mm/kasan/init.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * This file contains some kasan initialization code.
   4  *
   5  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
   6  * Author: Andrey Ryabinin <[email protected]>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  */
  13
  14 #include <linux/memblock.h>
  15 #include <linux/init.h>
  16 #include <linux/kasan.h>
  17 #include <linux/kernel.h>
  18 #include <linux/mm.h>
  19 #include <linux/pfn.h>
  20 #include <linux/slab.h>
  21
  22 #include <asm/page.h>
  23 #include <asm/pgalloc.h>
  24
  25 #include "kasan.h"
  26
  27 /*
  28  * This page serves two purposes:
  29  *   - It used as early shadow memory. The entire shadow region populated
  30  *     with this page, before we will be able to setup normal shadow memory.
  31  *   - Latter it reused it as zero shadow to cover large ranges of memory
  32  *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
  33  */
  34 unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;
  35
  36 #if CONFIG_PGTABLE_LEVELS > 4
  37 p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
  38 static inline bool kasan_p4d_table(pgd_t pgd)
  39 {
  40         return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
  41 }
  42 #else
  43 static inline bool kasan_p4d_table(pgd_t pgd)
  44 {
  45         return 0;
  46 }
  47 #endif
  48 #if CONFIG_PGTABLE_LEVELS > 3
  49 pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
  50 static inline bool kasan_pud_table(p4d_t p4d)
  51 {
  52         return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
  53 }
  54 #else
  55 static inline bool kasan_pud_table(p4d_t p4d)
  56 {
  57         return 0;
  58 }
  59 #endif
  60 #if CONFIG_PGTABLE_LEVELS > 2
  61 pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
  62 static inline bool kasan_pmd_table(pud_t pud)
  63 {
  64         return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
  65 }
  66 #else
  67 static inline bool kasan_pmd_table(pud_t pud)
  68 {
  69         return 0;
  70 }
  71 #endif
  72 pte_t kasan_early_shadow_pte[PTRS_PER_PTE] __page_aligned_bss;
  73
  74 static inline bool kasan_pte_table(pmd_t pmd)
  75 {
  76         return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
  77 }
  78
  79 static inline bool kasan_early_shadow_page_entry(pte_t pte)
  80 {
  81         return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
  82 }
  83
  84 static __init void *early_alloc(size_t size, int node)
  85 {
  86         return memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
  87                                         MEMBLOCK_ALLOC_ACCESSIBLE, node);
  88 }
  89
  90 static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
  91                                 unsigned long end)
  92 {
  93         pte_t *pte = pte_offset_kernel(pmd, addr);
  94         pte_t zero_pte;
  95
  96         zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
  97                                 PAGE_KERNEL);
  98         zero_pte = pte_wrprotect(zero_pte);
  99
 100         while (addr + PAGE_SIZE <= end) {
 101                 set_pte_at(&init_mm, addr, pte, zero_pte);
 102                 addr += PAGE_SIZE;
 103                 pte = pte_offset_kernel(pmd, addr);
 104         }
 105 }
 106
 107 static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
 108                                 unsigned long end)
 109 {
 110         pmd_t *pmd = pmd_offset(pud, addr);
 111         unsigned long next;
 112
 113         do {
 114                 next = pmd_addr_end(addr, end);
 115
 116                 if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
 117                         pmd_populate_kernel(&init_mm, pmd,
 118                                         lm_alias(kasan_early_shadow_pte));
 119                         continue;
 120                 }
 121
 122                 if (pmd_none(*pmd)) {
 123                         pte_t *p;
 124
 125                         if (slab_is_available())
 126                                 p = pte_alloc_one_kernel(&init_mm);
 127                         else
 128                                 p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
 129                         if (!p)
 130                                 return -ENOMEM;
 131
 132                         pmd_populate_kernel(&init_mm, pmd, p);
 133                 }
 134                 zero_pte_populate(pmd, addr, next);
 135         } while (pmd++, addr = next, addr != end);
 136
 137         return 0;
 138 }
 139
 140 static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
 141                                 unsigned long end)
 142 {
 143         pud_t *pud = pud_offset(p4d, addr);
 144         unsigned long next;
 145
 146         do {
 147                 next = pud_addr_end(addr, end);
 148                 if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
 149                         pmd_t *pmd;
 150
 151                         pud_populate(&init_mm, pud,
 152                                         lm_alias(kasan_early_shadow_pmd));
 153                         pmd = pmd_offset(pud, addr);
 154                         pmd_populate_kernel(&init_mm, pmd,
 155                                         lm_alias(kasan_early_shadow_pte));
 156                         continue;
 157                 }
 158
 159                 if (pud_none(*pud)) {
 160                         pmd_t *p;
 161
 162                         if (slab_is_available()) {
 163                                 p = pmd_alloc(&init_mm, pud, addr);
 164                                 if (!p)
 165                                         return -ENOMEM;
 166                         } else {
 167                                 pud_populate(&init_mm, pud,
 168                                         early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 169                         }
 170                 }
 171                 zero_pmd_populate(pud, addr, next);
 172         } while (pud++, addr = next, addr != end);
 173
 174         return 0;
 175 }
 176
 177 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
 178                                 unsigned long end)
 179 {
 180         p4d_t *p4d = p4d_offset(pgd, addr);
 181         unsigned long next;
 182
 183         do {
 184                 next = p4d_addr_end(addr, end);
 185                 if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
 186                         pud_t *pud;
 187                         pmd_t *pmd;
 188
 189                         p4d_populate(&init_mm, p4d,
 190                                         lm_alias(kasan_early_shadow_pud));
 191                         pud = pud_offset(p4d, addr);
 192                         pud_populate(&init_mm, pud,
 193                                         lm_alias(kasan_early_shadow_pmd));
 194                         pmd = pmd_offset(pud, addr);
 195                         pmd_populate_kernel(&init_mm, pmd,
 196                                         lm_alias(kasan_early_shadow_pte));
 197                         continue;
 198                 }
 199
 200                 if (p4d_none(*p4d)) {
 201                         pud_t *p;
 202
 203                         if (slab_is_available()) {
 204                                 p = pud_alloc(&init_mm, p4d, addr);
 205                                 if (!p)
 206                                         return -ENOMEM;
 207                         } else {
 208                                 p4d_populate(&init_mm, p4d,
 209                                         early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 210                         }
 211                 }
 212                 zero_pud_populate(p4d, addr, next);
 213         } while (p4d++, addr = next, addr != end);
 214
 215         return 0;
 216 }
 217
 218 /**
 219  * kasan_populate_early_shadow - populate shadow memory region with
 220  *                               kasan_early_shadow_page
 221  * @shadow_start - start of the memory range to populate
 222  * @shadow_end   - end of the memory range to populate
 223  */
 224 int __ref kasan_populate_early_shadow(const void *shadow_start,
 225                                         const void *shadow_end)
 226 {
 227         unsigned long addr = (unsigned long)shadow_start;
 228         unsigned long end = (unsigned long)shadow_end;
 229         pgd_t *pgd = pgd_offset_k(addr);
 230         unsigned long next;
 231
 232         do {
 233                 next = pgd_addr_end(addr, end);
 234
 235                 if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
 236                         p4d_t *p4d;
 237                         pud_t *pud;
 238                         pmd_t *pmd;
 239
 240                         /*
 241                          * kasan_early_shadow_pud should be populated with pmds
 242                          * at this moment.
 243                          * [pud,pmd]_populate*() below needed only for
 244                          * 3,2 - level page tables where we don't have
 245                          * puds,pmds, so pgd_populate(), pud_populate()
 246                          * is noops.
 247                          *
 248                          * The ifndef is required to avoid build breakage.
 249                          *
 250                          * With 5level-fixup.h, pgd_populate() is not nop and
 251                          * we reference kasan_early_shadow_p4d. It's not defined
 252                          * unless 5-level paging enabled.
 253                          *
 254                          * The ifndef can be dropped once all KASAN-enabled
 255                          * architectures will switch to pgtable-nop4d.h.
 256                          */
 257 #ifndef __ARCH_HAS_5LEVEL_HACK
 258                         pgd_populate(&init_mm, pgd,
 259                                         lm_alias(kasan_early_shadow_p4d));
 260 #endif
 261                         p4d = p4d_offset(pgd, addr);
 262                         p4d_populate(&init_mm, p4d,
 263                                         lm_alias(kasan_early_shadow_pud));
 264                         pud = pud_offset(p4d, addr);
 265                         pud_populate(&init_mm, pud,
 266                                         lm_alias(kasan_early_shadow_pmd));
 267                         pmd = pmd_offset(pud, addr);
 268                         pmd_populate_kernel(&init_mm, pmd,
 269                                         lm_alias(kasan_early_shadow_pte));
 270                         continue;
 271                 }
 272
 273                 if (pgd_none(*pgd)) {
 274                         p4d_t *p;
 275
 276                         if (slab_is_available()) {
 277                                 p = p4d_alloc(&init_mm, pgd, addr);
 278                                 if (!p)
 279                                         return -ENOMEM;
 280                         } else {
 281                                 pgd_populate(&init_mm, pgd,
 282                                         early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 283                         }
 284                 }
 285                 zero_p4d_populate(pgd, addr, next);
 286         } while (pgd++, addr = next, addr != end);
 287
 288         return 0;
 289 }
 290
 291 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
 292 {
 293         pte_t *pte;
 294         int i;
 295
 296         for (i = 0; i < PTRS_PER_PTE; i++) {
 297                 pte = pte_start + i;
 298                 if (!pte_none(*pte))
 299                         return;
 300         }
 301
 302         pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
 303         pmd_clear(pmd);
 304 }
 305
 306 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
 307 {
 308         pmd_t *pmd;
 309         int i;
 310
 311         for (i = 0; i < PTRS_PER_PMD; i++) {
 312                 pmd = pmd_start + i;
 313                 if (!pmd_none(*pmd))
 314                         return;
 315         }
 316
 317         pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
 318         pud_clear(pud);
 319 }
 320
 321 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
 322 {
 323         pud_t *pud;
 324         int i;
 325
 326         for (i = 0; i < PTRS_PER_PUD; i++) {
 327                 pud = pud_start + i;
 328                 if (!pud_none(*pud))
 329                         return;
 330         }
 331
 332         pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
 333         p4d_clear(p4d);
 334 }
 335
 336 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
 337 {
 338         p4d_t *p4d;
 339         int i;
 340
 341         for (i = 0; i < PTRS_PER_P4D; i++) {
 342                 p4d = p4d_start + i;
 343                 if (!p4d_none(*p4d))
 344                         return;
 345         }
 346
 347         p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
 348         pgd_clear(pgd);
 349 }
 350
 351 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
 352                                 unsigned long end)
 353 {
 354         unsigned long next;
 355
 356         for (; addr < end; addr = next, pte++) {
 357                 next = (addr + PAGE_SIZE) & PAGE_MASK;
 358                 if (next > end)
 359                         next = end;
 360
 361                 if (!pte_present(*pte))
 362                         continue;
 363
 364                 if (WARN_ON(!kasan_early_shadow_page_entry(*pte)))
 365                         continue;
 366                 pte_clear(&init_mm, addr, pte);
 367         }
 368 }
 369
 370 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
 371                                 unsigned long end)
 372 {
 373         unsigned long next;
 374
 375         for (; addr < end; addr = next, pmd++) {
 376                 pte_t *pte;
 377
 378                 next = pmd_addr_end(addr, end);
 379
 380                 if (!pmd_present(*pmd))
 381                         continue;
 382
 383                 if (kasan_pte_table(*pmd)) {
 384                         if (IS_ALIGNED(addr, PMD_SIZE) &&
 385                             IS_ALIGNED(next, PMD_SIZE))
 386                                 pmd_clear(pmd);
 387                         continue;
 388                 }
 389                 pte = pte_offset_kernel(pmd, addr);
 390                 kasan_remove_pte_table(pte, addr, next);
 391                 kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
 392         }
 393 }
 394
 395 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
 396                                 unsigned long end)
 397 {
 398         unsigned long next;
 399
 400         for (; addr < end; addr = next, pud++) {
 401                 pmd_t *pmd, *pmd_base;
 402
 403                 next = pud_addr_end(addr, end);
 404
 405                 if (!pud_present(*pud))
 406                         continue;
 407
 408                 if (kasan_pmd_table(*pud)) {
 409                         if (IS_ALIGNED(addr, PUD_SIZE) &&
 410                             IS_ALIGNED(next, PUD_SIZE))
 411                                 pud_clear(pud);
 412                         continue;
 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                 pud = pud_offset(p4d, addr);
 441                 kasan_remove_pud_table(pud, addr, next);
 442                 kasan_free_pud(pud_offset(p4d, 0), p4d);
 443         }
 444 }
 445
 446 void kasan_remove_zero_shadow(void *start, unsigned long size)
 447 {
 448         unsigned long addr, end, next;
 449         pgd_t *pgd;
 450
 451         addr = (unsigned long)kasan_mem_to_shadow(start);
 452         end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
 453
 454         if (WARN_ON((unsigned long)start %
 455                         (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
 456             WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
 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                 p4d = p4d_offset(pgd, addr);
 476                 kasan_remove_p4d_table(p4d, addr, next);
 477                 kasan_free_p4d(p4d_offset(pgd, 0), pgd);
 478         }
 479 }
 480
 481 int kasan_add_zero_shadow(void *start, unsigned long size)
 482 {
 483         int ret;
 484         void *shadow_start, *shadow_end;
 485
 486         shadow_start = kasan_mem_to_shadow(start);
 487         shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
 488
 489         if (WARN_ON((unsigned long)start %
 490                         (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
 491             WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
 492                 return -EINVAL;
 493
 494         ret = kasan_populate_early_shadow(shadow_start, shadow_end);
 495         if (ret)
 496                 kasan_remove_zero_shadow(shadow_start,
 497                                         size >> KASAN_SHADOW_SCALE_SHIFT);
 498         return ret;
 499 }