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8f17febb34
Make KASAN scan metadata to infer the requested allocation size instead of printing cache->object_size. This patch fixes confusing slab-out-of-bounds reports as reported in: https://bugzilla.kernel.org/show_bug.cgi?id=216457 As an example of the confusing behavior, the report below hints that the allocation size was 192, while the kernel actually called kmalloc(184): ================================================================== BUG: KASAN: slab-out-of-bounds in _find_next_bit+0x143/0x160 lib/find_bit.c:109 Read of size 8 at addr ffff8880175766b8 by task kworker/1:1/26 ... The buggy address belongs to the object at ffff888017576600 which belongs to the cache kmalloc-192 of size 192 The buggy address is located 184 bytes inside of 192-byte region [ffff888017576600, ffff8880175766c0) ... Memory state around the buggy address: ffff888017576580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff888017576600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff888017576680: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc ^ ffff888017576700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888017576780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== With this patch, the report shows: ================================================================== ... The buggy address belongs to the object at ffff888017576600 which belongs to the cache kmalloc-192 of size 192 The buggy address is located 0 bytes to the right of allocated 184-byte region [ffff888017576600, ffff8880175766b8) ... ================================================================== Also report slab use-after-free bugs as "slab-use-after-free" and print "freed" instead of "allocated" in the report when describing the accessed memory region. Also improve the metadata-related comment in kasan_find_first_bad_addr and use addr_has_metadata across KASAN code instead of open-coding KASAN_SHADOW_START checks. [akpm@linux-foundation.org: fix printk warning] Link: https://bugzilla.kernel.org/show_bug.cgi?id=216457 Link: https://lkml.kernel.org/r/20230129021437.18812-1-Kuan-Ying.Lee@mediatek.com Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> Co-developed-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Chinwen Chang <chinwen.chang@mediatek.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Matthias Brugger <matthias.bgg@gmail.com> Cc: Qun-Wei Lin <qun-wei.lin@mediatek.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
606 lines
16 KiB
C
606 lines
16 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 <kunit/test.h>
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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 "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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/*
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* Whether the KASAN KUnit test suite is currently being executed.
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* Updated in kasan_test.c.
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*/
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static bool kasan_kunit_executing;
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void kasan_kunit_test_suite_start(void)
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{
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WRITE_ONCE(kasan_kunit_executing, true);
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}
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EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_start);
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void kasan_kunit_test_suite_end(void)
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{
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WRITE_ONCE(kasan_kunit_executing, false);
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}
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EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_end);
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static bool kasan_kunit_test_suite_executing(void)
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{
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return READ_ONCE(kasan_kunit_executing);
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}
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#else /* CONFIG_KASAN_KUNIT_TEST */
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static inline bool kasan_kunit_test_suite_executing(void) { return false; }
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#endif /* CONFIG_KASAN_KUNIT_TEST */
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#if IS_ENABLED(CONFIG_KUNIT)
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static void fail_non_kasan_kunit_test(void)
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{
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struct kunit *test;
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if (kasan_kunit_test_suite_executing())
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return;
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test = current->kunit_test;
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if (test)
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kunit_set_failure(test);
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}
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#else /* CONFIG_KUNIT */
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static inline void fail_non_kasan_kunit_test(void) { }
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#endif /* CONFIG_KUNIT */
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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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fail_non_kasan_kunit_test();
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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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/* 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 (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
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check_panic_on_warn("KASAN");
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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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pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip);
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if (info->type != KASAN_REPORT_ACCESS) {
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pr_err("Free of addr %px by task %s/%d\n",
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info->access_addr, current->comm, task_pid_nr(current));
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return;
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}
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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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static inline struct page *addr_to_page(const void *addr)
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{
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if (virt_addr_valid(addr))
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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(const void *addr, struct kasan_report_info *info)
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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)info->object;
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const char *rel_type, *region_state = "";
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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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info->object, info->cache->name, info->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 + info->alloc_size) {
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rel_type = "to the right";
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rel_bytes = access_addr - (object_addr + info->alloc_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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/*
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* Tag-Based modes use the stack ring to infer the bug type, but the
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* memory region state description is generated based on the metadata.
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* Thus, defining the region state as below can contradict the metadata.
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* Fixing this requires further improvements, so only infer the state
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* for the Generic mode.
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*/
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if (IS_ENABLED(CONFIG_KASAN_GENERIC)) {
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if (strcmp(info->bug_type, "slab-out-of-bounds") == 0)
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region_state = "allocated ";
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else if (strcmp(info->bug_type, "slab-use-after-free") == 0)
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region_state = "freed ";
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}
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pr_err("The buggy address is located %d bytes %s of\n"
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" %s%zu-byte region [%px, %px)\n",
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rel_bytes, rel_type, region_state, info->alloc_size,
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(void *)object_addr, (void *)(object_addr + info->alloc_size));
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}
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static void describe_object_stacks(struct kasan_report_info *info)
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{
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if (info->alloc_track.stack) {
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print_track(&info->alloc_track, "Allocated");
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pr_err("\n");
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}
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if (info->free_track.stack) {
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print_track(&info->free_track, "Freed");
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pr_err("\n");
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}
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kasan_print_aux_stacks(info->cache, info->object);
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}
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static void describe_object(const void *addr, struct kasan_report_info *info)
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{
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if (kasan_stack_collection_enabled())
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describe_object_stacks(info);
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describe_object_addr(addr, info);
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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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struct kasan_report_info *info)
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{
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struct page *page = 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 (info->cache && info->object) {
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describe_object(addr, info);
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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 *addr = kasan_reset_tag(info->access_addr);
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u8 tag = get_tag(info->access_addr);
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print_error_description(info);
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if (addr_has_metadata(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(addr)) {
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print_address_description(addr, tag, info);
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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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static void complete_report_info(struct kasan_report_info *info)
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{
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void *addr = kasan_reset_tag(info->access_addr);
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struct slab *slab;
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if (info->type == KASAN_REPORT_ACCESS)
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info->first_bad_addr = kasan_find_first_bad_addr(
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info->access_addr, info->access_size);
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else
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info->first_bad_addr = addr;
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slab = kasan_addr_to_slab(addr);
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if (slab) {
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info->cache = slab->slab_cache;
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info->object = nearest_obj(info->cache, slab, addr);
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/* Try to determine allocation size based on the metadata. */
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info->alloc_size = kasan_get_alloc_size(info->object, info->cache);
|
|
/* Fallback to the object size if failed. */
|
|
if (!info->alloc_size)
|
|
info->alloc_size = info->cache->object_size;
|
|
} else
|
|
info->cache = info->object = NULL;
|
|
|
|
switch (info->type) {
|
|
case KASAN_REPORT_INVALID_FREE:
|
|
info->bug_type = "invalid-free";
|
|
break;
|
|
case KASAN_REPORT_DOUBLE_FREE:
|
|
info->bug_type = "double-free";
|
|
break;
|
|
default:
|
|
/* bug_type filled in by kasan_complete_mode_report_info. */
|
|
break;
|
|
}
|
|
|
|
/* Fill in mode-specific report info fields. */
|
|
kasan_complete_mode_report_info(info);
|
|
}
|
|
|
|
void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type)
|
|
{
|
|
unsigned long flags;
|
|
struct kasan_report_info info;
|
|
|
|
/*
|
|
* Do not check report_suppressed(), as an invalid-free cannot be
|
|
* caused by accessing slab metadata and thus should not be
|
|
* suppressed by kasan_disable/enable_current() critical sections.
|
|
*/
|
|
if (unlikely(!report_enabled()))
|
|
return;
|
|
|
|
start_report(&flags, true);
|
|
|
|
memset(&info, 0, sizeof(info));
|
|
info.type = type;
|
|
info.access_addr = ptr;
|
|
info.access_size = 0;
|
|
info.is_write = false;
|
|
info.ip = ip;
|
|
|
|
complete_report_info(&info);
|
|
|
|
print_report(&info);
|
|
|
|
end_report(&flags, ptr);
|
|
}
|
|
|
|
/*
|
|
* kasan_report() is the only reporting function that uses
|
|
* user_access_save/restore(): kasan_report_invalid_free() cannot be called
|
|
* from a UACCESS region, and kasan_report_async() is not used on x86.
|
|
*/
|
|
bool kasan_report(unsigned long addr, size_t size, bool is_write,
|
|
unsigned long ip)
|
|
{
|
|
bool ret = true;
|
|
void *ptr = (void *)addr;
|
|
unsigned long ua_flags = user_access_save();
|
|
unsigned long irq_flags;
|
|
struct kasan_report_info info;
|
|
|
|
if (unlikely(report_suppressed()) || unlikely(!report_enabled())) {
|
|
ret = false;
|
|
goto out;
|
|
}
|
|
|
|
start_report(&irq_flags, true);
|
|
|
|
memset(&info, 0, sizeof(info));
|
|
info.type = KASAN_REPORT_ACCESS;
|
|
info.access_addr = ptr;
|
|
info.access_size = size;
|
|
info.is_write = is_write;
|
|
info.ip = ip;
|
|
|
|
complete_report_info(&info);
|
|
|
|
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
|