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                 struct stack_trace trace;
 104
 105                 depot_fetch_stack(track->stack, &trace);
 106                 print_stack_trace(&trace, 0);
 107         } else {
 108                 pr_err("(stack is not available)\n");
 109         }
 110 }
 111
 112 static struct page *addr_to_page(const void *addr)
 113 {
 114         if ((addr >= (void *)PAGE_OFFSET) &&
 115                         (addr < high_memory))
 116                 return virt_to_head_page(addr);
 117         return NULL;
 118 }
 119
 120 static void describe_object_addr(struct kmem_cache *cache, void *object,
 121                                 const void *addr)
 122 {
 123         unsigned long access_addr = (unsigned long)addr;
 124         unsigned long object_addr = (unsigned long)object;
 125         const char *rel_type;
 126         int rel_bytes;
 127
 128         pr_err("The buggy address belongs to the object at %px\n"
 129                " which belongs to the cache %s of size %d\n",
 130                 object, cache->name, cache->object_size);
 131
 132         if (!addr)
 133                 return;
 134
 135         if (access_addr < object_addr) {
 136                 rel_type = "to the left";
 137                 rel_bytes = object_addr - access_addr;
 138         } else if (access_addr >= object_addr + cache->object_size) {
 139                 rel_type = "to the right";
 140                 rel_bytes = access_addr - (object_addr + cache->object_size);
 141         } else {
 142                 rel_type = "inside";
 143                 rel_bytes = access_addr - object_addr;
 144         }
 145
 146         pr_err("The buggy address is located %d bytes %s of\n"
 147                " %d-byte region [%px, %px)\n",
 148                 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
 149                 (void *)(object_addr + cache->object_size));
 150 }
 151
 152 static void describe_object(struct kmem_cache *cache, void *object,
 153                                 const void *addr)
 154 {
 155         struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
 156
 157         if (cache->flags & SLAB_KASAN) {
 158                 print_track(&alloc_info->alloc_track, "Allocated");
 159                 pr_err("\n");
 160                 print_track(&alloc_info->free_track, "Freed");
 161                 pr_err("\n");
 162         }
 163
 164         describe_object_addr(cache, object, addr);
 165 }
 166
 167 static inline bool kernel_or_module_addr(const void *addr)
 168 {
 169         if (addr >= (void *)_stext && addr < (void *)_end)
 170                 return true;
 171         if (is_module_address((unsigned long)addr))
 172                 return true;
 173         return false;
 174 }
 175
 176 static inline bool init_task_stack_addr(const void *addr)
 177 {
 178         return addr >= (void *)&init_thread_union.stack &&
 179                 (addr <= (void *)&init_thread_union.stack +
 180                         sizeof(init_thread_union.stack));
 181 }
 182
 183 static void print_address_description(void *addr)
 184 {
 185         struct page *page = addr_to_page(addr);
 186
 187         dump_stack();
 188         pr_err("\n");
 189
 190         if (page && PageSlab(page)) {
 191                 struct kmem_cache *cache = page->slab_cache;
 192                 void *object = nearest_obj(cache, page, addr);
 193
 194                 describe_object(cache, object, addr);
 195         }
 196
 197         if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
 198                 pr_err("The buggy address belongs to the variable:\n");
 199                 pr_err(" %pS\n", addr);
 200         }
 201
 202         if (page) {
 203                 pr_err("The buggy address belongs to the page:\n");
 204                 dump_page(page, "kasan: bad access detected");
 205         }
 206 }
 207
 208 static bool row_is_guilty(const void *row, const void *guilty)
 209 {
 210         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
 211 }
 212
 213 static int shadow_pointer_offset(const void *row, const void *shadow)
 214 {
 215         /* The length of ">ff00ff00ff00ff00: " is
 216          *    3 + (BITS_PER_LONG/8)*2 chars.
 217          */
 218         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 219                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
 220 }
 221
 222 static void print_shadow_for_address(const void *addr)
 223 {
 224         int i;
 225         const void *shadow = kasan_mem_to_shadow(addr);
 226         const void *shadow_row;
 227
 228         shadow_row = (void *)round_down((unsigned long)shadow,
 229                                         SHADOW_BYTES_PER_ROW)
 230                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
 231
 232         pr_err("Memory state around the buggy address:\n");
 233
 234         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 235                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 236                 char buffer[4 + (BITS_PER_LONG/8)*2];
 237                 char shadow_buf[SHADOW_BYTES_PER_ROW];
 238
 239                 snprintf(buffer, sizeof(buffer),
 240                         (i == 0) ? ">%px: " : " %px: ", kaddr);
 241                 /*
 242                  * We should not pass a shadow pointer to generic
 243                  * function, because generic functions may try to
 244                  * access kasan mapping for the passed address.
 245                  */
 246                 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
 247                 print_hex_dump(KERN_ERR, buffer,
 248                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 249                         shadow_buf, SHADOW_BYTES_PER_ROW, 0);
 250
 251                 if (row_is_guilty(shadow_row, shadow))
 252                         pr_err("%*c\n",
 253                                 shadow_pointer_offset(shadow_row, shadow),
 254                                 '^');
 255
 256                 shadow_row += SHADOW_BYTES_PER_ROW;
 257         }
 258 }
 259
 260 static bool report_enabled(void)
 261 {
 262         if (current->kasan_depth)
 263                 return false;
 264         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 265                 return true;
 266         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 267 }
 268
 269 void kasan_report_invalid_free(void *object, unsigned long ip)
 270 {
 271         unsigned long flags;
 272
 273         start_report(&flags);
 274         pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
 275         print_tags(get_tag(object), reset_tag(object));
 276         object = reset_tag(object);
 277         pr_err("\n");
 278         print_address_description(object);
 279         pr_err("\n");
 280         print_shadow_for_address(object);
 281         end_report(&flags);
 282 }
 283
 284 void kasan_report(unsigned long addr, size_t size,
 285                 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 }