1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This file contains KASAN runtime code that manages shadow memory for 4 * generic and software tag-based KASAN modes. 5 * 6 * Copyright (c) 2014 Samsung Electronics Co., Ltd. 7 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com> 8 * 9 * Some code borrowed from https://github.com/xairy/kasan-prototype by 10 * Andrey Konovalov <andreyknvl@gmail.com> 11 */ 12 13 #include <linux/init.h> 14 #include <linux/kasan.h> 15 #include <linux/kernel.h> 16 #include <linux/kfence.h> 17 #include <linux/kmemleak.h> 18 #include <linux/memory.h> 19 #include <linux/mm.h> 20 #include <linux/string.h> 21 #include <linux/types.h> 22 #include <linux/vmalloc.h> 23 24 #include <asm/cacheflush.h> 25 #include <asm/tlbflush.h> 26 27 #include "kasan.h" 28 29 bool __kasan_check_read(const volatile void *p, unsigned int size) 30 { 31 return kasan_check_range((unsigned long)p, size, false, _RET_IP_); 32 } 33 EXPORT_SYMBOL(__kasan_check_read); 34 35 bool __kasan_check_write(const volatile void *p, unsigned int size) 36 { 37 return kasan_check_range((unsigned long)p, size, true, _RET_IP_); 38 } 39 EXPORT_SYMBOL(__kasan_check_write); 40 41 #undef memset 42 void *memset(void *addr, int c, size_t len) 43 { 44 if (!kasan_check_range((unsigned long)addr, len, true, _RET_IP_)) 45 return NULL; 46 47 return __memset(addr, c, len); 48 } 49 50 #ifdef __HAVE_ARCH_MEMMOVE 51 #undef memmove 52 void *memmove(void *dest, const void *src, size_t len) 53 { 54 if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) || 55 !kasan_check_range((unsigned long)dest, len, true, _RET_IP_)) 56 return NULL; 57 58 return __memmove(dest, src, len); 59 } 60 #endif 61 62 #undef memcpy 63 void *memcpy(void *dest, const void *src, size_t len) 64 { 65 if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) || 66 !kasan_check_range((unsigned long)dest, len, true, _RET_IP_)) 67 return NULL; 68 69 return __memcpy(dest, src, len); 70 } 71 72 void kasan_poison(const void *addr, size_t size, u8 value, bool init) 73 { 74 void *shadow_start, *shadow_end; 75 76 /* 77 * Perform shadow offset calculation based on untagged address, as 78 * some of the callers (e.g. kasan_poison_object_data) pass tagged 79 * addresses to this function. 80 */ 81 addr = kasan_reset_tag(addr); 82 83 /* Skip KFENCE memory if called explicitly outside of sl*b. */ 84 if (is_kfence_address(addr)) 85 return; 86 87 if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) 88 return; 89 if (WARN_ON(size & KASAN_GRANULE_MASK)) 90 return; 91 92 shadow_start = kasan_mem_to_shadow(addr); 93 shadow_end = kasan_mem_to_shadow(addr + size); 94 95 __memset(shadow_start, value, shadow_end - shadow_start); 96 } 97 EXPORT_SYMBOL(kasan_poison); 98 99 #ifdef CONFIG_KASAN_GENERIC 100 void kasan_poison_last_granule(const void *addr, size_t size) 101 { 102 if (size & KASAN_GRANULE_MASK) { 103 u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size); 104 *shadow = size & KASAN_GRANULE_MASK; 105 } 106 } 107 #endif 108 109 void kasan_unpoison(const void *addr, size_t size, bool init) 110 { 111 u8 tag = get_tag(addr); 112 113 /* 114 * Perform shadow offset calculation based on untagged address, as 115 * some of the callers (e.g. kasan_unpoison_object_data) pass tagged 116 * addresses to this function. 117 */ 118 addr = kasan_reset_tag(addr); 119 120 /* 121 * Skip KFENCE memory if called explicitly outside of sl*b. Also note 122 * that calls to ksize(), where size is not a multiple of machine-word 123 * size, would otherwise poison the invalid portion of the word. 124 */ 125 if (is_kfence_address(addr)) 126 return; 127 128 if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) 129 return; 130 131 /* Unpoison all granules that cover the object. */ 132 kasan_poison(addr, round_up(size, KASAN_GRANULE_SIZE), tag, false); 133 134 /* Partially poison the last granule for the generic mode. */ 135 if (IS_ENABLED(CONFIG_KASAN_GENERIC)) 136 kasan_poison_last_granule(addr, size); 137 } 138 139 #ifdef CONFIG_MEMORY_HOTPLUG 140 static bool shadow_mapped(unsigned long addr) 141 { 142 pgd_t *pgd = pgd_offset_k(addr); 143 p4d_t *p4d; 144 pud_t *pud; 145 pmd_t *pmd; 146 pte_t *pte; 147 148 if (pgd_none(*pgd)) 149 return false; 150 p4d = p4d_offset(pgd, addr); 151 if (p4d_none(*p4d)) 152 return false; 153 pud = pud_offset(p4d, addr); 154 if (pud_none(*pud)) 155 return false; 156 157 /* 158 * We can't use pud_large() or pud_huge(), the first one is 159 * arch-specific, the last one depends on HUGETLB_PAGE. So let's abuse 160 * pud_bad(), if pud is bad then it's bad because it's huge. 161 */ 162 if (pud_bad(*pud)) 163 return true; 164 pmd = pmd_offset(pud, addr); 165 if (pmd_none(*pmd)) 166 return false; 167 168 if (pmd_bad(*pmd)) 169 return true; 170 pte = pte_offset_kernel(pmd, addr); 171 return !pte_none(*pte); 172 } 173 174 static int __meminit kasan_mem_notifier(struct notifier_block *nb, 175 unsigned long action, void *data) 176 { 177 struct memory_notify *mem_data = data; 178 unsigned long nr_shadow_pages, start_kaddr, shadow_start; 179 unsigned long shadow_end, shadow_size; 180 181 nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT; 182 start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn); 183 shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr); 184 shadow_size = nr_shadow_pages << PAGE_SHIFT; 185 shadow_end = shadow_start + shadow_size; 186 187 if (WARN_ON(mem_data->nr_pages % KASAN_GRANULE_SIZE) || 188 WARN_ON(start_kaddr % KASAN_MEMORY_PER_SHADOW_PAGE)) 189 return NOTIFY_BAD; 190 191 switch (action) { 192 case MEM_GOING_ONLINE: { 193 void *ret; 194 195 /* 196 * If shadow is mapped already than it must have been mapped 197 * during the boot. This could happen if we onlining previously 198 * offlined memory. 199 */ 200 if (shadow_mapped(shadow_start)) 201 return NOTIFY_OK; 202 203 ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start, 204 shadow_end, GFP_KERNEL, 205 PAGE_KERNEL, VM_NO_GUARD, 206 pfn_to_nid(mem_data->start_pfn), 207 __builtin_return_address(0)); 208 if (!ret) 209 return NOTIFY_BAD; 210 211 kmemleak_ignore(ret); 212 return NOTIFY_OK; 213 } 214 case MEM_CANCEL_ONLINE: 215 case MEM_OFFLINE: { 216 struct vm_struct *vm; 217 218 /* 219 * shadow_start was either mapped during boot by kasan_init() 220 * or during memory online by __vmalloc_node_range(). 221 * In the latter case we can use vfree() to free shadow. 222 * Non-NULL result of the find_vm_area() will tell us if 223 * that was the second case. 224 * 225 * Currently it's not possible to free shadow mapped 226 * during boot by kasan_init(). It's because the code 227 * to do that hasn't been written yet. So we'll just 228 * leak the memory. 229 */ 230 vm = find_vm_area((void *)shadow_start); 231 if (vm) 232 vfree((void *)shadow_start); 233 } 234 } 235 236 return NOTIFY_OK; 237 } 238 239 static int __init kasan_memhotplug_init(void) 240 { 241 hotplug_memory_notifier(kasan_mem_notifier, 0); 242 243 return 0; 244 } 245 246 core_initcall(kasan_memhotplug_init); 247 #endif 248 249 #ifdef CONFIG_KASAN_VMALLOC 250 251 static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr, 252 void *unused) 253 { 254 unsigned long page; 255 pte_t pte; 256 257 if (likely(!pte_none(*ptep))) 258 return 0; 259 260 page = __get_free_page(GFP_KERNEL); 261 if (!page) 262 return -ENOMEM; 263 264 memset((void *)page, KASAN_VMALLOC_INVALID, PAGE_SIZE); 265 pte = pfn_pte(PFN_DOWN(__pa(page)), PAGE_KERNEL); 266 267 spin_lock(&init_mm.page_table_lock); 268 if (likely(pte_none(*ptep))) { 269 set_pte_at(&init_mm, addr, ptep, pte); 270 page = 0; 271 } 272 spin_unlock(&init_mm.page_table_lock); 273 if (page) 274 free_page(page); 275 return 0; 276 } 277 278 int kasan_populate_vmalloc(unsigned long addr, unsigned long size) 279 { 280 unsigned long shadow_start, shadow_end; 281 int ret; 282 283 if (!is_vmalloc_or_module_addr((void *)addr)) 284 return 0; 285 286 shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr); 287 shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE); 288 shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size); 289 shadow_end = ALIGN(shadow_end, PAGE_SIZE); 290 291 ret = apply_to_page_range(&init_mm, shadow_start, 292 shadow_end - shadow_start, 293 kasan_populate_vmalloc_pte, NULL); 294 if (ret) 295 return ret; 296 297 flush_cache_vmap(shadow_start, shadow_end); 298 299 /* 300 * We need to be careful about inter-cpu effects here. Consider: 301 * 302 * CPU#0 CPU#1 303 * WRITE_ONCE(p, vmalloc(100)); while (x = READ_ONCE(p)) ; 304 * p[99] = 1; 305 * 306 * With compiler instrumentation, that ends up looking like this: 307 * 308 * CPU#0 CPU#1 309 * // vmalloc() allocates memory 310 * // let a = area->addr 311 * // we reach kasan_populate_vmalloc 312 * // and call kasan_unpoison: 313 * STORE shadow(a), unpoison_val 314 * ... 315 * STORE shadow(a+99), unpoison_val x = LOAD p 316 * // rest of vmalloc process <data dependency> 317 * STORE p, a LOAD shadow(x+99) 318 * 319 * If there is no barrier between the end of unpoisoning the shadow 320 * and the store of the result to p, the stores could be committed 321 * in a different order by CPU#0, and CPU#1 could erroneously observe 322 * poison in the shadow. 323 * 324 * We need some sort of barrier between the stores. 325 * 326 * In the vmalloc() case, this is provided by a smp_wmb() in 327 * clear_vm_uninitialized_flag(). In the per-cpu allocator and in 328 * get_vm_area() and friends, the caller gets shadow allocated but 329 * doesn't have any pages mapped into the virtual address space that 330 * has been reserved. Mapping those pages in will involve taking and 331 * releasing a page-table lock, which will provide the barrier. 332 */ 333 334 return 0; 335 } 336 337 /* 338 * Poison the shadow for a vmalloc region. Called as part of the 339 * freeing process at the time the region is freed. 340 */ 341 void kasan_poison_vmalloc(const void *start, unsigned long size) 342 { 343 if (!is_vmalloc_or_module_addr(start)) 344 return; 345 346 size = round_up(size, KASAN_GRANULE_SIZE); 347 kasan_poison(start, size, KASAN_VMALLOC_INVALID, false); 348 } 349 350 void kasan_unpoison_vmalloc(const void *start, unsigned long size) 351 { 352 if (!is_vmalloc_or_module_addr(start)) 353 return; 354 355 kasan_unpoison(start, size, false); 356 } 357 358 static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr, 359 void *unused) 360 { 361 unsigned long page; 362 363 page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT); 364 365 spin_lock(&init_mm.page_table_lock); 366 367 if (likely(!pte_none(*ptep))) { 368 pte_clear(&init_mm, addr, ptep); 369 free_page(page); 370 } 371 spin_unlock(&init_mm.page_table_lock); 372 373 return 0; 374 } 375 376 /* 377 * Release the backing for the vmalloc region [start, end), which 378 * lies within the free region [free_region_start, free_region_end). 379 * 380 * This can be run lazily, long after the region was freed. It runs 381 * under vmap_area_lock, so it's not safe to interact with the vmalloc/vmap 382 * infrastructure. 383 * 384 * How does this work? 385 * ------------------- 386 * 387 * We have a region that is page aligned, labeled as A. 388 * That might not map onto the shadow in a way that is page-aligned: 389 * 390 * start end 391 * v v 392 * |????????|????????|AAAAAAAA|AA....AA|AAAAAAAA|????????| < vmalloc 393 * -------- -------- -------- -------- -------- 394 * | | | | | 395 * | | | /-------/ | 396 * \-------\|/------/ |/---------------/ 397 * ||| || 398 * |??AAAAAA|AAAAAAAA|AA??????| < shadow 399 * (1) (2) (3) 400 * 401 * First we align the start upwards and the end downwards, so that the 402 * shadow of the region aligns with shadow page boundaries. In the 403 * example, this gives us the shadow page (2). This is the shadow entirely 404 * covered by this allocation. 405 * 406 * Then we have the tricky bits. We want to know if we can free the 407 * partially covered shadow pages - (1) and (3) in the example. For this, 408 * we are given the start and end of the free region that contains this 409 * allocation. Extending our previous example, we could have: 410 * 411 * free_region_start free_region_end 412 * | start end | 413 * v v v v 414 * |FFFFFFFF|FFFFFFFF|AAAAAAAA|AA....AA|AAAAAAAA|FFFFFFFF| < vmalloc 415 * -------- -------- -------- -------- -------- 416 * | | | | | 417 * | | | /-------/ | 418 * \-------\|/------/ |/---------------/ 419 * ||| || 420 * |FFAAAAAA|AAAAAAAA|AAF?????| < shadow 421 * (1) (2) (3) 422 * 423 * Once again, we align the start of the free region up, and the end of 424 * the free region down so that the shadow is page aligned. So we can free 425 * page (1) - we know no allocation currently uses anything in that page, 426 * because all of it is in the vmalloc free region. But we cannot free 427 * page (3), because we can't be sure that the rest of it is unused. 428 * 429 * We only consider pages that contain part of the original region for 430 * freeing: we don't try to free other pages from the free region or we'd 431 * end up trying to free huge chunks of virtual address space. 432 * 433 * Concurrency 434 * ----------- 435 * 436 * How do we know that we're not freeing a page that is simultaneously 437 * being used for a fresh allocation in kasan_populate_vmalloc(_pte)? 438 * 439 * We _can_ have kasan_release_vmalloc and kasan_populate_vmalloc running 440 * at the same time. While we run under free_vmap_area_lock, the population 441 * code does not. 442 * 443 * free_vmap_area_lock instead operates to ensure that the larger range 444 * [free_region_start, free_region_end) is safe: because __alloc_vmap_area and 445 * the per-cpu region-finding algorithm both run under free_vmap_area_lock, 446 * no space identified as free will become used while we are running. This 447 * means that so long as we are careful with alignment and only free shadow 448 * pages entirely covered by the free region, we will not run in to any 449 * trouble - any simultaneous allocations will be for disjoint regions. 450 */ 451 void kasan_release_vmalloc(unsigned long start, unsigned long end, 452 unsigned long free_region_start, 453 unsigned long free_region_end) 454 { 455 void *shadow_start, *shadow_end; 456 unsigned long region_start, region_end; 457 unsigned long size; 458 459 region_start = ALIGN(start, KASAN_MEMORY_PER_SHADOW_PAGE); 460 region_end = ALIGN_DOWN(end, KASAN_MEMORY_PER_SHADOW_PAGE); 461 462 free_region_start = ALIGN(free_region_start, KASAN_MEMORY_PER_SHADOW_PAGE); 463 464 if (start != region_start && 465 free_region_start < region_start) 466 region_start -= KASAN_MEMORY_PER_SHADOW_PAGE; 467 468 free_region_end = ALIGN_DOWN(free_region_end, KASAN_MEMORY_PER_SHADOW_PAGE); 469 470 if (end != region_end && 471 free_region_end > region_end) 472 region_end += KASAN_MEMORY_PER_SHADOW_PAGE; 473 474 shadow_start = kasan_mem_to_shadow((void *)region_start); 475 shadow_end = kasan_mem_to_shadow((void *)region_end); 476 477 if (shadow_end > shadow_start) { 478 size = shadow_end - shadow_start; 479 apply_to_existing_page_range(&init_mm, 480 (unsigned long)shadow_start, 481 size, kasan_depopulate_vmalloc_pte, 482 NULL); 483 flush_tlb_kernel_range((unsigned long)shadow_start, 484 (unsigned long)shadow_end); 485 } 486 } 487 488 #else /* CONFIG_KASAN_VMALLOC */ 489 490 int kasan_module_alloc(void *addr, size_t size) 491 { 492 void *ret; 493 size_t scaled_size; 494 size_t shadow_size; 495 unsigned long shadow_start; 496 497 shadow_start = (unsigned long)kasan_mem_to_shadow(addr); 498 scaled_size = (size + KASAN_GRANULE_SIZE - 1) >> 499 KASAN_SHADOW_SCALE_SHIFT; 500 shadow_size = round_up(scaled_size, PAGE_SIZE); 501 502 if (WARN_ON(!PAGE_ALIGNED(shadow_start))) 503 return -EINVAL; 504 505 ret = __vmalloc_node_range(shadow_size, 1, shadow_start, 506 shadow_start + shadow_size, 507 GFP_KERNEL, 508 PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE, 509 __builtin_return_address(0)); 510 511 if (ret) { 512 __memset(ret, KASAN_SHADOW_INIT, shadow_size); 513 find_vm_area(addr)->flags |= VM_KASAN; 514 kmemleak_ignore(ret); 515 return 0; 516 } 517 518 return -ENOMEM; 519 } 520 521 void kasan_free_shadow(const struct vm_struct *vm) 522 { 523 if (vm->flags & VM_KASAN) 524 vfree(kasan_mem_to_shadow(vm->addr)); 525 } 526 527 #endif 528