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