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