mm/kasan/report_generic.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * This file contains generic KASAN specific error reporting code.
0004  *
0005  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
0006  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
0007  *
0008  * Some code borrowed from https://github.com/xairy/kasan-prototype by
0009  *        Andrey Konovalov <andreyknvl@gmail.com>
0010  */
0011
0012 #include <linux/bitops.h>
0013 #include <linux/ftrace.h>
0014 #include <linux/init.h>
0015 #include <linux/kernel.h>
0016 #include <linux/mm.h>
0017 #include <linux/printk.h>
0018 #include <linux/sched.h>
0019 #include <linux/sched/task_stack.h>
0020 #include <linux/slab.h>
0021 #include <linux/stackdepot.h>
0022 #include <linux/stacktrace.h>
0023 #include <linux/string.h>
0024 #include <linux/types.h>
0025 #include <linux/kasan.h>
0026 #include <linux/module.h>
0027
0028 #include <asm/sections.h>
0029
0030 #include "kasan.h"
0031 #include "../slab.h"
0032
0033 void *kasan_find_first_bad_addr(void *addr, size_t size)
0034 {
0035     void *p = addr;
0036
0037     if (!addr_has_metadata(p))
0038         return p;
0039
0040     while (p < addr + size && !(*(u8 *)kasan_mem_to_shadow(p)))
0041         p += KASAN_GRANULE_SIZE;
0042
0043     return p;
0044 }
0045
0046 static const char *get_shadow_bug_type(struct kasan_report_info *info)
0047 {
0048     const char *bug_type = "unknown-crash";
0049     u8 *shadow_addr;
0050
0051     shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
0052
0053     /*
0054      * If shadow byte value is in [0, KASAN_GRANULE_SIZE) we can look
0055      * at the next shadow byte to determine the type of the bad access.
0056      */
0057     if (*shadow_addr > 0 && *shadow_addr <= KASAN_GRANULE_SIZE - 1)
0058         shadow_addr++;
0059
0060     switch (*shadow_addr) {
0061     case 0 ... KASAN_GRANULE_SIZE - 1:
0062         /*
0063          * In theory it's still possible to see these shadow values
0064          * due to a data race in the kernel code.
0065          */
0066         bug_type = "out-of-bounds";
0067         break;
0068     case KASAN_PAGE_REDZONE:
0069     case KASAN_SLAB_REDZONE:
0070         bug_type = "slab-out-of-bounds";
0071         break;
0072     case KASAN_GLOBAL_REDZONE:
0073         bug_type = "global-out-of-bounds";
0074         break;
0075     case KASAN_STACK_LEFT:
0076     case KASAN_STACK_MID:
0077     case KASAN_STACK_RIGHT:
0078     case KASAN_STACK_PARTIAL:
0079         bug_type = "stack-out-of-bounds";
0080         break;
0081     case KASAN_PAGE_FREE:
0082     case KASAN_SLAB_FREE:
0083     case KASAN_SLAB_FREETRACK:
0084         bug_type = "use-after-free";
0085         break;
0086     case KASAN_ALLOCA_LEFT:
0087     case KASAN_ALLOCA_RIGHT:
0088         bug_type = "alloca-out-of-bounds";
0089         break;
0090     case KASAN_VMALLOC_INVALID:
0091         bug_type = "vmalloc-out-of-bounds";
0092         break;
0093     }
0094
0095     return bug_type;
0096 }
0097
0098 static const char *get_wild_bug_type(struct kasan_report_info *info)
0099 {
0100     const char *bug_type = "unknown-crash";
0101
0102     if ((unsigned long)info->access_addr < PAGE_SIZE)
0103         bug_type = "null-ptr-deref";
0104     else if ((unsigned long)info->access_addr < TASK_SIZE)
0105         bug_type = "user-memory-access";
0106     else
0107         bug_type = "wild-memory-access";
0108
0109     return bug_type;
0110 }
0111
0112 const char *kasan_get_bug_type(struct kasan_report_info *info)
0113 {
0114     /*
0115      * If access_size is a negative number, then it has reason to be
0116      * defined as out-of-bounds bug type.
0117      *
0118      * Casting negative numbers to size_t would indeed turn up as
0119      * a large size_t and its value will be larger than ULONG_MAX/2,
0120      * so that this can qualify as out-of-bounds.
0121      */
0122     if (info->access_addr + info->access_size < info->access_addr)
0123         return "out-of-bounds";
0124
0125     if (addr_has_metadata(info->access_addr))
0126         return get_shadow_bug_type(info);
0127     return get_wild_bug_type(info);
0128 }
0129
0130 void kasan_metadata_fetch_row(char *buffer, void *row)
0131 {
0132     memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
0133 }
0134
0135 #ifdef CONFIG_KASAN_STACK
0136 static bool __must_check tokenize_frame_descr(const char **frame_descr,
0137                           char *token, size_t max_tok_len,
0138                           unsigned long *value)
0139 {
0140     const char *sep = strchr(*frame_descr, ' ');
0141
0142     if (sep == NULL)
0143         sep = *frame_descr + strlen(*frame_descr);
0144
0145     if (token != NULL) {
0146         const size_t tok_len = sep - *frame_descr;
0147
0148         if (tok_len + 1 > max_tok_len) {
0149             pr_err("KASAN internal error: frame description too long: %s\n",
0150                    *frame_descr);
0151             return false;
0152         }
0153
0154         /* Copy token (+ 1 byte for '\0'). */
0155         strscpy(token, *frame_descr, tok_len + 1);
0156     }
0157
0158     /* Advance frame_descr past separator. */
0159     *frame_descr = sep + 1;
0160
0161     if (value != NULL && kstrtoul(token, 10, value)) {
0162         pr_err("KASAN internal error: not a valid number: %s\n", token);
0163         return false;
0164     }
0165
0166     return true;
0167 }
0168
0169 static void print_decoded_frame_descr(const char *frame_descr)
0170 {
0171     /*
0172      * We need to parse the following string:
0173      *    "n alloc_1 alloc_2 ... alloc_n"
0174      * where alloc_i looks like
0175      *    "offset size len name"
0176      * or "offset size len name:line".
0177      */
0178
0179     char token[64];
0180     unsigned long num_objects;
0181
0182     if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
0183                   &num_objects))
0184         return;
0185
0186     pr_err("\n");
0187     pr_err("This frame has %lu %s:\n", num_objects,
0188            num_objects == 1 ? "object" : "objects");
0189
0190     while (num_objects--) {
0191         unsigned long offset;
0192         unsigned long size;
0193
0194         /* access offset */
0195         if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
0196                       &offset))
0197             return;
0198         /* access size */
0199         if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
0200                       &size))
0201             return;
0202         /* name length (unused) */
0203         if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
0204             return;
0205         /* object name */
0206         if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
0207                       NULL))
0208             return;
0209
0210         /* Strip line number; without filename it's not very helpful. */
0211         strreplace(token, ':', '\0');
0212
0213         /* Finally, print object information. */
0214         pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
0215     }
0216 }
0217
0218 /* Returns true only if the address is on the current task's stack. */
0219 static bool __must_check get_address_stack_frame_info(const void *addr,
0220                               unsigned long *offset,
0221                               const char **frame_descr,
0222                               const void **frame_pc)
0223 {
0224     unsigned long aligned_addr;
0225     unsigned long mem_ptr;
0226     const u8 *shadow_bottom;
0227     const u8 *shadow_ptr;
0228     const unsigned long *frame;
0229
0230     BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
0231
0232     aligned_addr = round_down((unsigned long)addr, sizeof(long));
0233     mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE);
0234     shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
0235     shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
0236
0237     while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
0238         shadow_ptr--;
0239         mem_ptr -= KASAN_GRANULE_SIZE;
0240     }
0241
0242     while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
0243         shadow_ptr--;
0244         mem_ptr -= KASAN_GRANULE_SIZE;
0245     }
0246
0247     if (shadow_ptr < shadow_bottom)
0248         return false;
0249
0250     frame = (const unsigned long *)(mem_ptr + KASAN_GRANULE_SIZE);
0251     if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
0252         pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
0253                frame[0]);
0254         return false;
0255     }
0256
0257     *offset = (unsigned long)addr - (unsigned long)frame;
0258     *frame_descr = (const char *)frame[1];
0259     *frame_pc = (void *)frame[2];
0260
0261     return true;
0262 }
0263
0264 void kasan_print_address_stack_frame(const void *addr)
0265 {
0266     unsigned long offset;
0267     const char *frame_descr;
0268     const void *frame_pc;
0269
0270     if (WARN_ON(!object_is_on_stack(addr)))
0271         return;
0272
0273     pr_err("The buggy address belongs to stack of task %s/%d\n",
0274            current->comm, task_pid_nr(current));
0275
0276     if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
0277                       &frame_pc))
0278         return;
0279
0280     pr_err(" and is located at offset %lu in frame:\n", offset);
0281     pr_err(" %pS\n", frame_pc);
0282
0283     if (!frame_descr)
0284         return;
0285
0286     print_decoded_frame_descr(frame_descr);
0287 }
0288 #endif /* CONFIG_KASAN_STACK */
0289
0290 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
0291 void __asan_report_load##size##_noabort(unsigned long addr) \
0292 {                                                         \
0293     kasan_report(addr, size, false, _RET_IP_);    \
0294 }                                                         \
0295 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
0296
0297 #define DEFINE_ASAN_REPORT_STORE(size)                     \
0298 void __asan_report_store##size##_noabort(unsigned long addr) \
0299 {                                                          \
0300     kasan_report(addr, size, true, _RET_IP_);      \
0301 }                                                          \
0302 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
0303
0304 DEFINE_ASAN_REPORT_LOAD(1);
0305 DEFINE_ASAN_REPORT_LOAD(2);
0306 DEFINE_ASAN_REPORT_LOAD(4);
0307 DEFINE_ASAN_REPORT_LOAD(8);
0308 DEFINE_ASAN_REPORT_LOAD(16);
0309 DEFINE_ASAN_REPORT_STORE(1);
0310 DEFINE_ASAN_REPORT_STORE(2);
0311 DEFINE_ASAN_REPORT_STORE(4);
0312 DEFINE_ASAN_REPORT_STORE(8);
0313 DEFINE_ASAN_REPORT_STORE(16);
0314
0315 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
0316 {
0317     kasan_report(addr, size, false, _RET_IP_);
0318 }
0319 EXPORT_SYMBOL(__asan_report_load_n_noabort);
0320
0321 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
0322 {
0323     kasan_report(addr, size, true, _RET_IP_);
0324 }
0325 EXPORT_SYMBOL(__asan_report_store_n_noabort);