1 /* 2 * This file contains error reporting code. 3 * 4 * Copyright (c) 2014 Samsung Electronics Co., Ltd. 5 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com> 6 * 7 * Some of code borrowed from https://github.com/xairy/linux by 8 * Andrey Konovalov <adech.fo@gmail.com> 9 * 10 * This program is free software; you can redistribute it and/or modify 11 * it under the terms of the GNU General Public License version 2 as 12 * published by the Free Software Foundation. 13 * 14 */ 15 16 #include <linux/kernel.h> 17 #include <linux/mm.h> 18 #include <linux/printk.h> 19 #include <linux/sched.h> 20 #include <linux/slab.h> 21 #include <linux/stacktrace.h> 22 #include <linux/string.h> 23 #include <linux/types.h> 24 #include <linux/kasan.h> 25 26 #include <asm/sections.h> 27 28 #include "kasan.h" 29 #include "../slab.h" 30 31 /* Shadow layout customization. */ 32 #define SHADOW_BYTES_PER_BLOCK 1 33 #define SHADOW_BLOCKS_PER_ROW 16 34 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK) 35 #define SHADOW_ROWS_AROUND_ADDR 2 36 37 static const void *find_first_bad_addr(const void *addr, size_t size) 38 { 39 u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr); 40 const void *first_bad_addr = addr; 41 42 while (!shadow_val && first_bad_addr < addr + size) { 43 first_bad_addr += KASAN_SHADOW_SCALE_SIZE; 44 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr); 45 } 46 return first_bad_addr; 47 } 48 49 static void print_error_description(struct kasan_access_info *info) 50 { 51 const char *bug_type = "unknown crash"; 52 u8 shadow_val; 53 54 info->first_bad_addr = find_first_bad_addr(info->access_addr, 55 info->access_size); 56 57 shadow_val = *(u8 *)kasan_mem_to_shadow(info->first_bad_addr); 58 59 switch (shadow_val) { 60 case KASAN_FREE_PAGE: 61 case KASAN_KMALLOC_FREE: 62 bug_type = "use after free"; 63 break; 64 case KASAN_PAGE_REDZONE: 65 case KASAN_KMALLOC_REDZONE: 66 case KASAN_GLOBAL_REDZONE: 67 case 0 ... KASAN_SHADOW_SCALE_SIZE - 1: 68 bug_type = "out of bounds access"; 69 break; 70 case KASAN_STACK_LEFT: 71 case KASAN_STACK_MID: 72 case KASAN_STACK_RIGHT: 73 case KASAN_STACK_PARTIAL: 74 bug_type = "out of bounds on stack"; 75 break; 76 } 77 78 pr_err("BUG: KASan: %s in %pS at addr %p\n", 79 bug_type, (void *)info->ip, 80 info->access_addr); 81 pr_err("%s of size %zu by task %s/%d\n", 82 info->is_write ? "Write" : "Read", 83 info->access_size, current->comm, task_pid_nr(current)); 84 } 85 86 static inline bool kernel_or_module_addr(const void *addr) 87 { 88 return (addr >= (void *)_stext && addr < (void *)_end) 89 || (addr >= (void *)MODULES_VADDR 90 && addr < (void *)MODULES_END); 91 } 92 93 static inline bool init_task_stack_addr(const void *addr) 94 { 95 return addr >= (void *)&init_thread_union.stack && 96 (addr <= (void *)&init_thread_union.stack + 97 sizeof(init_thread_union.stack)); 98 } 99 100 static void print_address_description(struct kasan_access_info *info) 101 { 102 const void *addr = info->access_addr; 103 104 if ((addr >= (void *)PAGE_OFFSET) && 105 (addr < high_memory)) { 106 struct page *page = virt_to_head_page(addr); 107 108 if (PageSlab(page)) { 109 void *object; 110 struct kmem_cache *cache = page->slab_cache; 111 void *last_object; 112 113 object = virt_to_obj(cache, page_address(page), addr); 114 last_object = page_address(page) + 115 page->objects * cache->size; 116 117 if (unlikely(object > last_object)) 118 object = last_object; /* we hit into padding */ 119 120 object_err(cache, page, object, 121 "kasan: bad access detected"); 122 return; 123 } 124 dump_page(page, "kasan: bad access detected"); 125 } 126 127 if (kernel_or_module_addr(addr)) { 128 if (!init_task_stack_addr(addr)) 129 pr_err("Address belongs to variable %pS\n", addr); 130 } 131 132 dump_stack(); 133 } 134 135 static bool row_is_guilty(const void *row, const void *guilty) 136 { 137 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW); 138 } 139 140 static int shadow_pointer_offset(const void *row, const void *shadow) 141 { 142 /* The length of ">ff00ff00ff00ff00: " is 143 * 3 + (BITS_PER_LONG/8)*2 chars. 144 */ 145 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 + 146 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1; 147 } 148 149 static void print_shadow_for_address(const void *addr) 150 { 151 int i; 152 const void *shadow = kasan_mem_to_shadow(addr); 153 const void *shadow_row; 154 155 shadow_row = (void *)round_down((unsigned long)shadow, 156 SHADOW_BYTES_PER_ROW) 157 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW; 158 159 pr_err("Memory state around the buggy address:\n"); 160 161 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) { 162 const void *kaddr = kasan_shadow_to_mem(shadow_row); 163 char buffer[4 + (BITS_PER_LONG/8)*2]; 164 165 snprintf(buffer, sizeof(buffer), 166 (i == 0) ? ">%p: " : " %p: ", kaddr); 167 168 kasan_disable_current(); 169 print_hex_dump(KERN_ERR, buffer, 170 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1, 171 shadow_row, SHADOW_BYTES_PER_ROW, 0); 172 kasan_enable_current(); 173 174 if (row_is_guilty(shadow_row, shadow)) 175 pr_err("%*c\n", 176 shadow_pointer_offset(shadow_row, shadow), 177 '^'); 178 179 shadow_row += SHADOW_BYTES_PER_ROW; 180 } 181 } 182 183 static DEFINE_SPINLOCK(report_lock); 184 185 void kasan_report_error(struct kasan_access_info *info) 186 { 187 unsigned long flags; 188 189 spin_lock_irqsave(&report_lock, flags); 190 pr_err("=================================" 191 "=================================\n"); 192 print_error_description(info); 193 print_address_description(info); 194 print_shadow_for_address(info->first_bad_addr); 195 pr_err("=================================" 196 "=================================\n"); 197 spin_unlock_irqrestore(&report_lock, flags); 198 } 199 200 void kasan_report_user_access(struct kasan_access_info *info) 201 { 202 unsigned long flags; 203 204 spin_lock_irqsave(&report_lock, flags); 205 pr_err("=================================" 206 "=================================\n"); 207 pr_err("BUG: KASan: user-memory-access on address %p\n", 208 info->access_addr); 209 pr_err("%s of size %zu by task %s/%d\n", 210 info->is_write ? "Write" : "Read", 211 info->access_size, current->comm, task_pid_nr(current)); 212 dump_stack(); 213 pr_err("=================================" 214 "=================================\n"); 215 spin_unlock_irqrestore(&report_lock, flags); 216 } 217 218 void kasan_report(unsigned long addr, size_t size, 219 bool is_write, unsigned long ip) 220 { 221 struct kasan_access_info info; 222 223 if (likely(!kasan_enabled())) 224 return; 225 226 info.access_addr = (void *)addr; 227 info.access_size = size; 228 info.is_write = is_write; 229 info.ip = ip; 230 kasan_report_error(&info); 231 } 232 233 234 #define DEFINE_ASAN_REPORT_LOAD(size) \ 235 void __asan_report_load##size##_noabort(unsigned long addr) \ 236 { \ 237 kasan_report(addr, size, false, _RET_IP_); \ 238 } \ 239 EXPORT_SYMBOL(__asan_report_load##size##_noabort) 240 241 #define DEFINE_ASAN_REPORT_STORE(size) \ 242 void __asan_report_store##size##_noabort(unsigned long addr) \ 243 { \ 244 kasan_report(addr, size, true, _RET_IP_); \ 245 } \ 246 EXPORT_SYMBOL(__asan_report_store##size##_noabort) 247 248 DEFINE_ASAN_REPORT_LOAD(1); 249 DEFINE_ASAN_REPORT_LOAD(2); 250 DEFINE_ASAN_REPORT_LOAD(4); 251 DEFINE_ASAN_REPORT_LOAD(8); 252 DEFINE_ASAN_REPORT_LOAD(16); 253 DEFINE_ASAN_REPORT_STORE(1); 254 DEFINE_ASAN_REPORT_STORE(2); 255 DEFINE_ASAN_REPORT_STORE(4); 256 DEFINE_ASAN_REPORT_STORE(8); 257 DEFINE_ASAN_REPORT_STORE(16); 258 259 void __asan_report_load_n_noabort(unsigned long addr, size_t size) 260 { 261 kasan_report(addr, size, false, _RET_IP_); 262 } 263 EXPORT_SYMBOL(__asan_report_load_n_noabort); 264 265 void __asan_report_store_n_noabort(unsigned long addr, size_t size) 266 { 267 kasan_report(addr, size, true, _RET_IP_); 268 } 269 EXPORT_SYMBOL(__asan_report_store_n_noabort); 270