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