![Marco Elver](/assets/img/avatar_default.png)
This adds support for printing stack frame description on invalid stack accesses. The frame description is embedded by the compiler, which is parsed and then pretty-printed. Currently, we can only print the stack frame info for accesses to the task's own stack, but not accesses to other tasks' stacks. Example of what it looks like: page dumped because: kasan: bad access detected addr ffff8880673ef98a is located in stack of task insmod/2008 at offset 106 in frame: kasan_stack_oob+0x0/0xf5 [test_kasan] this frame has 2 objects: [32, 36) 'i' [96, 106) 'stack_array' Memory state around the buggy address: Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=198435 Link: http://lkml.kernel.org/r/20190522100048.146841-1-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
491 lines
12 KiB
C
491 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* This file contains common generic and tag-based 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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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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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 <asm/sections.h>
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#include "kasan.h"
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#include "../slab.h"
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/* Shadow layout customization. */
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#define SHADOW_BYTES_PER_BLOCK 1
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#define SHADOW_BLOCKS_PER_ROW 16
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#define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
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#define SHADOW_ROWS_AROUND_ADDR 2
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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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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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}
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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)
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panic("panic_on_warn set ...\n");
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kasan_enable_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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unsigned long *entries;
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unsigned int nr_entries;
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nr_entries = stack_depot_fetch(track->stack, &entries);
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stack_trace_print(entries, nr_entries, 0);
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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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static struct page *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(struct kmem_cache *cache, void *object,
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const void *addr)
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{
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struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
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if (cache->flags & SLAB_KASAN) {
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print_track(&alloc_info->alloc_track, "Allocated");
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pr_err("\n");
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print_track(&alloc_info->free_track, "Freed");
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pr_err("\n");
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}
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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 bool __must_check tokenize_frame_descr(const char **frame_descr,
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char *token, size_t max_tok_len,
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unsigned long *value)
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{
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const char *sep = strchr(*frame_descr, ' ');
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if (sep == NULL)
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sep = *frame_descr + strlen(*frame_descr);
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if (token != NULL) {
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const size_t tok_len = sep - *frame_descr;
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if (tok_len + 1 > max_tok_len) {
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pr_err("KASAN internal error: frame description too long: %s\n",
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*frame_descr);
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return false;
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}
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/* Copy token (+ 1 byte for '\0'). */
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strlcpy(token, *frame_descr, tok_len + 1);
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}
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/* Advance frame_descr past separator. */
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*frame_descr = sep + 1;
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if (value != NULL && kstrtoul(token, 10, value)) {
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pr_err("KASAN internal error: not a valid number: %s\n", token);
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return false;
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}
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return true;
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}
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static void print_decoded_frame_descr(const char *frame_descr)
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{
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/*
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* We need to parse the following string:
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* "n alloc_1 alloc_2 ... alloc_n"
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* where alloc_i looks like
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* "offset size len name"
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* or "offset size len name:line".
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*/
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char token[64];
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unsigned long num_objects;
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if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
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&num_objects))
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return;
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pr_err("\n");
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pr_err("this frame has %lu %s:\n", num_objects,
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num_objects == 1 ? "object" : "objects");
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while (num_objects--) {
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unsigned long offset;
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unsigned long size;
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/* access offset */
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if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
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&offset))
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return;
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/* access size */
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if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
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&size))
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return;
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/* name length (unused) */
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if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
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return;
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/* object name */
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if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
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NULL))
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return;
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/* Strip line number; without filename it's not very helpful. */
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strreplace(token, ':', '\0');
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/* Finally, print object information. */
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pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
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}
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}
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static bool __must_check get_address_stack_frame_info(const void *addr,
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unsigned long *offset,
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const char **frame_descr,
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const void **frame_pc)
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{
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unsigned long aligned_addr;
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unsigned long mem_ptr;
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const u8 *shadow_bottom;
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const u8 *shadow_ptr;
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const unsigned long *frame;
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BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
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/*
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* NOTE: We currently only support printing frame information for
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* accesses to the task's own stack.
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*/
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if (!object_is_on_stack(addr))
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return false;
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aligned_addr = round_down((unsigned long)addr, sizeof(long));
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mem_ptr = round_down(aligned_addr, KASAN_SHADOW_SCALE_SIZE);
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shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
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shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
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while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
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shadow_ptr--;
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mem_ptr -= KASAN_SHADOW_SCALE_SIZE;
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}
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while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
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shadow_ptr--;
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mem_ptr -= KASAN_SHADOW_SCALE_SIZE;
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}
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if (shadow_ptr < shadow_bottom)
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return false;
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frame = (const unsigned long *)(mem_ptr + KASAN_SHADOW_SCALE_SIZE);
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if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
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pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
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frame[0]);
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return false;
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}
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*offset = (unsigned long)addr - (unsigned long)frame;
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*frame_descr = (const char *)frame[1];
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*frame_pc = (void *)frame[2];
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return true;
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}
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static void print_address_stack_frame(const void *addr)
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{
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unsigned long offset;
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const char *frame_descr;
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const void *frame_pc;
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if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
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return;
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if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
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&frame_pc))
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return;
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/*
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* get_address_stack_frame_info only returns true if the given addr is
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* on the current task's stack.
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*/
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pr_err("\n");
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pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n",
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addr, current->comm, task_pid_nr(current), offset);
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pr_err(" %pS\n", frame_pc);
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if (!frame_descr)
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return;
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print_decoded_frame_descr(frame_descr);
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}
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static void print_address_description(void *addr)
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{
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struct page *page = 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);
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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 row_is_guilty(const void *row, const void *guilty)
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{
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return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
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}
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static int shadow_pointer_offset(const void *row, const void *shadow)
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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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*/
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return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
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(shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
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}
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static void print_shadow_for_address(const void *addr)
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{
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int i;
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const void *shadow = kasan_mem_to_shadow(addr);
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const void *shadow_row;
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shadow_row = (void *)round_down((unsigned long)shadow,
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SHADOW_BYTES_PER_ROW)
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- SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
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pr_err("Memory state around the buggy address:\n");
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for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
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const void *kaddr = kasan_shadow_to_mem(shadow_row);
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char buffer[4 + (BITS_PER_LONG/8)*2];
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char shadow_buf[SHADOW_BYTES_PER_ROW];
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snprintf(buffer, sizeof(buffer),
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(i == 0) ? ">%px: " : " %px: ", kaddr);
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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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memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
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print_hex_dump(KERN_ERR, buffer,
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DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
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shadow_buf, SHADOW_BYTES_PER_ROW, 0);
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if (row_is_guilty(shadow_row, shadow))
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pr_err("%*c\n",
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shadow_pointer_offset(shadow_row, shadow),
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'^');
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shadow_row += SHADOW_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 (current->kasan_depth)
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return false;
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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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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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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(get_tag(object), reset_tag(object));
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object = reset_tag(object);
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pr_err("\n");
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print_address_description(object);
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pr_err("\n");
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print_shadow_for_address(object);
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end_report(&flags);
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}
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void __kasan_report(unsigned long addr, size_t size, bool is_write, 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 (likely(!report_enabled()))
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return;
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disable_trace_on_warning();
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tagged_addr = (void *)addr;
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untagged_addr = reset_tag(tagged_addr);
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info.access_addr = tagged_addr;
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if (addr_has_shadow(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_shadow(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_shadow(untagged_addr)) {
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print_address_description(untagged_addr);
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pr_err("\n");
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print_shadow_for_address(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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