1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This file contains common generic and tag-based KASAN error reporting code. 4 * 5 * Copyright (c) 2014 Samsung Electronics Co., Ltd. 6 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com> 7 * 8 * Some code borrowed from https://github.com/xairy/kasan-prototype by 9 * Andrey Konovalov <andreyknvl@gmail.com> 10 * 11 * This program is free software; you can redistribute it and/or modify 12 * it under the terms of the GNU General Public License version 2 as 13 * published by the Free Software Foundation. 14 * 15 */ 16 17 #include <linux/bitops.h> 18 #include <linux/ftrace.h> 19 #include <linux/init.h> 20 #include <linux/kernel.h> 21 #include <linux/mm.h> 22 #include <linux/printk.h> 23 #include <linux/sched.h> 24 #include <linux/slab.h> 25 #include <linux/stackdepot.h> 26 #include <linux/stacktrace.h> 27 #include <linux/string.h> 28 #include <linux/types.h> 29 #include <linux/kasan.h> 30 #include <linux/module.h> 31 32 #include <asm/sections.h> 33 34 #include "kasan.h" 35 #include "../slab.h" 36 37 /* Shadow layout customization. */ 38 #define SHADOW_BYTES_PER_BLOCK 1 39 #define SHADOW_BLOCKS_PER_ROW 16 40 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK) 41 #define SHADOW_ROWS_AROUND_ADDR 2 42 43 static unsigned long kasan_flags; 44 45 #define KASAN_BIT_REPORTED 0 46 #define KASAN_BIT_MULTI_SHOT 1 47 48 bool kasan_save_enable_multi_shot(void) 49 { 50 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 51 } 52 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot); 53 54 void kasan_restore_multi_shot(bool enabled) 55 { 56 if (!enabled) 57 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 58 } 59 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot); 60 61 static int __init kasan_set_multi_shot(char *str) 62 { 63 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 64 return 1; 65 } 66 __setup("kasan_multi_shot", kasan_set_multi_shot); 67 68 static void print_error_description(struct kasan_access_info *info) 69 { 70 pr_err("BUG: KASAN: %s in %pS\n", 71 get_bug_type(info), (void *)info->ip); 72 pr_err("%s of size %zu at addr %px by task %s/%d\n", 73 info->is_write ? "Write" : "Read", info->access_size, 74 info->access_addr, current->comm, task_pid_nr(current)); 75 } 76 77 static DEFINE_SPINLOCK(report_lock); 78 79 static void start_report(unsigned long *flags) 80 { 81 /* 82 * Make sure we don't end up in loop. 83 */ 84 kasan_disable_current(); 85 spin_lock_irqsave(&report_lock, *flags); 86 pr_err("==================================================================\n"); 87 } 88 89 static void end_report(unsigned long *flags) 90 { 91 pr_err("==================================================================\n"); 92 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); 93 spin_unlock_irqrestore(&report_lock, *flags); 94 if (panic_on_warn) 95 panic("panic_on_warn set ...\n"); 96 kasan_enable_current(); 97 } 98 99 static void print_track(struct kasan_track *track, const char *prefix) 100 { 101 pr_err("%s by task %u:\n", prefix, track->pid); 102 if (track->stack) { 103 unsigned long *entries; 104 unsigned int nr_entries; 105 106 nr_entries = stack_depot_fetch(track->stack, &entries); 107 stack_trace_print(entries, nr_entries, 0); 108 } else { 109 pr_err("(stack is not available)\n"); 110 } 111 } 112 113 static struct page *addr_to_page(const void *addr) 114 { 115 if ((addr >= (void *)PAGE_OFFSET) && 116 (addr < high_memory)) 117 return virt_to_head_page(addr); 118 return NULL; 119 } 120 121 static void describe_object_addr(struct kmem_cache *cache, void *object, 122 const void *addr) 123 { 124 unsigned long access_addr = (unsigned long)addr; 125 unsigned long object_addr = (unsigned long)object; 126 const char *rel_type; 127 int rel_bytes; 128 129 pr_err("The buggy address belongs to the object at %px\n" 130 " which belongs to the cache %s of size %d\n", 131 object, cache->name, cache->object_size); 132 133 if (!addr) 134 return; 135 136 if (access_addr < object_addr) { 137 rel_type = "to the left"; 138 rel_bytes = object_addr - access_addr; 139 } else if (access_addr >= object_addr + cache->object_size) { 140 rel_type = "to the right"; 141 rel_bytes = access_addr - (object_addr + cache->object_size); 142 } else { 143 rel_type = "inside"; 144 rel_bytes = access_addr - object_addr; 145 } 146 147 pr_err("The buggy address is located %d bytes %s of\n" 148 " %d-byte region [%px, %px)\n", 149 rel_bytes, rel_type, cache->object_size, (void *)object_addr, 150 (void *)(object_addr + cache->object_size)); 151 } 152 153 static void describe_object(struct kmem_cache *cache, void *object, 154 const void *addr) 155 { 156 struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object); 157 158 if (cache->flags & SLAB_KASAN) { 159 print_track(&alloc_info->alloc_track, "Allocated"); 160 pr_err("\n"); 161 print_track(&alloc_info->free_track, "Freed"); 162 pr_err("\n"); 163 } 164 165 describe_object_addr(cache, object, addr); 166 } 167 168 static inline bool kernel_or_module_addr(const void *addr) 169 { 170 if (addr >= (void *)_stext && addr < (void *)_end) 171 return true; 172 if (is_module_address((unsigned long)addr)) 173 return true; 174 return false; 175 } 176 177 static inline bool init_task_stack_addr(const void *addr) 178 { 179 return addr >= (void *)&init_thread_union.stack && 180 (addr <= (void *)&init_thread_union.stack + 181 sizeof(init_thread_union.stack)); 182 } 183 184 static void print_address_description(void *addr) 185 { 186 struct page *page = addr_to_page(addr); 187 188 dump_stack(); 189 pr_err("\n"); 190 191 if (page && PageSlab(page)) { 192 struct kmem_cache *cache = page->slab_cache; 193 void *object = nearest_obj(cache, page, addr); 194 195 describe_object(cache, object, addr); 196 } 197 198 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) { 199 pr_err("The buggy address belongs to the variable:\n"); 200 pr_err(" %pS\n", addr); 201 } 202 203 if (page) { 204 pr_err("The buggy address belongs to the page:\n"); 205 dump_page(page, "kasan: bad access detected"); 206 } 207 } 208 209 static bool row_is_guilty(const void *row, const void *guilty) 210 { 211 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW); 212 } 213 214 static int shadow_pointer_offset(const void *row, const void *shadow) 215 { 216 /* The length of ">ff00ff00ff00ff00: " is 217 * 3 + (BITS_PER_LONG/8)*2 chars. 218 */ 219 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 + 220 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1; 221 } 222 223 static void print_shadow_for_address(const void *addr) 224 { 225 int i; 226 const void *shadow = kasan_mem_to_shadow(addr); 227 const void *shadow_row; 228 229 shadow_row = (void *)round_down((unsigned long)shadow, 230 SHADOW_BYTES_PER_ROW) 231 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW; 232 233 pr_err("Memory state around the buggy address:\n"); 234 235 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) { 236 const void *kaddr = kasan_shadow_to_mem(shadow_row); 237 char buffer[4 + (BITS_PER_LONG/8)*2]; 238 char shadow_buf[SHADOW_BYTES_PER_ROW]; 239 240 snprintf(buffer, sizeof(buffer), 241 (i == 0) ? ">%px: " : " %px: ", kaddr); 242 /* 243 * We should not pass a shadow pointer to generic 244 * function, because generic functions may try to 245 * access kasan mapping for the passed address. 246 */ 247 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW); 248 print_hex_dump(KERN_ERR, buffer, 249 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1, 250 shadow_buf, SHADOW_BYTES_PER_ROW, 0); 251 252 if (row_is_guilty(shadow_row, shadow)) 253 pr_err("%*c\n", 254 shadow_pointer_offset(shadow_row, shadow), 255 '^'); 256 257 shadow_row += SHADOW_BYTES_PER_ROW; 258 } 259 } 260 261 static bool report_enabled(void) 262 { 263 if (current->kasan_depth) 264 return false; 265 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) 266 return true; 267 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags); 268 } 269 270 void kasan_report_invalid_free(void *object, unsigned long ip) 271 { 272 unsigned long flags; 273 274 start_report(&flags); 275 pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip); 276 print_tags(get_tag(object), reset_tag(object)); 277 object = reset_tag(object); 278 pr_err("\n"); 279 print_address_description(object); 280 pr_err("\n"); 281 print_shadow_for_address(object); 282 end_report(&flags); 283 } 284 285 void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) 286 { 287 struct kasan_access_info info; 288 void *tagged_addr; 289 void *untagged_addr; 290 unsigned long flags; 291 292 if (likely(!report_enabled())) 293 return; 294 295 disable_trace_on_warning(); 296 297 tagged_addr = (void *)addr; 298 untagged_addr = reset_tag(tagged_addr); 299 300 info.access_addr = tagged_addr; 301 if (addr_has_shadow(untagged_addr)) 302 info.first_bad_addr = find_first_bad_addr(tagged_addr, size); 303 else 304 info.first_bad_addr = untagged_addr; 305 info.access_size = size; 306 info.is_write = is_write; 307 info.ip = ip; 308 309 start_report(&flags); 310 311 print_error_description(&info); 312 if (addr_has_shadow(untagged_addr)) 313 print_tags(get_tag(tagged_addr), info.first_bad_addr); 314 pr_err("\n"); 315 316 if (addr_has_shadow(untagged_addr)) { 317 print_address_description(untagged_addr); 318 pr_err("\n"); 319 print_shadow_for_address(info.first_bad_addr); 320 } else { 321 dump_stack(); 322 } 323 324 end_report(&flags); 325 } 326