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![Andrey Konovalov](/assets/img/avatar_default.png)
KASAN marks caches that are sanitized with the SLAB_KASAN cache flag. Currently if the metadata that is appended after the object (stores e.g. stack trace ids) doesn't fit into KMALLOC_MAX_SIZE (can only happen with SLAB, see the comment in the patch), KASAN turns off sanitization completely. With this change sanitization of the object data is always enabled. However the metadata is only stored when it fits. Instead of checking for SLAB_KASAN flag accross the code to find out whether the metadata is there, use cache->kasan_info.alloc/free_meta_offset. As 0 can be a valid value for free_meta_offset, introduce KASAN_NO_FREE_META as an indicator that the free metadata is missing. Without this change all sanitized KASAN objects would be put into quarantine with generic KASAN. With this change, only the objects that have metadata (i.e. when it fits) are put into quarantine, the rest is freed right away. Along the way rework __kasan_cache_create() and add claryfying comments. Link: https://lkml.kernel.org/r/aee34b87a5e4afe586c2ac6a0b32db8dc4dcc2dc.1606162397.git.andreyknvl@google.com Link: https://linux-review.googlesource.com/id/Icd947e2bea054cb5cfbdc6cf6652227d97032dcb Co-developed-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com> Signed-off-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com> Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Marco Elver <elver@google.com> Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Branislav Rankov <Branislav.Rankov@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Kevin Brodsky <kevin.brodsky@arm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
460 lines
12 KiB
C
460 lines
12 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/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 <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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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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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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static void print_error_description(struct kasan_access_info *info)
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{
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pr_err("BUG: KASAN: %s in %pS\n",
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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 DEFINE_SPINLOCK(report_lock);
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static void start_report(unsigned long *flags)
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{
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/*
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* Make sure we don't end up in loop.
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*/
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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)
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{
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pr_err("==================================================================\n");
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add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
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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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/*
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* This thread may hit another WARN() in the panic path.
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* Resetting this prevents additional WARN() from panicking the
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* system on this thread. Other threads are blocked by the
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* panic_mutex in panic().
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*/
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panic_on_warn = 0;
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panic("panic_on_warn set ...\n");
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}
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#ifdef CONFIG_KASAN_HW_TAGS
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if (kasan_flag_panic)
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panic("kasan.fault=panic set ...\n");
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#endif
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kasan_enable_current();
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}
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static void print_stack(depot_stack_handle_t stack)
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{
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unsigned long *entries;
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unsigned int nr_entries;
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nr_entries = stack_depot_fetch(stack, &entries);
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stack_trace_print(entries, nr_entries, 0);
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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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print_stack(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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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 (!addr)
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return;
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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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print_stack(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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print_stack(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 (addr >= (void *)_stext && addr < (void *)_end)
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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();
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pr_err("\n");
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if (page && PageSlab(page)) {
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struct kmem_cache *cache = page->slab_cache;
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void *object = nearest_obj(cache, page, addr);
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describe_object(cache, object, addr, tag);
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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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}
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if (page) {
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pr_err("The buggy address belongs to the page:\n");
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dump_page(page, "kasan: bad access detected");
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}
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print_address_stack_frame(addr);
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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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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 bool report_enabled(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 false;
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#endif
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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_KUNIT)
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static void kasan_update_kunit_status(struct kunit *cur_test)
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{
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struct kunit_resource *resource;
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struct kunit_kasan_expectation *kasan_data;
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resource = kunit_find_named_resource(cur_test, "kasan_data");
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if (!resource) {
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kunit_set_failure(cur_test);
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return;
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}
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kasan_data = (struct kunit_kasan_expectation *)resource->data;
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kasan_data->report_found = true;
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kunit_put_resource(resource);
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}
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#endif /* IS_ENABLED(CONFIG_KUNIT) */
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void kasan_report_invalid_free(void *object, unsigned long ip)
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{
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unsigned long flags;
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u8 tag = get_tag(object);
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object = kasan_reset_tag(object);
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#if IS_ENABLED(CONFIG_KUNIT)
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if (current->kunit_test)
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kasan_update_kunit_status(current->kunit_test);
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#endif /* IS_ENABLED(CONFIG_KUNIT) */
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start_report(&flags);
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pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
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print_tags(tag, object);
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pr_err("\n");
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print_address_description(object, tag);
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pr_err("\n");
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print_memory_metadata(object);
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end_report(&flags);
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}
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static void __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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struct kasan_access_info info;
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void *tagged_addr;
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void *untagged_addr;
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unsigned long flags;
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#if IS_ENABLED(CONFIG_KUNIT)
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if (current->kunit_test)
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kasan_update_kunit_status(current->kunit_test);
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#endif /* IS_ENABLED(CONFIG_KUNIT) */
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disable_trace_on_warning();
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tagged_addr = (void *)addr;
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untagged_addr = kasan_reset_tag(tagged_addr);
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info.access_addr = tagged_addr;
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if (addr_has_metadata(untagged_addr))
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info.first_bad_addr = find_first_bad_addr(tagged_addr, size);
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else
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info.first_bad_addr = untagged_addr;
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info.access_size = size;
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info.is_write = is_write;
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info.ip = ip;
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start_report(&flags);
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print_error_description(&info);
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if (addr_has_metadata(untagged_addr))
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print_tags(get_tag(tagged_addr), 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, get_tag(tagged_addr));
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pr_err("\n");
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print_memory_metadata(info.first_bad_addr);
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} else {
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dump_stack();
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}
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end_report(&flags);
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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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unsigned long flags = user_access_save();
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bool ret = false;
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if (likely(report_enabled())) {
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__kasan_report(addr, size, is_write, ip);
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ret = true;
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}
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user_access_restore(flags);
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return ret;
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}
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#ifdef CONFIG_KASAN_INLINE
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/*
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* With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
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* canonical half of the address space) cause out-of-bounds shadow memory reads
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* before the actual access. For addresses in the low canonical half of the
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* address space, as well as most non-canonical addresses, that out-of-bounds
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* shadow memory access lands in the non-canonical part of the address space.
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* Help the user figure out what the original bogus pointer was.
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*/
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void kasan_non_canonical_hook(unsigned long addr)
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{
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unsigned long orig_addr;
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const char *bug_type;
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if (addr < KASAN_SHADOW_OFFSET)
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return;
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orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
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/*
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* For faults near the shadow address for NULL, we can be fairly certain
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* that this is a KASAN shadow memory access.
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* For faults that correspond to shadow for low canonical addresses, we
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* can still be pretty sure - that shadow region is a fairly narrow
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* chunk of the non-canonical address space.
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* But faults that look like shadow for non-canonical addresses are a
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* really large chunk of the address space. In that case, we still
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* print the decoded address, but make it clear that this is not
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* necessarily what's actually going on.
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*/
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if (orig_addr < PAGE_SIZE)
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bug_type = "null-ptr-deref";
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else if (orig_addr < TASK_SIZE)
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bug_type = "probably user-memory-access";
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else
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bug_type = "maybe wild-memory-access";
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pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
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orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
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}
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#endif
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