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/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 33 /* Shadow layout customization. */ 34 #define SHADOW_BYTES_PER_BLOCK 1 35 #define SHADOW_BLOCKS_PER_ROW 16 36 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK) 37 #define SHADOW_ROWS_AROUND_ADDR 2 38 39 static const void *find_first_bad_addr(const void *addr, size_t size) 40 { 41 u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr); 42 const void *first_bad_addr = addr; 43 44 while (!shadow_val && first_bad_addr < addr + size) { 45 first_bad_addr += KASAN_SHADOW_SCALE_SIZE; 46 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr); 47 } 48 return first_bad_addr; 49 } 50 51 static void print_error_description(struct kasan_access_info *info) 52 { 53 const char *bug_type = "unknown-crash"; 54 u8 *shadow_addr; 55 56 info->first_bad_addr = find_first_bad_addr(info->access_addr, 57 info->access_size); 58 59 shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr); 60 61 /* 62 * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look 63 * at the next shadow byte to determine the type of the bad access. 64 */ 65 if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1) 66 shadow_addr++; 67 68 switch (*shadow_addr) { 69 case 0 ... KASAN_SHADOW_SCALE_SIZE - 1: 70 /* 71 * In theory it's still possible to see these shadow values 72 * due to a data race in the kernel code. 73 */ 74 bug_type = "out-of-bounds"; 75 break; 76 case KASAN_PAGE_REDZONE: 77 case KASAN_KMALLOC_REDZONE: 78 bug_type = "slab-out-of-bounds"; 79 break; 80 case KASAN_GLOBAL_REDZONE: 81 bug_type = "global-out-of-bounds"; 82 break; 83 case KASAN_STACK_LEFT: 84 case KASAN_STACK_MID: 85 case KASAN_STACK_RIGHT: 86 case KASAN_STACK_PARTIAL: 87 bug_type = "stack-out-of-bounds"; 88 break; 89 case KASAN_FREE_PAGE: 90 case KASAN_KMALLOC_FREE: 91 bug_type = "use-after-free"; 92 break; 93 case KASAN_USE_AFTER_SCOPE: 94 bug_type = "use-after-scope"; 95 break; 96 } 97 98 pr_err("BUG: KASAN: %s in %pS at addr %p\n", 99 bug_type, (void *)info->ip, 100 info->access_addr); 101 pr_err("%s of size %zu by task %s/%d\n", 102 info->is_write ? "Write" : "Read", 103 info->access_size, current->comm, task_pid_nr(current)); 104 } 105 106 static inline bool kernel_or_module_addr(const void *addr) 107 { 108 if (addr >= (void *)_stext && addr < (void *)_end) 109 return true; 110 if (is_module_address((unsigned long)addr)) 111 return true; 112 return false; 113 } 114 115 static inline bool init_task_stack_addr(const void *addr) 116 { 117 return addr >= (void *)&init_thread_union.stack && 118 (addr <= (void *)&init_thread_union.stack + 119 sizeof(init_thread_union.stack)); 120 } 121 122 static DEFINE_SPINLOCK(report_lock); 123 124 static void kasan_start_report(unsigned long *flags) 125 { 126 /* 127 * Make sure we don't end up in loop. 128 */ 129 kasan_disable_current(); 130 spin_lock_irqsave(&report_lock, *flags); 131 pr_err("==================================================================\n"); 132 } 133 134 static void kasan_end_report(unsigned long *flags) 135 { 136 pr_err("==================================================================\n"); 137 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); 138 spin_unlock_irqrestore(&report_lock, *flags); 139 kasan_enable_current(); 140 } 141 142 static void print_track(struct kasan_track *track) 143 { 144 pr_err("PID = %u\n", track->pid); 145 if (track->stack) { 146 struct stack_trace trace; 147 148 depot_fetch_stack(track->stack, &trace); 149 print_stack_trace(&trace, 0); 150 } else { 151 pr_err("(stack is not available)\n"); 152 } 153 } 154 155 static void kasan_object_err(struct kmem_cache *cache, void *object) 156 { 157 struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object); 158 159 dump_stack(); 160 pr_err("Object at %p, in cache %s size: %d\n", object, cache->name, 161 cache->object_size); 162 163 if (!(cache->flags & SLAB_KASAN)) 164 return; 165 166 pr_err("Allocated:\n"); 167 print_track(&alloc_info->alloc_track); 168 pr_err("Freed:\n"); 169 print_track(&alloc_info->free_track); 170 } 171 172 void kasan_report_double_free(struct kmem_cache *cache, void *object, 173 s8 shadow) 174 { 175 unsigned long flags; 176 177 kasan_start_report(&flags); 178 pr_err("BUG: Double free or freeing an invalid pointer\n"); 179 pr_err("Unexpected shadow byte: 0x%hhX\n", shadow); 180 kasan_object_err(cache, object); 181 kasan_end_report(&flags); 182 } 183 184 static void print_address_description(struct kasan_access_info *info) 185 { 186 const void *addr = info->access_addr; 187 188 if ((addr >= (void *)PAGE_OFFSET) && 189 (addr < high_memory)) { 190 struct page *page = virt_to_head_page(addr); 191 192 if (PageSlab(page)) { 193 void *object; 194 struct kmem_cache *cache = page->slab_cache; 195 object = nearest_obj(cache, page, 196 (void *)info->access_addr); 197 kasan_object_err(cache, object); 198 return; 199 } 200 dump_page(page, "kasan: bad access detected"); 201 } 202 203 if (kernel_or_module_addr(addr)) { 204 if (!init_task_stack_addr(addr)) 205 pr_err("Address belongs to variable %pS\n", addr); 206 } 207 dump_stack(); 208 } 209 210 static bool row_is_guilty(const void *row, const void *guilty) 211 { 212 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW); 213 } 214 215 static int shadow_pointer_offset(const void *row, const void *shadow) 216 { 217 /* The length of ">ff00ff00ff00ff00: " is 218 * 3 + (BITS_PER_LONG/8)*2 chars. 219 */ 220 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 + 221 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1; 222 } 223 224 static void print_shadow_for_address(const void *addr) 225 { 226 int i; 227 const void *shadow = kasan_mem_to_shadow(addr); 228 const void *shadow_row; 229 230 shadow_row = (void *)round_down((unsigned long)shadow, 231 SHADOW_BYTES_PER_ROW) 232 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW; 233 234 pr_err("Memory state around the buggy address:\n"); 235 236 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) { 237 const void *kaddr = kasan_shadow_to_mem(shadow_row); 238 char buffer[4 + (BITS_PER_LONG/8)*2]; 239 char shadow_buf[SHADOW_BYTES_PER_ROW]; 240 241 snprintf(buffer, sizeof(buffer), 242 (i == 0) ? ">%p: " : " %p: ", kaddr); 243 /* 244 * We should not pass a shadow pointer to generic 245 * function, because generic functions may try to 246 * access kasan mapping for the passed address. 247 */ 248 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW); 249 print_hex_dump(KERN_ERR, buffer, 250 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1, 251 shadow_buf, SHADOW_BYTES_PER_ROW, 0); 252 253 if (row_is_guilty(shadow_row, shadow)) 254 pr_err("%*c\n", 255 shadow_pointer_offset(shadow_row, shadow), 256 '^'); 257 258 shadow_row += SHADOW_BYTES_PER_ROW; 259 } 260 } 261 262 static void kasan_report_error(struct kasan_access_info *info) 263 { 264 unsigned long flags; 265 const char *bug_type; 266 267 kasan_start_report(&flags); 268 269 if (info->access_addr < 270 kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) { 271 if ((unsigned long)info->access_addr < PAGE_SIZE) 272 bug_type = "null-ptr-deref"; 273 else if ((unsigned long)info->access_addr < TASK_SIZE) 274 bug_type = "user-memory-access"; 275 else 276 bug_type = "wild-memory-access"; 277 pr_err("BUG: KASAN: %s on address %p\n", 278 bug_type, info->access_addr); 279 pr_err("%s of size %zu by task %s/%d\n", 280 info->is_write ? "Write" : "Read", 281 info->access_size, current->comm, 282 task_pid_nr(current)); 283 dump_stack(); 284 } else { 285 print_error_description(info); 286 print_address_description(info); 287 print_shadow_for_address(info->first_bad_addr); 288 } 289 290 kasan_end_report(&flags); 291 } 292 293 void kasan_report(unsigned long addr, size_t size, 294 bool is_write, unsigned long ip) 295 { 296 struct kasan_access_info info; 297 298 if (likely(!kasan_report_enabled())) 299 return; 300 301 info.access_addr = (void *)addr; 302 info.access_size = size; 303 info.is_write = is_write; 304 info.ip = ip; 305 306 kasan_report_error(&info); 307 } 308 309 310 #define DEFINE_ASAN_REPORT_LOAD(size) \ 311 void __asan_report_load##size##_noabort(unsigned long addr) \ 312 { \ 313 kasan_report(addr, size, false, _RET_IP_); \ 314 } \ 315 EXPORT_SYMBOL(__asan_report_load##size##_noabort) 316 317 #define DEFINE_ASAN_REPORT_STORE(size) \ 318 void __asan_report_store##size##_noabort(unsigned long addr) \ 319 { \ 320 kasan_report(addr, size, true, _RET_IP_); \ 321 } \ 322 EXPORT_SYMBOL(__asan_report_store##size##_noabort) 323 324 DEFINE_ASAN_REPORT_LOAD(1); 325 DEFINE_ASAN_REPORT_LOAD(2); 326 DEFINE_ASAN_REPORT_LOAD(4); 327 DEFINE_ASAN_REPORT_LOAD(8); 328 DEFINE_ASAN_REPORT_LOAD(16); 329 DEFINE_ASAN_REPORT_STORE(1); 330 DEFINE_ASAN_REPORT_STORE(2); 331 DEFINE_ASAN_REPORT_STORE(4); 332 DEFINE_ASAN_REPORT_STORE(8); 333 DEFINE_ASAN_REPORT_STORE(16); 334 335 void __asan_report_load_n_noabort(unsigned long addr, size_t size) 336 { 337 kasan_report(addr, size, false, _RET_IP_); 338 } 339 EXPORT_SYMBOL(__asan_report_load_n_noabort); 340 341 void __asan_report_store_n_noabort(unsigned long addr, size_t size) 342 { 343 kasan_report(addr, size, true, _RET_IP_); 344 } 345 EXPORT_SYMBOL(__asan_report_store_n_noabort); 346