linux/mm/kasan/report_generic.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * This file contains generic KASAN specific 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
  12#include <linux/bitops.h>
  13#include <linux/ftrace.h>
  14#include <linux/init.h>
  15#include <linux/kernel.h>
  16#include <linux/mm.h>
  17#include <linux/printk.h>
  18#include <linux/sched.h>
  19#include <linux/sched/task_stack.h>
  20#include <linux/slab.h>
  21#include <linux/stackdepot.h>
  22#include <linux/stacktrace.h>
  23#include <linux/string.h>
  24#include <linux/types.h>
  25#include <linux/kasan.h>
  26#include <linux/module.h>
  27
  28#include <asm/sections.h>
  29
  30#include "kasan.h"
  31#include "../slab.h"
  32
  33void *kasan_find_first_bad_addr(void *addr, size_t size)
  34{
  35        void *p = addr;
  36
  37        while (p < addr + size && !(*(u8 *)kasan_mem_to_shadow(p)))
  38                p += KASAN_GRANULE_SIZE;
  39        return p;
  40}
  41
  42static const char *get_shadow_bug_type(struct kasan_access_info *info)
  43{
  44        const char *bug_type = "unknown-crash";
  45        u8 *shadow_addr;
  46
  47        shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
  48
  49        /*
  50         * If shadow byte value is in [0, KASAN_GRANULE_SIZE) we can look
  51         * at the next shadow byte to determine the type of the bad access.
  52         */
  53        if (*shadow_addr > 0 && *shadow_addr <= KASAN_GRANULE_SIZE - 1)
  54                shadow_addr++;
  55
  56        switch (*shadow_addr) {
  57        case 0 ... KASAN_GRANULE_SIZE - 1:
  58                /*
  59                 * In theory it's still possible to see these shadow values
  60                 * due to a data race in the kernel code.
  61                 */
  62                bug_type = "out-of-bounds";
  63                break;
  64        case KASAN_PAGE_REDZONE:
  65        case KASAN_KMALLOC_REDZONE:
  66                bug_type = "slab-out-of-bounds";
  67                break;
  68        case KASAN_GLOBAL_REDZONE:
  69                bug_type = "global-out-of-bounds";
  70                break;
  71        case KASAN_STACK_LEFT:
  72        case KASAN_STACK_MID:
  73        case KASAN_STACK_RIGHT:
  74        case KASAN_STACK_PARTIAL:
  75                bug_type = "stack-out-of-bounds";
  76                break;
  77        case KASAN_FREE_PAGE:
  78        case KASAN_KMALLOC_FREE:
  79        case KASAN_KMALLOC_FREETRACK:
  80                bug_type = "use-after-free";
  81                break;
  82        case KASAN_ALLOCA_LEFT:
  83        case KASAN_ALLOCA_RIGHT:
  84                bug_type = "alloca-out-of-bounds";
  85                break;
  86        case KASAN_VMALLOC_INVALID:
  87                bug_type = "vmalloc-out-of-bounds";
  88                break;
  89        }
  90
  91        return bug_type;
  92}
  93
  94static const char *get_wild_bug_type(struct kasan_access_info *info)
  95{
  96        const char *bug_type = "unknown-crash";
  97
  98        if ((unsigned long)info->access_addr < PAGE_SIZE)
  99                bug_type = "null-ptr-deref";
 100        else if ((unsigned long)info->access_addr < TASK_SIZE)
 101                bug_type = "user-memory-access";
 102        else
 103                bug_type = "wild-memory-access";
 104
 105        return bug_type;
 106}
 107
 108const char *kasan_get_bug_type(struct kasan_access_info *info)
 109{
 110        /*
 111         * If access_size is a negative number, then it has reason to be
 112         * defined as out-of-bounds bug type.
 113         *
 114         * Casting negative numbers to size_t would indeed turn up as
 115         * a large size_t and its value will be larger than ULONG_MAX/2,
 116         * so that this can qualify as out-of-bounds.
 117         */
 118        if (info->access_addr + info->access_size < info->access_addr)
 119                return "out-of-bounds";
 120
 121        if (addr_has_metadata(info->access_addr))
 122                return get_shadow_bug_type(info);
 123        return get_wild_bug_type(info);
 124}
 125
 126void kasan_metadata_fetch_row(char *buffer, void *row)
 127{
 128        memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
 129}
 130
 131#ifdef CONFIG_KASAN_STACK
 132static bool __must_check tokenize_frame_descr(const char **frame_descr,
 133                                              char *token, size_t max_tok_len,
 134                                              unsigned long *value)
 135{
 136        const char *sep = strchr(*frame_descr, ' ');
 137
 138        if (sep == NULL)
 139                sep = *frame_descr + strlen(*frame_descr);
 140
 141        if (token != NULL) {
 142                const size_t tok_len = sep - *frame_descr;
 143
 144                if (tok_len + 1 > max_tok_len) {
 145                        pr_err("KASAN internal error: frame description too long: %s\n",
 146                               *frame_descr);
 147                        return false;
 148                }
 149
 150                /* Copy token (+ 1 byte for '\0'). */
 151                strscpy(token, *frame_descr, tok_len + 1);
 152        }
 153
 154        /* Advance frame_descr past separator. */
 155        *frame_descr = sep + 1;
 156
 157        if (value != NULL && kstrtoul(token, 10, value)) {
 158                pr_err("KASAN internal error: not a valid number: %s\n", token);
 159                return false;
 160        }
 161
 162        return true;
 163}
 164
 165static void print_decoded_frame_descr(const char *frame_descr)
 166{
 167        /*
 168         * We need to parse the following string:
 169         *    "n alloc_1 alloc_2 ... alloc_n"
 170         * where alloc_i looks like
 171         *    "offset size len name"
 172         * or "offset size len name:line".
 173         */
 174
 175        char token[64];
 176        unsigned long num_objects;
 177
 178        if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 179                                  &num_objects))
 180                return;
 181
 182        pr_err("\n");
 183        pr_err("this frame has %lu %s:\n", num_objects,
 184               num_objects == 1 ? "object" : "objects");
 185
 186        while (num_objects--) {
 187                unsigned long offset;
 188                unsigned long size;
 189
 190                /* access offset */
 191                if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 192                                          &offset))
 193                        return;
 194                /* access size */
 195                if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 196                                          &size))
 197                        return;
 198                /* name length (unused) */
 199                if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
 200                        return;
 201                /* object name */
 202                if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 203                                          NULL))
 204                        return;
 205
 206                /* Strip line number; without filename it's not very helpful. */
 207                strreplace(token, ':', '\0');
 208
 209                /* Finally, print object information. */
 210                pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
 211        }
 212}
 213
 214static bool __must_check get_address_stack_frame_info(const void *addr,
 215                                                      unsigned long *offset,
 216                                                      const char **frame_descr,
 217                                                      const void **frame_pc)
 218{
 219        unsigned long aligned_addr;
 220        unsigned long mem_ptr;
 221        const u8 *shadow_bottom;
 222        const u8 *shadow_ptr;
 223        const unsigned long *frame;
 224
 225        BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
 226
 227        /*
 228         * NOTE: We currently only support printing frame information for
 229         * accesses to the task's own stack.
 230         */
 231        if (!object_is_on_stack(addr))
 232                return false;
 233
 234        aligned_addr = round_down((unsigned long)addr, sizeof(long));
 235        mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE);
 236        shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
 237        shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
 238
 239        while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
 240                shadow_ptr--;
 241                mem_ptr -= KASAN_GRANULE_SIZE;
 242        }
 243
 244        while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
 245                shadow_ptr--;
 246                mem_ptr -= KASAN_GRANULE_SIZE;
 247        }
 248
 249        if (shadow_ptr < shadow_bottom)
 250                return false;
 251
 252        frame = (const unsigned long *)(mem_ptr + KASAN_GRANULE_SIZE);
 253        if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
 254                pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
 255                       frame[0]);
 256                return false;
 257        }
 258
 259        *offset = (unsigned long)addr - (unsigned long)frame;
 260        *frame_descr = (const char *)frame[1];
 261        *frame_pc = (void *)frame[2];
 262
 263        return true;
 264}
 265
 266void kasan_print_address_stack_frame(const void *addr)
 267{
 268        unsigned long offset;
 269        const char *frame_descr;
 270        const void *frame_pc;
 271
 272        if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
 273                                          &frame_pc))
 274                return;
 275
 276        /*
 277         * get_address_stack_frame_info only returns true if the given addr is
 278         * on the current task's stack.
 279         */
 280        pr_err("\n");
 281        pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n",
 282               addr, current->comm, task_pid_nr(current), offset);
 283        pr_err(" %pS\n", frame_pc);
 284
 285        if (!frame_descr)
 286                return;
 287
 288        print_decoded_frame_descr(frame_descr);
 289}
 290#endif /* CONFIG_KASAN_STACK */
 291
 292#define DEFINE_ASAN_REPORT_LOAD(size)                     \
 293void __asan_report_load##size##_noabort(unsigned long addr) \
 294{                                                         \
 295        kasan_report(addr, size, false, _RET_IP_);        \
 296}                                                         \
 297EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 298
 299#define DEFINE_ASAN_REPORT_STORE(size)                     \
 300void __asan_report_store##size##_noabort(unsigned long addr) \
 301{                                                          \
 302        kasan_report(addr, size, true, _RET_IP_);          \
 303}                                                          \
 304EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 305
 306DEFINE_ASAN_REPORT_LOAD(1);
 307DEFINE_ASAN_REPORT_LOAD(2);
 308DEFINE_ASAN_REPORT_LOAD(4);
 309DEFINE_ASAN_REPORT_LOAD(8);
 310DEFINE_ASAN_REPORT_LOAD(16);
 311DEFINE_ASAN_REPORT_STORE(1);
 312DEFINE_ASAN_REPORT_STORE(2);
 313DEFINE_ASAN_REPORT_STORE(4);
 314DEFINE_ASAN_REPORT_STORE(8);
 315DEFINE_ASAN_REPORT_STORE(16);
 316
 317void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 318{
 319        kasan_report(addr, size, false, _RET_IP_);
 320}
 321EXPORT_SYMBOL(__asan_report_load_n_noabort);
 322
 323void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 324{
 325        kasan_report(addr, size, true, _RET_IP_);
 326}
 327EXPORT_SYMBOL(__asan_report_store_n_noabort);
 328