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