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