| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * This file contains common KASAN error reporting code. |
| * |
| * Copyright (c) 2014 Samsung Electronics Co., Ltd. |
| * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com> |
| * |
| * Some code borrowed from https://github.com/xairy/kasan-prototype by |
| * Andrey Konovalov <andreyknvl@gmail.com> |
| */ |
| |
| #include <kunit/test.h> |
| #include <linux/bitops.h> |
| #include <linux/ftrace.h> |
| #include <linux/init.h> |
| #include <linux/kernel.h> |
| #include <linux/lockdep.h> |
| #include <linux/mm.h> |
| #include <linux/printk.h> |
| #include <linux/sched.h> |
| #include <linux/slab.h> |
| #include <linux/stackdepot.h> |
| #include <linux/stacktrace.h> |
| #include <linux/string.h> |
| #include <linux/types.h> |
| #include <linux/vmalloc.h> |
| #include <linux/kasan.h> |
| #include <linux/module.h> |
| #include <linux/sched/task_stack.h> |
| #include <linux/uaccess.h> |
| #include <trace/events/error_report.h> |
| |
| #include <asm/sections.h> |
| |
| #include "kasan.h" |
| #include "../slab.h" |
| |
| static unsigned long kasan_flags; |
| |
| #define KASAN_BIT_REPORTED 0 |
| #define KASAN_BIT_MULTI_SHOT 1 |
| |
| enum kasan_arg_fault { |
| KASAN_ARG_FAULT_DEFAULT, |
| KASAN_ARG_FAULT_REPORT, |
| KASAN_ARG_FAULT_PANIC, |
| KASAN_ARG_FAULT_PANIC_ON_WRITE, |
| }; |
| |
| static enum kasan_arg_fault kasan_arg_fault __ro_after_init = KASAN_ARG_FAULT_DEFAULT; |
| |
| /* kasan.fault=report/panic */ |
| static int __init early_kasan_fault(char *arg) |
| { |
| if (!arg) |
| return -EINVAL; |
| |
| if (!strcmp(arg, "report")) |
| kasan_arg_fault = KASAN_ARG_FAULT_REPORT; |
| else if (!strcmp(arg, "panic")) |
| kasan_arg_fault = KASAN_ARG_FAULT_PANIC; |
| else if (!strcmp(arg, "panic_on_write")) |
| kasan_arg_fault = KASAN_ARG_FAULT_PANIC_ON_WRITE; |
| else |
| return -EINVAL; |
| |
| return 0; |
| } |
| early_param("kasan.fault", early_kasan_fault); |
| |
| static int __init kasan_set_multi_shot(char *str) |
| { |
| set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); |
| return 1; |
| } |
| __setup("kasan_multi_shot", kasan_set_multi_shot); |
| |
| /* |
| * This function is used to check whether KASAN reports are suppressed for |
| * software KASAN modes via kasan_disable/enable_current() critical sections. |
| * |
| * This is done to avoid: |
| * 1. False-positive reports when accessing slab metadata, |
| * 2. Deadlocking when poisoned memory is accessed by the reporting code. |
| * |
| * Hardware Tag-Based KASAN instead relies on: |
| * For #1: Resetting tags via kasan_reset_tag(). |
| * For #2: Suppression of tag checks via CPU, see report_suppress_start/end(). |
| */ |
| static bool report_suppressed_sw(void) |
| { |
| #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) |
| if (current->kasan_depth) |
| return true; |
| #endif |
| return false; |
| } |
| |
| static void report_suppress_start(void) |
| { |
| #ifdef CONFIG_KASAN_HW_TAGS |
| /* |
| * Disable preemption for the duration of printing a KASAN report, as |
| * hw_suppress_tag_checks_start() disables checks on the current CPU. |
| */ |
| preempt_disable(); |
| hw_suppress_tag_checks_start(); |
| #else |
| kasan_disable_current(); |
| #endif |
| } |
| |
| static void report_suppress_stop(void) |
| { |
| #ifdef CONFIG_KASAN_HW_TAGS |
| hw_suppress_tag_checks_stop(); |
| preempt_enable(); |
| #else |
| kasan_enable_current(); |
| #endif |
| } |
| |
| /* |
| * Used to avoid reporting more than one KASAN bug unless kasan_multi_shot |
| * is enabled. Note that KASAN tests effectively enable kasan_multi_shot |
| * for their duration. |
| */ |
| static bool report_enabled(void) |
| { |
| if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) |
| return true; |
| return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags); |
| } |
| |
| #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST) |
| |
| bool kasan_save_enable_multi_shot(void) |
| { |
| return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); |
| } |
| EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot); |
| |
| void kasan_restore_multi_shot(bool enabled) |
| { |
| if (!enabled) |
| clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); |
| } |
| EXPORT_SYMBOL_GPL(kasan_restore_multi_shot); |
| |
| #endif |
| |
| #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) |
| |
| /* |
| * Whether the KASAN KUnit test suite is currently being executed. |
| * Updated in kasan_test.c. |
| */ |
| static bool kasan_kunit_executing; |
| |
| void kasan_kunit_test_suite_start(void) |
| { |
| WRITE_ONCE(kasan_kunit_executing, true); |
| } |
| EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_start); |
| |
| void kasan_kunit_test_suite_end(void) |
| { |
| WRITE_ONCE(kasan_kunit_executing, false); |
| } |
| EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_end); |
| |
| static bool kasan_kunit_test_suite_executing(void) |
| { |
| return READ_ONCE(kasan_kunit_executing); |
| } |
| |
| #else /* CONFIG_KASAN_KUNIT_TEST */ |
| |
| static inline bool kasan_kunit_test_suite_executing(void) { return false; } |
| |
| #endif /* CONFIG_KASAN_KUNIT_TEST */ |
| |
| #if IS_ENABLED(CONFIG_KUNIT) |
| |
| static void fail_non_kasan_kunit_test(void) |
| { |
| struct kunit *test; |
| |
| if (kasan_kunit_test_suite_executing()) |
| return; |
| |
| test = current->kunit_test; |
| if (test) |
| kunit_set_failure(test); |
| } |
| |
| #else /* CONFIG_KUNIT */ |
| |
| static inline void fail_non_kasan_kunit_test(void) { } |
| |
| #endif /* CONFIG_KUNIT */ |
| |
| static DEFINE_SPINLOCK(report_lock); |
| |
| static void start_report(unsigned long *flags, bool sync) |
| { |
| fail_non_kasan_kunit_test(); |
| /* Respect the /proc/sys/kernel/traceoff_on_warning interface. */ |
| disable_trace_on_warning(); |
| /* Do not allow LOCKDEP mangling KASAN reports. */ |
| lockdep_off(); |
| /* Make sure we don't end up in loop. */ |
| report_suppress_start(); |
| spin_lock_irqsave(&report_lock, *flags); |
| pr_err("==================================================================\n"); |
| } |
| |
| static void end_report(unsigned long *flags, const void *addr, bool is_write) |
| { |
| if (addr) |
| trace_error_report_end(ERROR_DETECTOR_KASAN, |
| (unsigned long)addr); |
| pr_err("==================================================================\n"); |
| spin_unlock_irqrestore(&report_lock, *flags); |
| if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) |
| check_panic_on_warn("KASAN"); |
| switch (kasan_arg_fault) { |
| case KASAN_ARG_FAULT_DEFAULT: |
| case KASAN_ARG_FAULT_REPORT: |
| break; |
| case KASAN_ARG_FAULT_PANIC: |
| panic("kasan.fault=panic set ...\n"); |
| break; |
| case KASAN_ARG_FAULT_PANIC_ON_WRITE: |
| if (is_write) |
| panic("kasan.fault=panic_on_write set ...\n"); |
| break; |
| } |
| add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); |
| lockdep_on(); |
| report_suppress_stop(); |
| } |
| |
| static void print_error_description(struct kasan_report_info *info) |
| { |
| pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip); |
| |
| if (info->type != KASAN_REPORT_ACCESS) { |
| pr_err("Free of addr %px by task %s/%d\n", |
| info->access_addr, current->comm, task_pid_nr(current)); |
| return; |
| } |
| |
| if (info->access_size) |
| pr_err("%s of size %zu at addr %px by task %s/%d\n", |
| info->is_write ? "Write" : "Read", info->access_size, |
| info->access_addr, current->comm, task_pid_nr(current)); |
| else |
| pr_err("%s at addr %px by task %s/%d\n", |
| info->is_write ? "Write" : "Read", |
| info->access_addr, current->comm, task_pid_nr(current)); |
| } |
| |
| static void print_track(struct kasan_track *track, const char *prefix) |
| { |
| #ifdef CONFIG_KASAN_EXTRA_INFO |
| u64 ts_nsec = track->timestamp; |
| unsigned long rem_usec; |
| |
| ts_nsec <<= 3; |
| rem_usec = do_div(ts_nsec, NSEC_PER_SEC) / 1000; |
| |
| pr_err("%s by task %u on cpu %d at %lu.%06lus:\n", |
| prefix, track->pid, track->cpu, |
| (unsigned long)ts_nsec, rem_usec); |
| #else |
| pr_err("%s by task %u:\n", prefix, track->pid); |
| #endif /* CONFIG_KASAN_EXTRA_INFO */ |
| if (track->stack) |
| stack_depot_print(track->stack); |
| else |
| pr_err("(stack is not available)\n"); |
| } |
| |
| static inline struct page *addr_to_page(const void *addr) |
| { |
| if (virt_addr_valid(addr)) |
| return virt_to_head_page(addr); |
| return NULL; |
| } |
| |
| static void describe_object_addr(const void *addr, struct kasan_report_info *info) |
| { |
| unsigned long access_addr = (unsigned long)addr; |
| unsigned long object_addr = (unsigned long)info->object; |
| const char *rel_type, *region_state = ""; |
| int rel_bytes; |
| |
| pr_err("The buggy address belongs to the object at %px\n" |
| " which belongs to the cache %s of size %d\n", |
| info->object, info->cache->name, info->cache->object_size); |
| |
| if (access_addr < object_addr) { |
| rel_type = "to the left"; |
| rel_bytes = object_addr - access_addr; |
| } else if (access_addr >= object_addr + info->alloc_size) { |
| rel_type = "to the right"; |
| rel_bytes = access_addr - (object_addr + info->alloc_size); |
| } else { |
| rel_type = "inside"; |
| rel_bytes = access_addr - object_addr; |
| } |
| |
| /* |
| * Tag-Based modes use the stack ring to infer the bug type, but the |
| * memory region state description is generated based on the metadata. |
| * Thus, defining the region state as below can contradict the metadata. |
| * Fixing this requires further improvements, so only infer the state |
| * for the Generic mode. |
| */ |
| if (IS_ENABLED(CONFIG_KASAN_GENERIC)) { |
| if (strcmp(info->bug_type, "slab-out-of-bounds") == 0) |
| region_state = "allocated "; |
| else if (strcmp(info->bug_type, "slab-use-after-free") == 0) |
| region_state = "freed "; |
| } |
| |
| pr_err("The buggy address is located %d bytes %s of\n" |
| " %s%zu-byte region [%px, %px)\n", |
| rel_bytes, rel_type, region_state, info->alloc_size, |
| (void *)object_addr, (void *)(object_addr + info->alloc_size)); |
| } |
| |
| static void describe_object_stacks(struct kasan_report_info *info) |
| { |
| if (info->alloc_track.stack) { |
| print_track(&info->alloc_track, "Allocated"); |
| pr_err("\n"); |
| } |
| |
| if (info->free_track.stack) { |
| print_track(&info->free_track, "Freed"); |
| pr_err("\n"); |
| } |
| |
| kasan_print_aux_stacks(info->cache, info->object); |
| } |
| |
| static void describe_object(const void *addr, struct kasan_report_info *info) |
| { |
| if (kasan_stack_collection_enabled()) |
| describe_object_stacks(info); |
| describe_object_addr(addr, info); |
| } |
| |
| static inline bool kernel_or_module_addr(const void *addr) |
| { |
| if (is_kernel((unsigned long)addr)) |
| return true; |
| if (is_module_address((unsigned long)addr)) |
| return true; |
| return false; |
| } |
| |
| static inline bool init_task_stack_addr(const void *addr) |
| { |
| return addr >= (void *)&init_thread_union.stack && |
| (addr <= (void *)&init_thread_union.stack + |
| sizeof(init_thread_union.stack)); |
| } |
| |
| static void print_address_description(void *addr, u8 tag, |
| struct kasan_report_info *info) |
| { |
| struct page *page = addr_to_page(addr); |
| |
| dump_stack_lvl(KERN_ERR); |
| pr_err("\n"); |
| |
| if (info->cache && info->object) { |
| describe_object(addr, info); |
| pr_err("\n"); |
| } |
| |
| if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) { |
| pr_err("The buggy address belongs to the variable:\n"); |
| pr_err(" %pS\n", addr); |
| pr_err("\n"); |
| } |
| |
| if (object_is_on_stack(addr)) { |
| /* |
| * Currently, KASAN supports printing frame information only |
| * for accesses to the task's own stack. |
| */ |
| kasan_print_address_stack_frame(addr); |
| pr_err("\n"); |
| } |
| |
| if (is_vmalloc_addr(addr)) { |
| struct vm_struct *va = find_vm_area(addr); |
| |
| if (va) { |
| pr_err("The buggy address belongs to the virtual mapping at\n" |
| " [%px, %px) created by:\n" |
| " %pS\n", |
| va->addr, va->addr + va->size, va->caller); |
| pr_err("\n"); |
| |
| page = vmalloc_to_page(addr); |
| } |
| } |
| |
| if (page) { |
| pr_err("The buggy address belongs to the physical page:\n"); |
| dump_page(page, "kasan: bad access detected"); |
| pr_err("\n"); |
| } |
| } |
| |
| static bool meta_row_is_guilty(const void *row, const void *addr) |
| { |
| return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW); |
| } |
| |
| static int meta_pointer_offset(const void *row, const void *addr) |
| { |
| /* |
| * Memory state around the buggy address: |
| * ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe |
| * ... |
| * |
| * The length of ">ff00ff00ff00ff00: " is |
| * 3 + (BITS_PER_LONG / 8) * 2 chars. |
| * The length of each granule metadata is 2 bytes |
| * plus 1 byte for space. |
| */ |
| return 3 + (BITS_PER_LONG / 8) * 2 + |
| (addr - row) / KASAN_GRANULE_SIZE * 3 + 1; |
| } |
| |
| static void print_memory_metadata(const void *addr) |
| { |
| int i; |
| void *row; |
| |
| row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW) |
| - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW; |
| |
| pr_err("Memory state around the buggy address:\n"); |
| |
| for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) { |
| char buffer[4 + (BITS_PER_LONG / 8) * 2]; |
| char metadata[META_BYTES_PER_ROW]; |
| |
| snprintf(buffer, sizeof(buffer), |
| (i == 0) ? ">%px: " : " %px: ", row); |
| |
| /* |
| * We should not pass a shadow pointer to generic |
| * function, because generic functions may try to |
| * access kasan mapping for the passed address. |
| */ |
| kasan_metadata_fetch_row(&metadata[0], row); |
| |
| print_hex_dump(KERN_ERR, buffer, |
| DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1, |
| metadata, META_BYTES_PER_ROW, 0); |
| |
| if (meta_row_is_guilty(row, addr)) |
| pr_err("%*c\n", meta_pointer_offset(row, addr), '^'); |
| |
| row += META_MEM_BYTES_PER_ROW; |
| } |
| } |
| |
| static void print_report(struct kasan_report_info *info) |
| { |
| void *addr = kasan_reset_tag((void *)info->access_addr); |
| u8 tag = get_tag((void *)info->access_addr); |
| |
| print_error_description(info); |
| if (addr_has_metadata(addr)) |
| kasan_print_tags(tag, info->first_bad_addr); |
| pr_err("\n"); |
| |
| if (addr_has_metadata(addr)) { |
| print_address_description(addr, tag, info); |
| print_memory_metadata(info->first_bad_addr); |
| } else { |
| dump_stack_lvl(KERN_ERR); |
| } |
| } |
| |
| static void complete_report_info(struct kasan_report_info *info) |
| { |
| void *addr = kasan_reset_tag((void *)info->access_addr); |
| struct slab *slab; |
| |
| if (info->type == KASAN_REPORT_ACCESS) |
| info->first_bad_addr = kasan_find_first_bad_addr( |
| (void *)info->access_addr, info->access_size); |
| else |
| info->first_bad_addr = addr; |
| |
| slab = kasan_addr_to_slab(addr); |
| if (slab) { |
| info->cache = slab->slab_cache; |
| info->object = nearest_obj(info->cache, slab, addr); |
| |
| /* Try to determine allocation size based on the metadata. */ |
| 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_sw(), as an invalid-free cannot be |
| * caused by accessing poisoned memory and thus should not be suppressed |
| * by kasan_disable/enable_current() critical sections. |
| * |
| * Note that for Hardware Tag-Based KASAN, kasan_report_invalid_free() |
| * is triggered by explicit tag checks and not by the ones performed by |
| * the CPU. Thus, reporting invalid-free is not suppressed as well. |
| */ |
| 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); |
| |
| /* |
| * Invalid free is considered a "write" since the allocator's metadata |
| * updates involves writes. |
| */ |
| end_report(&flags, ptr, true); |
| } |
| |
| /* |
| * 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(const void *addr, size_t size, bool is_write, |
| unsigned long ip) |
| { |
| bool ret = true; |
| unsigned long ua_flags = user_access_save(); |
| unsigned long irq_flags; |
| struct kasan_report_info info; |
| |
| if (unlikely(report_suppressed_sw()) || 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 = addr; |
| info.access_size = size; |
| info.is_write = is_write; |
| info.ip = ip; |
| |
| complete_report_info(&info); |
| |
| print_report(&info); |
| |
| end_report(&irq_flags, (void *)addr, is_write); |
| |
| 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_sw(), 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); |
| /* |
| * Conservatively set is_write=true, because no details are available. |
| * In this mode, kasan.fault=panic_on_write is like kasan.fault=panic. |
| */ |
| end_report(&flags, NULL, true); |
| } |
| #endif /* CONFIG_KASAN_HW_TAGS */ |
| |
| #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) |
| /* |
| * With compiler-based KASAN modes, accesses to bogus pointers (outside of the |
| * mapped kernel address space regions) cause faults when KASAN tries to check |
| * the shadow memory before the actual memory access. This results in cryptic |
| * GPF reports, which are hard for users to interpret. This hook helps users to |
| * figure out what the original bogus pointer was. |
| */ |
| void kasan_non_canonical_hook(unsigned long addr) |
| { |
| unsigned long orig_addr; |
| const char *bug_type; |
| |
| /* |
| * All addresses that came as a result of the memory-to-shadow mapping |
| * (even for bogus pointers) must be >= KASAN_SHADOW_OFFSET. |
| */ |
| if (addr < KASAN_SHADOW_OFFSET) |
| return; |
| |
| orig_addr = (unsigned long)kasan_shadow_to_mem((void *)addr); |
| |
| /* |
| * 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 the shadow for low or high canonical |
| * addresses, we can still be pretty sure: these shadow regions are a |
| * fairly narrow chunk of the address space. |
| * But the shadow for non-canonical addresses is a really large chunk |
| * of the address space. For this 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 if (addr_in_shadow((void *)addr)) |
| bug_type = "probably wild-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 |