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 code borrowed from https://github.com/xairy/kasan-prototype 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 #include <linux/module.h> 26 27 #include <asm/sections.h> 28 29 #include "kasan.h" 30 #include "../slab.h" 31 32 /* Shadow layout customization. */ 33 #define SHADOW_BYTES_PER_BLOCK 1 34 #define SHADOW_BLOCKS_PER_ROW 16 35 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK) 36 #define SHADOW_ROWS_AROUND_ADDR 2 37 38 static const void *find_first_bad_addr(const void *addr, size_t size) 39 { 40 u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr); 41 const void *first_bad_addr = addr; 42 43 while (!shadow_val && first_bad_addr < addr + size) { 44 first_bad_addr += KASAN_SHADOW_SCALE_SIZE; 45 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr); 46 } 47 return first_bad_addr; 48 } 49 50 static void print_error_description(struct kasan_access_info *info) 51 { 52 const char *bug_type = "unknown-crash"; 53 u8 *shadow_addr; 54 55 info->first_bad_addr = find_first_bad_addr(info->access_addr, 56 info->access_size); 57 58 shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr); 59 60 /* 61 * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look 62 * at the next shadow byte to determine the type of the bad access. 63 */ 64 if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1) 65 shadow_addr++; 66 67 switch (*shadow_addr) { 68 case 0 ... KASAN_SHADOW_SCALE_SIZE - 1: 69 /* 70 * In theory it's still possible to see these shadow values 71 * due to a data race in the kernel code. 72 */ 73 bug_type = "out-of-bounds"; 74 break; 75 case KASAN_PAGE_REDZONE: 76 case KASAN_KMALLOC_REDZONE: 77 bug_type = "slab-out-of-bounds"; 78 break; 79 case KASAN_GLOBAL_REDZONE: 80 bug_type = "global-out-of-bounds"; 81 break; 82 case KASAN_STACK_LEFT: 83 case KASAN_STACK_MID: 84 case KASAN_STACK_RIGHT: 85 case KASAN_STACK_PARTIAL: 86 bug_type = "stack-out-of-bounds"; 87 break; 88 case KASAN_FREE_PAGE: 89 case KASAN_KMALLOC_FREE: 90 bug_type = "use-after-free"; 91 break; 92 } 93 94 pr_err("BUG: KASAN: %s in %pS at addr %p\n", 95 bug_type, (void *)info->ip, 96 info->access_addr); 97 pr_err("%s of size %zu by task %s/%d\n", 98 info->is_write ? "Write" : "Read", 99 info->access_size, current->comm, task_pid_nr(current)); 100 } 101 102 static inline bool kernel_or_module_addr(const void *addr) 103 { 104 if (addr >= (void *)_stext && addr < (void *)_end) 105 return true; 106 if (is_module_address((unsigned long)addr)) 107 return true; 108 return false; 109 } 110 111 static inline bool init_task_stack_addr(const void *addr) 112 { 113 return addr >= (void *)&init_thread_union.stack && 114 (addr <= (void *)&init_thread_union.stack + 115 sizeof(init_thread_union.stack)); 116 } 117 118 static void print_address_description(struct kasan_access_info *info) 119 { 120 const void *addr = info->access_addr; 121 122 if ((addr >= (void *)PAGE_OFFSET) && 123 (addr < high_memory)) { 124 struct page *page = virt_to_head_page(addr); 125 126 if (PageSlab(page)) { 127 void *object; 128 struct kmem_cache *cache = page->slab_cache; 129 void *last_object; 130 131 object = virt_to_obj(cache, page_address(page), addr); 132 last_object = page_address(page) + 133 page->objects * cache->size; 134 135 if (unlikely(object > last_object)) 136 object = last_object; /* we hit into padding */ 137 138 object_err(cache, page, object, 139 "kasan: bad access detected"); 140 return; 141 } 142 dump_page(page, "kasan: bad access detected"); 143 } 144 145 if (kernel_or_module_addr(addr)) { 146 if (!init_task_stack_addr(addr)) 147 pr_err("Address belongs to variable %pS\n", addr); 148 } 149 150 dump_stack(); 151 } 152 153 static bool row_is_guilty(const void *row, const void *guilty) 154 { 155 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW); 156 } 157 158 static int shadow_pointer_offset(const void *row, const void *shadow) 159 { 160 /* The length of ">ff00ff00ff00ff00: " is 161 * 3 + (BITS_PER_LONG/8)*2 chars. 162 */ 163 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 + 164 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1; 165 } 166 167 static void print_shadow_for_address(const void *addr) 168 { 169 int i; 170 const void *shadow = kasan_mem_to_shadow(addr); 171 const void *shadow_row; 172 173 shadow_row = (void *)round_down((unsigned long)shadow, 174 SHADOW_BYTES_PER_ROW) 175 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW; 176 177 pr_err("Memory state around the buggy address:\n"); 178 179 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) { 180 const void *kaddr = kasan_shadow_to_mem(shadow_row); 181 char buffer[4 + (BITS_PER_LONG/8)*2]; 182 char shadow_buf[SHADOW_BYTES_PER_ROW]; 183 184 snprintf(buffer, sizeof(buffer), 185 (i == 0) ? ">%p: " : " %p: ", kaddr); 186 /* 187 * We should not pass a shadow pointer to generic 188 * function, because generic functions may try to 189 * access kasan mapping for the passed address. 190 */ 191 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW); 192 print_hex_dump(KERN_ERR, buffer, 193 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1, 194 shadow_buf, SHADOW_BYTES_PER_ROW, 0); 195 196 if (row_is_guilty(shadow_row, shadow)) 197 pr_err("%*c\n", 198 shadow_pointer_offset(shadow_row, shadow), 199 '^'); 200 201 shadow_row += SHADOW_BYTES_PER_ROW; 202 } 203 } 204 205 static DEFINE_SPINLOCK(report_lock); 206 207 static void kasan_report_error(struct kasan_access_info *info) 208 { 209 unsigned long flags; 210 const char *bug_type; 211 212 /* 213 * Make sure we don't end up in loop. 214 */ 215 kasan_disable_current(); 216 spin_lock_irqsave(&report_lock, flags); 217 pr_err("=================================" 218 "=================================\n"); 219 if (info->access_addr < 220 kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) { 221 if ((unsigned long)info->access_addr < PAGE_SIZE) 222 bug_type = "null-ptr-deref"; 223 else if ((unsigned long)info->access_addr < TASK_SIZE) 224 bug_type = "user-memory-access"; 225 else 226 bug_type = "wild-memory-access"; 227 pr_err("BUG: KASAN: %s on address %p\n", 228 bug_type, info->access_addr); 229 pr_err("%s of size %zu by task %s/%d\n", 230 info->is_write ? "Write" : "Read", 231 info->access_size, current->comm, 232 task_pid_nr(current)); 233 dump_stack(); 234 } else { 235 print_error_description(info); 236 print_address_description(info); 237 print_shadow_for_address(info->first_bad_addr); 238 } 239 pr_err("=================================" 240 "=================================\n"); 241 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); 242 spin_unlock_irqrestore(&report_lock, flags); 243 kasan_enable_current(); 244 } 245 246 void kasan_report(unsigned long addr, size_t size, 247 bool is_write, unsigned long ip) 248 { 249 struct kasan_access_info info; 250 251 if (likely(!kasan_report_enabled())) 252 return; 253 254 info.access_addr = (void *)addr; 255 info.access_size = size; 256 info.is_write = is_write; 257 info.ip = ip; 258 259 kasan_report_error(&info); 260 } 261 262 263 #define DEFINE_ASAN_REPORT_LOAD(size) \ 264 void __asan_report_load##size##_noabort(unsigned long addr) \ 265 { \ 266 kasan_report(addr, size, false, _RET_IP_); \ 267 } \ 268 EXPORT_SYMBOL(__asan_report_load##size##_noabort) 269 270 #define DEFINE_ASAN_REPORT_STORE(size) \ 271 void __asan_report_store##size##_noabort(unsigned long addr) \ 272 { \ 273 kasan_report(addr, size, true, _RET_IP_); \ 274 } \ 275 EXPORT_SYMBOL(__asan_report_store##size##_noabort) 276 277 DEFINE_ASAN_REPORT_LOAD(1); 278 DEFINE_ASAN_REPORT_LOAD(2); 279 DEFINE_ASAN_REPORT_LOAD(4); 280 DEFINE_ASAN_REPORT_LOAD(8); 281 DEFINE_ASAN_REPORT_LOAD(16); 282 DEFINE_ASAN_REPORT_STORE(1); 283 DEFINE_ASAN_REPORT_STORE(2); 284 DEFINE_ASAN_REPORT_STORE(4); 285 DEFINE_ASAN_REPORT_STORE(8); 286 DEFINE_ASAN_REPORT_STORE(16); 287 288 void __asan_report_load_n_noabort(unsigned long addr, size_t size) 289 { 290 kasan_report(addr, size, false, _RET_IP_); 291 } 292 EXPORT_SYMBOL(__asan_report_load_n_noabort); 293 294 void __asan_report_store_n_noabort(unsigned long addr, size_t size) 295 { 296 kasan_report(addr, size, true, _RET_IP_); 297 } 298 EXPORT_SYMBOL(__asan_report_store_n_noabort); 299