| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * This file contains common generic and tag-based 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> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| * |
| */ |
| |
| #include <linux/bitops.h> |
| #include <linux/ftrace.h> |
| #include <linux/init.h> |
| #include <linux/kernel.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/kasan.h> |
| #include <linux/module.h> |
| #include <linux/sched/task_stack.h> |
| #include <trace/events/error_report.h> |
| |
| #include <asm/sections.h> |
| |
| #include "kasan.h" |
| #include "../slab.h" |
| |
| /* Shadow layout customization. */ |
| #define SHADOW_BYTES_PER_BLOCK 1 |
| #define SHADOW_BLOCKS_PER_ROW 16 |
| #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK) |
| #define SHADOW_ROWS_AROUND_ADDR 2 |
| |
| static unsigned long kasan_flags; |
| |
| #define KASAN_BIT_REPORTED 0 |
| #define KASAN_BIT_MULTI_SHOT 1 |
| |
| 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); |
| |
| 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); |
| |
| static void print_error_description(struct kasan_access_info *info) |
| { |
| pr_err("BUG: KASAN: %s in %pS\n", |
| get_bug_type(info), (void *)info->ip); |
| 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)); |
| } |
| |
| static DEFINE_SPINLOCK(report_lock); |
| |
| static void start_report(unsigned long *flags) |
| { |
| /* |
| * Make sure we don't end up in loop. |
| */ |
| kasan_disable_current(); |
| spin_lock_irqsave(&report_lock, *flags); |
| pr_err("==================================================================\n"); |
| } |
| |
| static void end_report(unsigned long *flags, unsigned long addr) |
| { |
| trace_error_report_end(ERROR_DETECTOR_KASAN, addr); |
| pr_err("==================================================================\n"); |
| add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); |
| spin_unlock_irqrestore(&report_lock, *flags); |
| if (panic_on_warn) { |
| /* |
| * This thread may hit another WARN() in the panic path. |
| * Resetting this prevents additional WARN() from panicking the |
| * system on this thread. Other threads are blocked by the |
| * panic_mutex in panic(). |
| */ |
| panic_on_warn = 0; |
| panic("panic_on_warn set ...\n"); |
| } |
| kasan_enable_current(); |
| } |
| |
| static void print_track(struct kasan_track *track, const char *prefix) |
| { |
| pr_err("%s by task %u:\n", prefix, track->pid); |
| if (track->stack) { |
| unsigned long *entries; |
| unsigned int nr_entries; |
| |
| nr_entries = stack_depot_fetch(track->stack, &entries); |
| stack_trace_print(entries, nr_entries, 0); |
| } else { |
| pr_err("(stack is not available)\n"); |
| } |
| } |
| |
| struct page *kasan_addr_to_page(const void *addr) |
| { |
| if ((addr >= (void *)PAGE_OFFSET) && |
| (addr < high_memory)) |
| return virt_to_head_page(addr); |
| return NULL; |
| } |
| |
| static void describe_object_addr(struct kmem_cache *cache, void *object, |
| const void *addr) |
| { |
| unsigned long access_addr = (unsigned long)addr; |
| unsigned long object_addr = (unsigned long)object; |
| const char *rel_type; |
| 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", |
| object, cache->name, cache->object_size); |
| |
| if (!addr) |
| return; |
| |
| if (access_addr < object_addr) { |
| rel_type = "to the left"; |
| rel_bytes = object_addr - access_addr; |
| } else if (access_addr >= object_addr + cache->object_size) { |
| rel_type = "to the right"; |
| rel_bytes = access_addr - (object_addr + cache->object_size); |
| } else { |
| rel_type = "inside"; |
| rel_bytes = access_addr - object_addr; |
| } |
| |
| pr_err("The buggy address is located %d bytes %s of\n" |
| " %d-byte region [%px, %px)\n", |
| rel_bytes, rel_type, cache->object_size, (void *)object_addr, |
| (void *)(object_addr + cache->object_size)); |
| } |
| |
| static struct kasan_track *kasan_get_free_track(struct kmem_cache *cache, |
| void *object, u8 tag) |
| { |
| struct kasan_alloc_meta *alloc_meta; |
| int i = 0; |
| |
| alloc_meta = get_alloc_info(cache, object); |
| |
| #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY |
| for (i = 0; i < KASAN_NR_FREE_STACKS; i++) { |
| if (alloc_meta->free_pointer_tag[i] == tag) |
| break; |
| } |
| if (i == KASAN_NR_FREE_STACKS) |
| i = alloc_meta->free_track_idx; |
| #endif |
| |
| return &alloc_meta->free_track[i]; |
| } |
| |
| static void describe_object(struct kmem_cache *cache, void *object, |
| const void *addr, u8 tag) |
| { |
| struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object); |
| |
| if (cache->flags & SLAB_KASAN) { |
| struct kasan_track *free_track; |
| |
| print_track(&alloc_info->alloc_track, "Allocated"); |
| pr_err("\n"); |
| free_track = kasan_get_free_track(cache, object, tag); |
| print_track(free_track, "Freed"); |
| pr_err("\n"); |
| } |
| |
| describe_object_addr(cache, object, addr); |
| } |
| |
| static inline bool kernel_or_module_addr(const void *addr) |
| { |
| if (addr >= (void *)_stext && addr < (void *)_end) |
| 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 bool __must_check tokenize_frame_descr(const char **frame_descr, |
| char *token, size_t max_tok_len, |
| unsigned long *value) |
| { |
| const char *sep = strchr(*frame_descr, ' '); |
| |
| if (sep == NULL) |
| sep = *frame_descr + strlen(*frame_descr); |
| |
| if (token != NULL) { |
| const size_t tok_len = sep - *frame_descr; |
| |
| if (tok_len + 1 > max_tok_len) { |
| pr_err("KASAN internal error: frame description too long: %s\n", |
| *frame_descr); |
| return false; |
| } |
| |
| /* Copy token (+ 1 byte for '\0'). */ |
| strlcpy(token, *frame_descr, tok_len + 1); |
| } |
| |
| /* Advance frame_descr past separator. */ |
| *frame_descr = sep + 1; |
| |
| if (value != NULL && kstrtoul(token, 10, value)) { |
| pr_err("KASAN internal error: not a valid number: %s\n", token); |
| return false; |
| } |
| |
| return true; |
| } |
| |
| static void print_decoded_frame_descr(const char *frame_descr) |
| { |
| /* |
| * We need to parse the following string: |
| * "n alloc_1 alloc_2 ... alloc_n" |
| * where alloc_i looks like |
| * "offset size len name" |
| * or "offset size len name:line". |
| */ |
| |
| char token[64]; |
| unsigned long num_objects; |
| |
| if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), |
| &num_objects)) |
| return; |
| |
| pr_err("\n"); |
| pr_err("this frame has %lu %s:\n", num_objects, |
| num_objects == 1 ? "object" : "objects"); |
| |
| while (num_objects--) { |
| unsigned long offset; |
| unsigned long size; |
| |
| /* access offset */ |
| if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), |
| &offset)) |
| return; |
| /* access size */ |
| if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), |
| &size)) |
| return; |
| /* name length (unused) */ |
| if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL)) |
| return; |
| /* object name */ |
| if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), |
| NULL)) |
| return; |
| |
| /* Strip line number; without filename it's not very helpful. */ |
| strreplace(token, ':', '\0'); |
| |
| /* Finally, print object information. */ |
| pr_err(" [%lu, %lu) '%s'", offset, offset + size, token); |
| } |
| } |
| |
| static bool __must_check get_address_stack_frame_info(const void *addr, |
| unsigned long *offset, |
| const char **frame_descr, |
| const void **frame_pc) |
| { |
| unsigned long aligned_addr; |
| unsigned long mem_ptr; |
| const u8 *shadow_bottom; |
| const u8 *shadow_ptr; |
| const unsigned long *frame; |
| |
| BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP)); |
| |
| /* |
| * NOTE: We currently only support printing frame information for |
| * accesses to the task's own stack. |
| */ |
| if (!object_is_on_stack(addr)) |
| return false; |
| |
| aligned_addr = round_down((unsigned long)addr, sizeof(long)); |
| mem_ptr = round_down(aligned_addr, KASAN_SHADOW_SCALE_SIZE); |
| shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr); |
| shadow_bottom = kasan_mem_to_shadow(end_of_stack(current)); |
| |
| while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) { |
| shadow_ptr--; |
| mem_ptr -= KASAN_SHADOW_SCALE_SIZE; |
| } |
| |
| while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) { |
| shadow_ptr--; |
| mem_ptr -= KASAN_SHADOW_SCALE_SIZE; |
| } |
| |
| if (shadow_ptr < shadow_bottom) |
| return false; |
| |
| frame = (const unsigned long *)(mem_ptr + KASAN_SHADOW_SCALE_SIZE); |
| if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) { |
| pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n", |
| frame[0]); |
| return false; |
| } |
| |
| *offset = (unsigned long)addr - (unsigned long)frame; |
| *frame_descr = (const char *)frame[1]; |
| *frame_pc = (void *)frame[2]; |
| |
| return true; |
| } |
| |
| static void print_address_stack_frame(const void *addr) |
| { |
| unsigned long offset; |
| const char *frame_descr; |
| const void *frame_pc; |
| |
| if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) |
| return; |
| |
| if (!get_address_stack_frame_info(addr, &offset, &frame_descr, |
| &frame_pc)) |
| return; |
| |
| /* |
| * get_address_stack_frame_info only returns true if the given addr is |
| * on the current task's stack. |
| */ |
| pr_err("\n"); |
| pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n", |
| addr, current->comm, task_pid_nr(current), offset); |
| pr_err(" %pS\n", frame_pc); |
| |
| if (!frame_descr) |
| return; |
| |
| print_decoded_frame_descr(frame_descr); |
| } |
| |
| static void print_address_description(void *addr, u8 tag) |
| { |
| struct page *page = kasan_addr_to_page(addr); |
| |
| dump_stack(); |
| pr_err("\n"); |
| |
| if (page && PageSlab(page)) { |
| struct kmem_cache *cache = page->slab_cache; |
| void *object = nearest_obj(cache, page, addr); |
| |
| describe_object(cache, object, addr, tag); |
| } |
| |
| 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); |
| } |
| |
| if (page) { |
| pr_err("The buggy address belongs to the page:\n"); |
| dump_page(page, "kasan: bad access detected"); |
| } |
| |
| print_address_stack_frame(addr); |
| } |
| |
| static bool row_is_guilty(const void *row, const void *guilty) |
| { |
| return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW); |
| } |
| |
| static int shadow_pointer_offset(const void *row, const void *shadow) |
| { |
| /* The length of ">ff00ff00ff00ff00: " is |
| * 3 + (BITS_PER_LONG/8)*2 chars. |
| */ |
| return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 + |
| (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1; |
| } |
| |
| static void print_shadow_for_address(const void *addr) |
| { |
| int i; |
| const void *shadow = kasan_mem_to_shadow(addr); |
| const void *shadow_row; |
| |
| shadow_row = (void *)round_down((unsigned long)shadow, |
| SHADOW_BYTES_PER_ROW) |
| - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW; |
| |
| pr_err("Memory state around the buggy address:\n"); |
| |
| for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) { |
| const void *kaddr = kasan_shadow_to_mem(shadow_row); |
| char buffer[4 + (BITS_PER_LONG/8)*2]; |
| char shadow_buf[SHADOW_BYTES_PER_ROW]; |
| |
| snprintf(buffer, sizeof(buffer), |
| (i == 0) ? ">%px: " : " %px: ", kaddr); |
| /* |
| * We should not pass a shadow pointer to generic |
| * function, because generic functions may try to |
| * access kasan mapping for the passed address. |
| */ |
| memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW); |
| print_hex_dump(KERN_ERR, buffer, |
| DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1, |
| shadow_buf, SHADOW_BYTES_PER_ROW, 0); |
| |
| if (row_is_guilty(shadow_row, shadow)) |
| pr_err("%*c\n", |
| shadow_pointer_offset(shadow_row, shadow), |
| '^'); |
| |
| shadow_row += SHADOW_BYTES_PER_ROW; |
| } |
| } |
| |
| static bool report_enabled(void) |
| { |
| if (current->kasan_depth) |
| return false; |
| if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) |
| return true; |
| return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags); |
| } |
| |
| void kasan_report_invalid_free(void *object, unsigned long ip) |
| { |
| unsigned long flags; |
| u8 tag = get_tag(object); |
| |
| object = reset_tag(object); |
| start_report(&flags); |
| pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip); |
| print_tags(tag, object); |
| pr_err("\n"); |
| print_address_description(object, tag); |
| pr_err("\n"); |
| print_shadow_for_address(object); |
| end_report(&flags, (unsigned long)object); |
| } |
| |
| void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) |
| { |
| struct kasan_access_info info; |
| void *tagged_addr; |
| void *untagged_addr; |
| unsigned long flags; |
| |
| if (likely(!report_enabled())) |
| return; |
| |
| disable_trace_on_warning(); |
| |
| tagged_addr = (void *)addr; |
| untagged_addr = reset_tag(tagged_addr); |
| |
| info.access_addr = tagged_addr; |
| if (addr_has_shadow(untagged_addr)) |
| info.first_bad_addr = find_first_bad_addr(tagged_addr, size); |
| else |
| info.first_bad_addr = untagged_addr; |
| info.access_size = size; |
| info.is_write = is_write; |
| info.ip = ip; |
| |
| start_report(&flags); |
| |
| print_error_description(&info); |
| if (addr_has_shadow(untagged_addr)) |
| print_tags(get_tag(tagged_addr), info.first_bad_addr); |
| pr_err("\n"); |
| |
| if (addr_has_shadow(untagged_addr)) { |
| print_address_description(untagged_addr, get_tag(tagged_addr)); |
| pr_err("\n"); |
| print_shadow_for_address(info.first_bad_addr); |
| } else { |
| dump_stack(); |
| } |
| |
| end_report(&flags, addr); |
| } |