mm/kasan/report.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * This file contains common generic and tag-based KASAN error reporting code.
   4  *
   5  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
   6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   7  *
   8  * Some code borrowed from https://github.com/xairy/kasan-prototype by
   9  *        Andrey Konovalov <andreyknvl@gmail.com>
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License version 2 as
  13  * published by the Free Software Foundation.
  14  *
  15  */
  16
  17 #include <linux/bitops.h>
  18 #include <linux/ftrace.h>
  19 #include <linux/init.h>
  20 #include <linux/kernel.h>
  21 #include <linux/mm.h>
  22 #include <linux/printk.h>
  23 #include <linux/sched.h>
  24 #include <linux/slab.h>
  25 #include <linux/stackdepot.h>
  26 #include <linux/stacktrace.h>
  27 #include <linux/string.h>
  28 #include <linux/types.h>
  29 #include <linux/kasan.h>
  30 #include <linux/module.h>
  31
  32 #include <asm/sections.h>
  33
  34 #include "kasan.h"
  35 #include "../slab.h"
  36
  37 /* Shadow layout customization. */
  38 #define SHADOW_BYTES_PER_BLOCK 1
  39 #define SHADOW_BLOCKS_PER_ROW 16
  40 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
  41 #define SHADOW_ROWS_AROUND_ADDR 2
  42
  43 static unsigned long kasan_flags;
  44
  45 #define KASAN_BIT_REPORTED      0
  46 #define KASAN_BIT_MULTI_SHOT    1
  47
  48 bool kasan_save_enable_multi_shot(void)
  49 {
  50         return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  51 }
  52 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
  53
  54 void kasan_restore_multi_shot(bool enabled)
  55 {
  56         if (!enabled)
  57                 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  58 }
  59 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
  60
  61 static int __init kasan_set_multi_shot(char *str)
  62 {
  63         set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  64         return 1;
  65 }
  66 __setup("kasan_multi_shot", kasan_set_multi_shot);
  67
  68 static void print_error_description(struct kasan_access_info *info)
  69 {
  70         pr_err("BUG: KASAN: %s in %pS\n",
  71                 get_bug_type(info), (void *)info->ip);
  72         pr_err("%s of size %zu at addr %px by task %s/%d\n",
  73                 info->is_write ? "Write" : "Read", info->access_size,
  74                 info->access_addr, current->comm, task_pid_nr(current));
  75 }
  76
  77 static DEFINE_SPINLOCK(report_lock);
  78
  79 static void start_report(unsigned long *flags)
  80 {
  81         /*
  82          * Make sure we don't end up in loop.
  83          */
  84         kasan_disable_current();
  85         spin_lock_irqsave(&report_lock, *flags);
  86         pr_err("==================================================================\n");
  87 }
  88
  89 static void end_report(unsigned long *flags)
  90 {
  91         pr_err("==================================================================\n");
  92         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
  93         spin_unlock_irqrestore(&report_lock, *flags);
  94         if (panic_on_warn)
  95                 panic("panic_on_warn set ...\n");
  96         kasan_enable_current();
  97 }
  98
  99 static void print_track(struct kasan_track *track, const char *prefix)
 100 {
 101         pr_err("%s by task %u:\n", prefix, track->pid);
 102         if (track->stack) {
 103                 unsigned long *entries;
 104                 unsigned int nr_entries;
 105
 106                 nr_entries = stack_depot_fetch(track->stack, &entries);
 107                 stack_trace_print(entries, nr_entries, 0);
 108         } else {
 109                 pr_err("(stack is not available)\n");
 110         }
 111 }
 112
 113 static struct page *addr_to_page(const void *addr)
 114 {
 115         if ((addr >= (void *)PAGE_OFFSET) &&
 116                         (addr < high_memory))
 117                 return virt_to_head_page(addr);
 118         return NULL;
 119 }
 120
 121 static void describe_object_addr(struct kmem_cache *cache, void *object,
 122                                 const void *addr)
 123 {
 124         unsigned long access_addr = (unsigned long)addr;
 125         unsigned long object_addr = (unsigned long)object;
 126         const char *rel_type;
 127         int rel_bytes;
 128
 129         pr_err("The buggy address belongs to the object at %px\n"
 130                " which belongs to the cache %s of size %d\n",
 131                 object, cache->name, cache->object_size);
 132
 133         if (!addr)
 134                 return;
 135
 136         if (access_addr < object_addr) {
 137                 rel_type = "to the left";
 138                 rel_bytes = object_addr - access_addr;
 139         } else if (access_addr >= object_addr + cache->object_size) {
 140                 rel_type = "to the right";
 141                 rel_bytes = access_addr - (object_addr + cache->object_size);
 142         } else {
 143                 rel_type = "inside";
 144                 rel_bytes = access_addr - object_addr;
 145         }
 146
 147         pr_err("The buggy address is located %d bytes %s of\n"
 148                " %d-byte region [%px, %px)\n",
 149                 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
 150                 (void *)(object_addr + cache->object_size));
 151 }
 152
 153 static void describe_object(struct kmem_cache *cache, void *object,
 154                                 const void *addr)
 155 {
 156         struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
 157
 158         if (cache->flags & SLAB_KASAN) {
 159                 print_track(&alloc_info->alloc_track, "Allocated");
 160                 pr_err("\n");
 161                 print_track(&alloc_info->free_track, "Freed");
 162                 pr_err("\n");
 163         }
 164
 165         describe_object_addr(cache, object, addr);
 166 }
 167
 168 static inline bool kernel_or_module_addr(const void *addr)
 169 {
 170         if (addr >= (void *)_stext && addr < (void *)_end)
 171                 return true;
 172         if (is_module_address((unsigned long)addr))
 173                 return true;
 174         return false;
 175 }
 176
 177 static inline bool init_task_stack_addr(const void *addr)
 178 {
 179         return addr >= (void *)&init_thread_union.stack &&
 180                 (addr <= (void *)&init_thread_union.stack +
 181                         sizeof(init_thread_union.stack));
 182 }
 183
 184 static void print_address_description(void *addr)
 185 {
 186         struct page *page = addr_to_page(addr);
 187
 188         dump_stack();
 189         pr_err("\n");
 190
 191         if (page && PageSlab(page)) {
 192                 struct kmem_cache *cache = page->slab_cache;
 193                 void *object = nearest_obj(cache, page, addr);
 194
 195                 describe_object(cache, object, addr);
 196         }
 197
 198         if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
 199                 pr_err("The buggy address belongs to the variable:\n");
 200                 pr_err(" %pS\n", addr);
 201         }
 202
 203         if (page) {
 204                 pr_err("The buggy address belongs to the page:\n");
 205                 dump_page(page, "kasan: bad access detected");
 206         }
 207 }
 208
 209 static bool row_is_guilty(const void *row, const void *guilty)
 210 {
 211         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
 212 }
 213
 214 static int shadow_pointer_offset(const void *row, const void *shadow)
 215 {
 216         /* The length of ">ff00ff00ff00ff00: " is
 217          *    3 + (BITS_PER_LONG/8)*2 chars.
 218          */
 219         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 220                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
 221 }
 222
 223 static void print_shadow_for_address(const void *addr)
 224 {
 225         int i;
 226         const void *shadow = kasan_mem_to_shadow(addr);
 227         const void *shadow_row;
 228
 229         shadow_row = (void *)round_down((unsigned long)shadow,
 230                                         SHADOW_BYTES_PER_ROW)
 231                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
 232
 233         pr_err("Memory state around the buggy address:\n");
 234
 235         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 236                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 237                 char buffer[4 + (BITS_PER_LONG/8)*2];
 238                 char shadow_buf[SHADOW_BYTES_PER_ROW];
 239
 240                 snprintf(buffer, sizeof(buffer),
 241                         (i == 0) ? ">%px: " : " %px: ", kaddr);
 242                 /*
 243                  * We should not pass a shadow pointer to generic
 244                  * function, because generic functions may try to
 245                  * access kasan mapping for the passed address.
 246                  */
 247                 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
 248                 print_hex_dump(KERN_ERR, buffer,
 249                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 250                         shadow_buf, SHADOW_BYTES_PER_ROW, 0);
 251
 252                 if (row_is_guilty(shadow_row, shadow))
 253                         pr_err("%*c\n",
 254                                 shadow_pointer_offset(shadow_row, shadow),
 255                                 '^');
 256
 257                 shadow_row += SHADOW_BYTES_PER_ROW;
 258         }
 259 }
 260
 261 static bool report_enabled(void)
 262 {
 263         if (current->kasan_depth)
 264                 return false;
 265         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 266                 return true;
 267         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 268 }
 269
 270 void kasan_report_invalid_free(void *object, unsigned long ip)
 271 {
 272         unsigned long flags;
 273
 274         start_report(&flags);
 275         pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
 276         print_tags(get_tag(object), reset_tag(object));
 277         object = reset_tag(object);
 278         pr_err("\n");
 279         print_address_description(object);
 280         pr_err("\n");
 281         print_shadow_for_address(object);
 282         end_report(&flags);
 283 }
 284
 285 void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
 286 {
 287         struct kasan_access_info info;
 288         void *tagged_addr;
 289         void *untagged_addr;
 290         unsigned long flags;
 291
 292         if (likely(!report_enabled()))
 293                 return;
 294
 295         disable_trace_on_warning();
 296
 297         tagged_addr = (void *)addr;
 298         untagged_addr = reset_tag(tagged_addr);
 299
 300         info.access_addr = tagged_addr;
 301         if (addr_has_shadow(untagged_addr))
 302                 info.first_bad_addr = find_first_bad_addr(tagged_addr, size);
 303         else
 304                 info.first_bad_addr = untagged_addr;
 305         info.access_size = size;
 306         info.is_write = is_write;
 307         info.ip = ip;
 308
 309         start_report(&flags);
 310
 311         print_error_description(&info);
 312         if (addr_has_shadow(untagged_addr))
 313                 print_tags(get_tag(tagged_addr), info.first_bad_addr);
 314         pr_err("\n");
 315
 316         if (addr_has_shadow(untagged_addr)) {
 317                 print_address_description(untagged_addr);
 318                 pr_err("\n");
 319                 print_shadow_for_address(info.first_bad_addr);
 320         } else {
 321                 dump_stack();
 322         }
 323
 324         end_report(&flags);
 325 }