mm/kasan/init.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * This file contains KASAN shadow initialization code.
   4  *
   5  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
   6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   7  */
   8
   9 #include <linux/memblock.h>
  10 #include <linux/init.h>
  11 #include <linux/kasan.h>
  12 #include <linux/kernel.h>
  13 #include <linux/mm.h>
  14 #include <linux/pfn.h>
  15 #include <linux/slab.h>
  16
  17 #include <asm/page.h>
  18 #include <asm/pgalloc.h>
  19
  20 #include "kasan.h"
  21
  22 /*
  23  * This page serves two purposes:
  24  *   - It used as early shadow memory. The entire shadow region populated
  25  *     with this page, before we will be able to setup normal shadow memory.
  26  *   - Latter it reused it as zero shadow to cover large ranges of memory
  27  *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
  28  */
  29 unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;
  30
  31 #if CONFIG_PGTABLE_LEVELS > 4
  32 p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
  33 static inline bool kasan_p4d_table(pgd_t pgd)
  34 {
  35         return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
  36 }
  37 #else
  38 static inline bool kasan_p4d_table(pgd_t pgd)
  39 {
  40         return false;
  41 }
  42 #endif
  43 #if CONFIG_PGTABLE_LEVELS > 3
  44 pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
  45 static inline bool kasan_pud_table(p4d_t p4d)
  46 {
  47         return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
  48 }
  49 #else
  50 static inline bool kasan_pud_table(p4d_t p4d)
  51 {
  52         return false;
  53 }
  54 #endif
  55 #if CONFIG_PGTABLE_LEVELS > 2
  56 pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
  57 static inline bool kasan_pmd_table(pud_t pud)
  58 {
  59         return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
  60 }
  61 #else
  62 static inline bool kasan_pmd_table(pud_t pud)
  63 {
  64         return false;
  65 }
  66 #endif
  67 pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS]
  68         __page_aligned_bss;
  69
  70 static inline bool kasan_pte_table(pmd_t pmd)
  71 {
  72         return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
  73 }
  74
  75 static inline bool kasan_early_shadow_page_entry(pte_t pte)
  76 {
  77         return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
  78 }
  79
  80 static __init void *early_alloc(size_t size, int node)
  81 {
  82         void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
  83                                            MEMBLOCK_ALLOC_ACCESSIBLE, node);
  84
  85         if (!ptr)
  86                 panic("%s: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
  87                       __func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));
  88
  89         return ptr;
  90 }
  91
  92 static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
  93                                 unsigned long end)
  94 {
  95         pte_t *pte = pte_offset_kernel(pmd, addr);
  96         pte_t zero_pte;
  97
  98         zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
  99                                 PAGE_KERNEL);
 100         zero_pte = pte_wrprotect(zero_pte);
 101
 102         while (addr + PAGE_SIZE <= end) {
 103                 set_pte_at(&init_mm, addr, pte, zero_pte);
 104                 addr += PAGE_SIZE;
 105                 pte = pte_offset_kernel(pmd, addr);
 106         }
 107 }
 108
 109 static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
 110                                 unsigned long end)
 111 {
 112         pmd_t *pmd = pmd_offset(pud, addr);
 113         unsigned long next;
 114
 115         do {
 116                 next = pmd_addr_end(addr, end);
 117
 118                 if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
 119                         pmd_populate_kernel(&init_mm, pmd,
 120                                         lm_alias(kasan_early_shadow_pte));
 121                         continue;
 122                 }
 123
 124                 if (pmd_none(*pmd)) {
 125                         pte_t *p;
 126
 127                         if (slab_is_available())
 128                                 p = pte_alloc_one_kernel(&init_mm);
 129                         else {
 130                                 p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
 131                                 kernel_pte_init(p);
 132                         }
 133                         if (!p)
 134                                 return -ENOMEM;
 135
 136                         pmd_populate_kernel(&init_mm, pmd, p);
 137                 }
 138                 zero_pte_populate(pmd, addr, next);
 139         } while (pmd++, addr = next, addr != end);
 140
 141         return 0;
 142 }
 143
 144 static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
 145                                 unsigned long end)
 146 {
 147         pud_t *pud = pud_offset(p4d, addr);
 148         unsigned long next;
 149
 150         do {
 151                 next = pud_addr_end(addr, end);
 152                 if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
 153                         pmd_t *pmd;
 154
 155                         pud_populate(&init_mm, pud,
 156                                         lm_alias(kasan_early_shadow_pmd));
 157                         pmd = pmd_offset(pud, addr);
 158                         pmd_populate_kernel(&init_mm, pmd,
 159                                         lm_alias(kasan_early_shadow_pte));
 160                         continue;
 161                 }
 162
 163                 if (pud_none(*pud)) {
 164                         pmd_t *p;
 165
 166                         if (slab_is_available()) {
 167                                 p = pmd_alloc(&init_mm, pud, addr);
 168                                 if (!p)
 169                                         return -ENOMEM;
 170                         } else {
 171                                 p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
 172                                 pmd_init(p);
 173                                 pud_populate(&init_mm, pud, p);
 174                         }
 175                 }
 176                 zero_pmd_populate(pud, addr, next);
 177         } while (pud++, addr = next, addr != end);
 178
 179         return 0;
 180 }
 181
 182 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
 183                                 unsigned long end)
 184 {
 185         p4d_t *p4d = p4d_offset(pgd, addr);
 186         unsigned long next;
 187
 188         do {
 189                 next = p4d_addr_end(addr, end);
 190                 if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
 191                         pud_t *pud;
 192                         pmd_t *pmd;
 193
 194                         p4d_populate(&init_mm, p4d,
 195                                         lm_alias(kasan_early_shadow_pud));
 196                         pud = pud_offset(p4d, addr);
 197                         pud_populate(&init_mm, pud,
 198                                         lm_alias(kasan_early_shadow_pmd));
 199                         pmd = pmd_offset(pud, addr);
 200                         pmd_populate_kernel(&init_mm, pmd,
 201                                         lm_alias(kasan_early_shadow_pte));
 202                         continue;
 203                 }
 204
 205                 if (p4d_none(*p4d)) {
 206                         pud_t *p;
 207
 208                         if (slab_is_available()) {
 209                                 p = pud_alloc(&init_mm, p4d, addr);
 210                                 if (!p)
 211                                         return -ENOMEM;
 212                         } else {
 213                                 p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
 214                                 pud_init(p);
 215                                 p4d_populate(&init_mm, p4d, p);
 216                         }
 217                 }
 218                 zero_pud_populate(p4d, addr, next);
 219         } while (p4d++, addr = next, addr != end);
 220
 221         return 0;
 222 }
 223
 224 /**
 225  * kasan_populate_early_shadow - populate shadow memory region with
 226  *                               kasan_early_shadow_page
 227  * @shadow_start: start of the memory range to populate
 228  * @shadow_end: end of the memory range to populate
 229  */
 230 int __ref kasan_populate_early_shadow(const void *shadow_start,
 231                                         const void *shadow_end)
 232 {
 233         unsigned long addr = (unsigned long)shadow_start;
 234         unsigned long end = (unsigned long)shadow_end;
 235         pgd_t *pgd = pgd_offset_k(addr);
 236         unsigned long next;
 237
 238         do {
 239                 next = pgd_addr_end(addr, end);
 240
 241                 if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
 242                         p4d_t *p4d;
 243                         pud_t *pud;
 244                         pmd_t *pmd;
 245
 246                         /*
 247                          * kasan_early_shadow_pud should be populated with pmds
 248                          * at this moment.
 249                          * [pud,pmd]_populate*() below needed only for
 250                          * 3,2 - level page tables where we don't have
 251                          * puds,pmds, so pgd_populate(), pud_populate()
 252                          * is noops.
 253                          */
 254                         pgd_populate(&init_mm, pgd,
 255                                         lm_alias(kasan_early_shadow_p4d));
 256                         p4d = p4d_offset(pgd, addr);
 257                         p4d_populate(&init_mm, p4d,
 258                                         lm_alias(kasan_early_shadow_pud));
 259                         pud = pud_offset(p4d, addr);
 260                         pud_populate(&init_mm, pud,
 261                                         lm_alias(kasan_early_shadow_pmd));
 262                         pmd = pmd_offset(pud, addr);
 263                         pmd_populate_kernel(&init_mm, pmd,
 264                                         lm_alias(kasan_early_shadow_pte));
 265                         continue;
 266                 }
 267
 268                 if (pgd_none(*pgd)) {
 269                         p4d_t *p;
 270
 271                         if (slab_is_available()) {
 272                                 p = p4d_alloc(&init_mm, pgd, addr);
 273                                 if (!p)
 274                                         return -ENOMEM;
 275                         } else {
 276                                 pgd_populate(&init_mm, pgd,
 277                                         early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 278                         }
 279                 }
 280                 zero_p4d_populate(pgd, addr, next);
 281         } while (pgd++, addr = next, addr != end);
 282
 283         return 0;
 284 }
 285
 286 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
 287 {
 288         pte_t *pte;
 289         int i;
 290
 291         for (i = 0; i < PTRS_PER_PTE; i++) {
 292                 pte = pte_start + i;
 293                 if (!pte_none(ptep_get(pte)))
 294                         return;
 295         }
 296
 297         pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
 298         pmd_clear(pmd);
 299 }
 300
 301 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
 302 {
 303         pmd_t *pmd;
 304         int i;
 305
 306         for (i = 0; i < PTRS_PER_PMD; i++) {
 307                 pmd = pmd_start + i;
 308                 if (!pmd_none(*pmd))
 309                         return;
 310         }
 311
 312         pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
 313         pud_clear(pud);
 314 }
 315
 316 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
 317 {
 318         pud_t *pud;
 319         int i;
 320
 321         for (i = 0; i < PTRS_PER_PUD; i++) {
 322                 pud = pud_start + i;
 323                 if (!pud_none(*pud))
 324                         return;
 325         }
 326
 327         pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
 328         p4d_clear(p4d);
 329 }
 330
 331 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
 332 {
 333         p4d_t *p4d;
 334         int i;
 335
 336         for (i = 0; i < PTRS_PER_P4D; i++) {
 337                 p4d = p4d_start + i;
 338                 if (!p4d_none(*p4d))
 339                         return;
 340         }
 341
 342         p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
 343         pgd_clear(pgd);
 344 }
 345
 346 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
 347                                 unsigned long end)
 348 {
 349         unsigned long next;
 350         pte_t ptent;
 351
 352         for (; addr < end; addr = next, pte++) {
 353                 next = (addr + PAGE_SIZE) & PAGE_MASK;
 354                 if (next > end)
 355                         next = end;
 356
 357                 ptent = ptep_get(pte);
 358
 359                 if (!pte_present(ptent))
 360                         continue;
 361
 362                 if (WARN_ON(!kasan_early_shadow_page_entry(ptent)))
 363                         continue;
 364                 pte_clear(&init_mm, addr, pte);
 365         }
 366 }
 367
 368 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
 369                                 unsigned long end)
 370 {
 371         unsigned long next;
 372
 373         for (; addr < end; addr = next, pmd++) {
 374                 pte_t *pte;
 375
 376                 next = pmd_addr_end(addr, end);
 377
 378                 if (!pmd_present(*pmd))
 379                         continue;
 380
 381                 if (kasan_pte_table(*pmd)) {
 382                         if (IS_ALIGNED(addr, PMD_SIZE) &&
 383                             IS_ALIGNED(next, PMD_SIZE)) {
 384                                 pmd_clear(pmd);
 385                                 continue;
 386                         }
 387                 }
 388                 pte = pte_offset_kernel(pmd, addr);
 389                 kasan_remove_pte_table(pte, addr, next);
 390                 kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
 391         }
 392 }
 393
 394 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
 395                                 unsigned long end)
 396 {
 397         unsigned long next;
 398
 399         for (; addr < end; addr = next, pud++) {
 400                 pmd_t *pmd, *pmd_base;
 401
 402                 next = pud_addr_end(addr, end);
 403
 404                 if (!pud_present(*pud))
 405                         continue;
 406
 407                 if (kasan_pmd_table(*pud)) {
 408                         if (IS_ALIGNED(addr, PUD_SIZE) &&
 409                             IS_ALIGNED(next, PUD_SIZE)) {
 410                                 pud_clear(pud);
 411                                 continue;
 412                         }
 413                 }
 414                 pmd = pmd_offset(pud, addr);
 415                 pmd_base = pmd_offset(pud, 0);
 416                 kasan_remove_pmd_table(pmd, addr, next);
 417                 kasan_free_pmd(pmd_base, pud);
 418         }
 419 }
 420
 421 static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
 422                                 unsigned long end)
 423 {
 424         unsigned long next;
 425
 426         for (; addr < end; addr = next, p4d++) {
 427                 pud_t *pud;
 428
 429                 next = p4d_addr_end(addr, end);
 430
 431                 if (!p4d_present(*p4d))
 432                         continue;
 433
 434                 if (kasan_pud_table(*p4d)) {
 435                         if (IS_ALIGNED(addr, P4D_SIZE) &&
 436                             IS_ALIGNED(next, P4D_SIZE)) {
 437                                 p4d_clear(p4d);
 438                                 continue;
 439                         }
 440                 }
 441                 pud = pud_offset(p4d, addr);
 442                 kasan_remove_pud_table(pud, addr, next);
 443                 kasan_free_pud(pud_offset(p4d, 0), p4d);
 444         }
 445 }
 446
 447 void kasan_remove_zero_shadow(void *start, unsigned long size)
 448 {
 449         unsigned long addr, end, next;
 450         pgd_t *pgd;
 451
 452         addr = (unsigned long)kasan_mem_to_shadow(start);
 453         end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
 454
 455         if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
 456             WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
 457                 return;
 458
 459         for (; addr < end; addr = next) {
 460                 p4d_t *p4d;
 461
 462                 next = pgd_addr_end(addr, end);
 463
 464                 pgd = pgd_offset_k(addr);
 465                 if (!pgd_present(*pgd))
 466                         continue;
 467
 468                 if (kasan_p4d_table(*pgd)) {
 469                         if (IS_ALIGNED(addr, PGDIR_SIZE) &&
 470                             IS_ALIGNED(next, PGDIR_SIZE)) {
 471                                 pgd_clear(pgd);
 472                                 continue;
 473                         }
 474                 }
 475
 476                 p4d = p4d_offset(pgd, addr);
 477                 kasan_remove_p4d_table(p4d, addr, next);
 478                 kasan_free_p4d(p4d_offset(pgd, 0), pgd);
 479         }
 480 }
 481
 482 int kasan_add_zero_shadow(void *start, unsigned long size)
 483 {
 484         int ret;
 485         void *shadow_start, *shadow_end;
 486
 487         shadow_start = kasan_mem_to_shadow(start);
 488         shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
 489
 490         if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
 491             WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
 492                 return -EINVAL;
 493
 494         ret = kasan_populate_early_shadow(shadow_start, shadow_end);
 495         if (ret)
 496                 kasan_remove_zero_shadow(start, size);
 497         return ret;
 498 }