_addr_to_page(addr);
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dump_stack_lvl(KERN_ERR);
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pr_err("\n");
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if (page && PageSlab(page)) {
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struct slab *slab = page_slab(page);
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struct kmem_cache *cache = slab->slab_cache;
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void *object = nearest_obj(cache, slab, addr);
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describe_object(cache, object, addr, tag);
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pr_err("\n");
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}
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if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
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pr_err("The buggy address belongs to the variable:\n");
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pr_err(" %pS\n", addr);
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pr_err("\n");
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}
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if (object_is_on_stack(addr)) {
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/*
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* Currently, KASAN supports printing frame information only
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* for accesses to the task's own stack.
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*/
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kasan_print_address_stack_frame(addr);
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pr_err("\n");
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}
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if (is_vmalloc_addr(addr)) {
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struct vm_struct *va = find_vm_area(addr);
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if (va) {
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pr_err("The buggy address belongs to the virtual mapping at\n"
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" [%px, %px) created by:\n"
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" %pS\n",
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va->addr, va->addr + va->size, va->caller);
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pr_err("\n");
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page = vmalloc_to_page(addr);
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}
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}
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if (page) {
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pr_err("The buggy address belongs to the physical page:\n");
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dump_page(page, "kasan: bad access detected");
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pr_err("\n");
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}
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}
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static bool meta_row_is_guilty(const void *row, const void *addr)
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{
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return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
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}
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static int meta_pointer_offset(const void *row, const void *addr)
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{
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/*
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* Memory state around the buggy address:
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* ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
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* ...
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*
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* The length of ">ff00ff00ff00ff00: " is
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* 3 + (BITS_PER_LONG / 8) * 2 chars.
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* The length of each granule metadata is 2 bytes
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* plus 1 byte for space.
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*/
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return 3 + (BITS_PER_LONG / 8) * 2 +
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(addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
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}
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static void print_memory_metadata(const void *addr)
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{
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int i;
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void *row;
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row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
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- META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
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pr_err("Memory state around the buggy address:\n");
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for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
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char buffer[4 + (BITS_PER_LONG / 8) * 2];
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char metadata[META_BYTES_PER_ROW];
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snprintf(buffer, sizeof(buffer),
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(i == 0) ? ">%px: " : " %px: ", row);
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/*
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* We should not pass a shadow pointer to generic
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* function, because generic functions may try to
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* access kasan mapping for the passed address.
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*/
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kasan_metadata_fetch_row(&metadata[0], row);
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print_hex_dump(KERN_ERR, buffer,
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DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
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metadata, META_BYTES_PER_ROW, 0);
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if (meta_row_is_guilty(row, addr))
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pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
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row += META_MEM_BYTES_PER_ROW;
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}
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}
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static void print_report(struct kasan_report_info *info)
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{
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void *tagged_addr = info->access_addr;
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void *untagged_addr = kasan_reset_tag(tagged_addr);
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u8 tag = get_tag(tagged_addr);
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print_error_description(info);
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if (addr_has_metadata(untagged_addr))
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kasan_print_tags(tag, info->first_bad_addr);
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pr_err("\n");
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if (addr_has_metadata(untagged_addr)) {
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print_address_description(untagged_addr, tag);
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print_memory_metadata(info->first_bad_addr);
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} else {
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dump_stack_lvl(KERN_ERR);
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}
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}
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void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type)
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{
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unsigned long flags;
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struct kasan_report_info info;
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/*
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* Do not check report_suppressed(), as an invalid-free cannot be
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* caused by accessing slab metadata and thus should not be
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* suppressed by kasan_disable/enable_current() critical sections.
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*/
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if (unlikely(!report_enabled()))
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return;
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start_report(&flags, true);
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info.type = type;
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info.access_addr = ptr;
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info.first_bad_addr = kasan_reset_tag(ptr);
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info.access_size = 0;
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info.is_write = false;
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info.ip = ip;
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print_report(&info);
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end_report(&flags, ptr);
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}
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/*
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* kasan_report() is the only reporting function that uses
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* user_access_save/restore(): kasan_report_invalid_free() cannot be called
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* from a UACCESS region, and kasan_report_async() is not used on x86.
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*/
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bool kasan_report(unsigned long addr, size_t size, bool is_write,
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unsigned long ip)
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{
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bool ret = true;
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void *ptr = (void *)addr;
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unsigned long ua_flags = user_access_save();
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unsigned long irq_flags;
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struct kasan_report_info info;
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if (unlikely(report_suppressed()) || unlikely(!report_enabled())) {
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ret = false;
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goto out;
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}
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start_report(&irq_flags, true);
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|
|
info.type = KASAN_REPORT_ACCESS;
|
|
info.access_addr = ptr;
|
|
info.first_bad_addr = kasan_find_first_bad_addr(ptr, size);
|
|
info.access_size = size;
|
|
info.is_write = is_write;
|
|
info.ip = ip;
|
|
|
|
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
|