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/bitops.h> 17 #include <linux/ftrace.h> 18 #include <linux/init.h> 19 #include <linux/kernel.h> 20 #include <linux/mm.h> 21 #include <linux/printk.h> 22 #include <linux/sched.h> 23 #include <linux/slab.h> 24 #include <linux/stackdepot.h> 25 #include <linux/stacktrace.h> 26 #include <linux/string.h> 27 #include <linux/types.h> 28 #include <linux/kasan.h> 29 #include <linux/module.h> 30 31 #include <asm/sections.h> 32 33 #include "kasan.h" 34 #include "../slab.h" 35 36 /* Shadow layout customization. */ 37 #define SHADOW_BYTES_PER_BLOCK 1 38 #define SHADOW_BLOCKS_PER_ROW 16 39 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK) 40 #define SHADOW_ROWS_AROUND_ADDR 2 41 42 static const void *find_first_bad_addr(const void *addr, size_t size) 43 { 44 u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr); 45 const void *first_bad_addr = addr; 46 47 while (!shadow_val && first_bad_addr < addr + size) { 48 first_bad_addr += KASAN_SHADOW_SCALE_SIZE; 49 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr); 50 } 51 return first_bad_addr; 52 } 53 54 static void print_error_description(struct kasan_access_info *info) 55 { 56 const char *bug_type = "unknown-crash"; 57 u8 *shadow_addr; 58 59 info->first_bad_addr = find_first_bad_addr(info->access_addr, 60 info->access_size); 61 62 shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr); 63 64 /* 65 * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look 66 * at the next shadow byte to determine the type of the bad access. 67 */ 68 if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1) 69 shadow_addr++; 70 71 switch (*shadow_addr) { 72 case 0 ... KASAN_SHADOW_SCALE_SIZE - 1: 73 /* 74 * In theory it's still possible to see these shadow values 75 * due to a data race in the kernel code. 76 */ 77 bug_type = "out-of-bounds"; 78 break; 79 case KASAN_PAGE_REDZONE: 80 case KASAN_KMALLOC_REDZONE: 81 bug_type = "slab-out-of-bounds"; 82 break; 83 case KASAN_GLOBAL_REDZONE: 84 bug_type = "global-out-of-bounds"; 85 break; 86 case KASAN_STACK_LEFT: 87 case KASAN_STACK_MID: 88 case KASAN_STACK_RIGHT: 89 case KASAN_STACK_PARTIAL: 90 bug_type = "stack-out-of-bounds"; 91 break; 92 case KASAN_FREE_PAGE: 93 case KASAN_KMALLOC_FREE: 94 bug_type = "use-after-free"; 95 break; 96 case KASAN_USE_AFTER_SCOPE: 97 bug_type = "use-after-scope"; 98 break; 99 } 100 101 pr_err("BUG: KASAN: %s in %pS at addr %p\n", 102 bug_type, (void *)info->ip, 103 info->access_addr); 104 pr_err("%s of size %zu by task %s/%d\n", 105 info->is_write ? "Write" : "Read", 106 info->access_size, current->comm, task_pid_nr(current)); 107 } 108 109 static inline bool kernel_or_module_addr(const void *addr) 110 { 111 if (addr >= (void *)_stext && addr < (void *)_end) 112 return true; 113 if (is_module_address((unsigned long)addr)) 114 return true; 115 return false; 116 } 117 118 static inline bool init_task_stack_addr(const void *addr) 119 { 120 return addr >= (void *)&init_thread_union.stack && 121 (addr <= (void *)&init_thread_union.stack + 122 sizeof(init_thread_union.stack)); 123 } 124 125 static DEFINE_SPINLOCK(report_lock); 126 127 static void kasan_start_report(unsigned long *flags) 128 { 129 /* 130 * Make sure we don't end up in loop. 131 */ 132 kasan_disable_current(); 133 spin_lock_irqsave(&report_lock, *flags); 134 pr_err("==================================================================\n"); 135 } 136 137 static void kasan_end_report(unsigned long *flags) 138 { 139 pr_err("==================================================================\n"); 140 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); 141 spin_unlock_irqrestore(&report_lock, *flags); 142 if (panic_on_warn) 143 panic("panic_on_warn set ...\n"); 144 kasan_enable_current(); 145 } 146 147 static void print_track(struct kasan_track *track) 148 { 149 pr_err("PID = %u\n", track->pid); 150 if (track->stack) { 151 struct stack_trace trace; 152 153 depot_fetch_stack(track->stack, &trace); 154 print_stack_trace(&trace, 0); 155 } else { 156 pr_err("(stack is not available)\n"); 157 } 158 } 159 160 static void kasan_object_err(struct kmem_cache *cache, void *object) 161 { 162 struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object); 163 164 dump_stack(); 165 pr_err("Object at %p, in cache %s size: %d\n", object, cache->name, 166 cache->object_size); 167 168 if (!(cache->flags & SLAB_KASAN)) 169 return; 170 171 pr_err("Allocated:\n"); 172 print_track(&alloc_info->alloc_track); 173 pr_err("Freed:\n"); 174 print_track(&alloc_info->free_track); 175 } 176 177 void kasan_report_double_free(struct kmem_cache *cache, void *object, 178 s8 shadow) 179 { 180 unsigned long flags; 181 182 kasan_start_report(&flags); 183 pr_err("BUG: Double free or freeing an invalid pointer\n"); 184 pr_err("Unexpected shadow byte: 0x%hhX\n", shadow); 185 kasan_object_err(cache, object); 186 kasan_end_report(&flags); 187 } 188 189 static void print_address_description(struct kasan_access_info *info) 190 { 191 const void *addr = info->access_addr; 192 193 if ((addr >= (void *)PAGE_OFFSET) && 194 (addr < high_memory)) { 195 struct page *page = virt_to_head_page(addr); 196 197 if (PageSlab(page)) { 198 void *object; 199 struct kmem_cache *cache = page->slab_cache; 200 object = nearest_obj(cache, page, 201 (void *)info->access_addr); 202 kasan_object_err(cache, object); 203 return; 204 } 205 dump_page(page, "kasan: bad access detected"); 206 } 207 208 if (kernel_or_module_addr(addr)) { 209 if (!init_task_stack_addr(addr)) 210 pr_err("Address belongs to variable %pS\n", addr); 211 } 212 dump_stack(); 213 } 214 215 static bool row_is_guilty(const void *row, const void *guilty) 216 { 217 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW); 218 } 219 220 static int shadow_pointer_offset(const void *row, const void *shadow) 221 { 222 /* The length of ">ff00ff00ff00ff00: " is 223 * 3 + (BITS_PER_LONG/8)*2 chars. 224 */ 225 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 + 226 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1; 227 } 228 229 static void print_shadow_for_address(const void *addr) 230 { 231 int i; 232 const void *shadow = kasan_mem_to_shadow(addr); 233 const void *shadow_row; 234 235 shadow_row = (void *)round_down((unsigned long)shadow, 236 SHADOW_BYTES_PER_ROW) 237 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW; 238 239 pr_err("Memory state around the buggy address:\n"); 240 241 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) { 242 const void *kaddr = kasan_shadow_to_mem(shadow_row); 243 char buffer[4 + (BITS_PER_LONG/8)*2]; 244 char shadow_buf[SHADOW_BYTES_PER_ROW]; 245 246 snprintf(buffer, sizeof(buffer), 247 (i == 0) ? ">%p: " : " %p: ", kaddr); 248 /* 249 * We should not pass a shadow pointer to generic 250 * function, because generic functions may try to 251 * access kasan mapping for the passed address. 252 */ 253 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW); 254 print_hex_dump(KERN_ERR, buffer, 255 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1, 256 shadow_buf, SHADOW_BYTES_PER_ROW, 0); 257 258 if (row_is_guilty(shadow_row, shadow)) 259 pr_err("%*c\n", 260 shadow_pointer_offset(shadow_row, shadow), 261 '^'); 262 263 shadow_row += SHADOW_BYTES_PER_ROW; 264 } 265 } 266 267 static void kasan_report_error(struct kasan_access_info *info) 268 { 269 unsigned long flags; 270 const char *bug_type; 271 272 kasan_start_report(&flags); 273 274 if (info->access_addr < 275 kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) { 276 if ((unsigned long)info->access_addr < PAGE_SIZE) 277 bug_type = "null-ptr-deref"; 278 else if ((unsigned long)info->access_addr < TASK_SIZE) 279 bug_type = "user-memory-access"; 280 else 281 bug_type = "wild-memory-access"; 282 pr_err("BUG: KASAN: %s on address %p\n", 283 bug_type, info->access_addr); 284 pr_err("%s of size %zu by task %s/%d\n", 285 info->is_write ? "Write" : "Read", 286 info->access_size, current->comm, 287 task_pid_nr(current)); 288 dump_stack(); 289 } else { 290 print_error_description(info); 291 print_address_description(info); 292 print_shadow_for_address(info->first_bad_addr); 293 } 294 295 kasan_end_report(&flags); 296 } 297 298 static unsigned long kasan_flags; 299 300 #define KASAN_BIT_REPORTED 0 301 #define KASAN_BIT_MULTI_SHOT 1 302 303 bool kasan_save_enable_multi_shot(void) 304 { 305 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 306 } 307 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot); 308 309 void kasan_restore_multi_shot(bool enabled) 310 { 311 if (!enabled) 312 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 313 } 314 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot); 315 316 static int __init kasan_set_multi_shot(char *str) 317 { 318 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 319 return 1; 320 } 321 __setup("kasan_multi_shot", kasan_set_multi_shot); 322 323 static inline bool kasan_report_enabled(void) 324 { 325 if (current->kasan_depth) 326 return false; 327 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) 328 return true; 329 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags); 330 } 331 332 void kasan_report(unsigned long addr, size_t size, 333 bool is_write, unsigned long ip) 334 { 335 struct kasan_access_info info; 336 337 if (likely(!kasan_report_enabled())) 338 return; 339 340 disable_trace_on_warning(); 341 342 info.access_addr = (void *)addr; 343 info.access_size = size; 344 info.is_write = is_write; 345 info.ip = ip; 346 347 kasan_report_error(&info); 348 } 349 350 351 #define DEFINE_ASAN_REPORT_LOAD(size) \ 352 void __asan_report_load##size##_noabort(unsigned long addr) \ 353 { \ 354 kasan_report(addr, size, false, _RET_IP_); \ 355 } \ 356 EXPORT_SYMBOL(__asan_report_load##size##_noabort) 357 358 #define DEFINE_ASAN_REPORT_STORE(size) \ 359 void __asan_report_store##size##_noabort(unsigned long addr) \ 360 { \ 361 kasan_report(addr, size, true, _RET_IP_); \ 362 } \ 363 EXPORT_SYMBOL(__asan_report_store##size##_noabort) 364 365 DEFINE_ASAN_REPORT_LOAD(1); 366 DEFINE_ASAN_REPORT_LOAD(2); 367 DEFINE_ASAN_REPORT_LOAD(4); 368 DEFINE_ASAN_REPORT_LOAD(8); 369 DEFINE_ASAN_REPORT_LOAD(16); 370 DEFINE_ASAN_REPORT_STORE(1); 371 DEFINE_ASAN_REPORT_STORE(2); 372 DEFINE_ASAN_REPORT_STORE(4); 373 DEFINE_ASAN_REPORT_STORE(8); 374 DEFINE_ASAN_REPORT_STORE(16); 375 376 void __asan_report_load_n_noabort(unsigned long addr, size_t size) 377 { 378 kasan_report(addr, size, false, _RET_IP_); 379 } 380 EXPORT_SYMBOL(__asan_report_load_n_noabort); 381 382 void __asan_report_store_n_noabort(unsigned long addr, size_t size) 383 { 384 kasan_report(addr, size, true, _RET_IP_); 385 } 386 EXPORT_SYMBOL(__asan_report_store_n_noabort); 387