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                         if (!p)
 132                                 return -ENOMEM;
 133
 134                         pmd_populate_kernel(&init_mm, pmd, p);
 135                 }
 136                 zero_pte_populate(pmd, addr, next);
 137         } while (pmd++, addr = next, addr != end);
 138
 139         return 0;
 140 }
 141
 142 static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
 143                                 unsigned long end)
 144 {
 145         pud_t *pud = pud_offset(p4d, addr);
 146         unsigned long next;
 147
 148         do {
 149                 next = pud_addr_end(addr, end);
 150                 if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
 151                         pmd_t *pmd;
 152
 153                         pud_populate(&init_mm, pud,
 154                                         lm_alias(kasan_early_shadow_pmd));
 155                         pmd = pmd_offset(pud, addr);
 156                         pmd_populate_kernel(&init_mm, pmd,
 157                                         lm_alias(kasan_early_shadow_pte));
 158                         continue;
 159                 }
 160
 161                 if (pud_none(*pud)) {
 162                         pmd_t *p;
 163
 164                         if (slab_is_available()) {
 165                                 p = pmd_alloc(&init_mm, pud, addr);
 166                                 if (!p)
 167                                         return -ENOMEM;
 168                         } else {
 169                                 pud_populate(&init_mm, pud,
 170                                         early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 171                         }
 172                 }
 173                 zero_pmd_populate(pud, addr, next);
 174         } while (pud++, addr = next, addr != end);
 175
 176         return 0;
 177 }
 178
 179 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
 180                                 unsigned long end)
 181 {
 182         p4d_t *p4d = p4d_offset(pgd, addr);
 183         unsigned long next;
 184
 185         do {
 186                 next = p4d_addr_end(addr, end);
 187                 if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
 188                         pud_t *pud;
 189                         pmd_t *pmd;
 190
 191                         p4d_populate(&init_mm, p4d,
 192                                         lm_alias(kasan_early_shadow_pud));
 193                         pud = pud_offset(p4d, addr);
 194                         pud_populate(&init_mm, pud,
 195                                         lm_alias(kasan_early_shadow_pmd));
 196                         pmd = pmd_offset(pud, addr);
 197                         pmd_populate_kernel(&init_mm, pmd,
 198                                         lm_alias(kasan_early_shadow_pte));
 199                         continue;
 200                 }
 201
 202                 if (p4d_none(*p4d)) {
 203                         pud_t *p;
 204
 205                         if (slab_is_available()) {
 206                                 p = pud_alloc(&init_mm, p4d, addr);
 207                                 if (!p)
 208                                         return -ENOMEM;
 209                         } else {
 210                                 p4d_populate(&init_mm, p4d,
 211                                         early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 212                         }
 213                 }
 214                 zero_pud_populate(p4d, addr, next);
 215         } while (p4d++, addr = next, addr != end);
 216
 217         return 0;
 218 }
 219
 220 /**
 221  * kasan_populate_early_shadow - populate shadow memory region with
 222  *                               kasan_early_shadow_page
 223  * @shadow_start: start of the memory range to populate
 224  * @shadow_end: end of the memory range to populate
 225  */
 226 int __ref kasan_populate_early_shadow(const void *shadow_start,
 227                                         const void *shadow_end)
 228 {
 229         unsigned long addr = (unsigned long)shadow_start;
 230         unsigned long end = (unsigned long)shadow_end;
 231         pgd_t *pgd = pgd_offset_k(addr);
 232         unsigned long next;
 233
 234         do {
 235                 next = pgd_addr_end(addr, end);
 236
 237                 if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
 238                         p4d_t *p4d;
 239                         pud_t *pud;
 240                         pmd_t *pmd;
 241
 242                         /*
 243                          * kasan_early_shadow_pud should be populated with pmds
 244                          * at this moment.
 245                          * [pud,pmd]_populate*() below needed only for
 246                          * 3,2 - level page tables where we don't have
 247                          * puds,pmds, so pgd_populate(), pud_populate()
 248                          * is noops.
 249                          */
 250                         pgd_populate(&init_mm, pgd,
 251                                         lm_alias(kasan_early_shadow_p4d));
 252                         p4d = p4d_offset(pgd, addr);
 253                         p4d_populate(&init_mm, p4d,
 254                                         lm_alias(kasan_early_shadow_pud));
 255                         pud = pud_offset(p4d, addr);
 256                         pud_populate(&init_mm, pud,
 257                                         lm_alias(kasan_early_shadow_pmd));
 258                         pmd = pmd_offset(pud, addr);
 259                         pmd_populate_kernel(&init_mm, pmd,
 260                                         lm_alias(kasan_early_shadow_pte));
 261                         continue;
 262                 }
 263
 264                 if (pgd_none(*pgd)) {
 265                         p4d_t *p;
 266
 267                         if (slab_is_available()) {
 268                                 p = p4d_alloc(&init_mm, pgd, addr);
 269                                 if (!p)
 270                                         return -ENOMEM;
 271                         } else {
 272                                 pgd_populate(&init_mm, pgd,
 273                                         early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 274                         }
 275                 }
 276                 zero_p4d_populate(pgd, addr, next);
 277         } while (pgd++, addr = next, addr != end);
 278
 279         return 0;
 280 }
 281
 282 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
 283 {
 284         pte_t *pte;
 285         int i;
 286
 287         for (i = 0; i < PTRS_PER_PTE; i++) {
 288                 pte = pte_start + i;
 289                 if (!pte_none(ptep_get(pte)))
 290                         return;
 291         }
 292
 293         pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
 294         pmd_clear(pmd);
 295 }
 296
 297 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
 298 {
 299         pmd_t *pmd;
 300         int i;
 301
 302         for (i = 0; i < PTRS_PER_PMD; i++) {
 303                 pmd = pmd_start + i;
 304                 if (!pmd_none(*pmd))
 305                         return;
 306         }
 307
 308         pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
 309         pud_clear(pud);
 310 }
 311
 312 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
 313 {
 314         pud_t *pud;
 315         int i;
 316
 317         for (i = 0; i < PTRS_PER_PUD; i++) {
 318                 pud = pud_start + i;
 319                 if (!pud_none(*pud))
 320                         return;
 321         }
 322
 323         pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
 324         p4d_clear(p4d);
 325 }
 326
 327 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
 328 {
 329         p4d_t *p4d;
 330         int i;
 331
 332         for (i = 0; i < PTRS_PER_P4D; i++) {
 333                 p4d = p4d_start + i;
 334                 if (!p4d_none(*p4d))
 335                         return;
 336         }
 337
 338         p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
 339         pgd_clear(pgd);
 340 }
 341
 342 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
 343                                 unsigned long end)
 344 {
 345         unsigned long next;
 346         pte_t ptent;
 347
 348         for (; addr < end; addr = next, pte++) {
 349                 next = (addr + PAGE_SIZE) & PAGE_MASK;
 350                 if (next > end)
 351                         next = end;
 352
 353                 ptent = ptep_get(pte);
 354
 355                 if (!pte_present(ptent))
 356                         continue;
 357
 358                 if (WARN_ON(!kasan_early_shadow_page_entry(ptent)))
 359                         continue;
 360                 pte_clear(&init_mm, addr, pte);
 361         }
 362 }
 363
 364 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
 365                                 unsigned long end)
 366 {
 367         unsigned long next;
 368
 369         for (; addr < end; addr = next, pmd++) {
 370                 pte_t *pte;
 371
 372                 next = pmd_addr_end(addr, end);
 373
 374                 if (!pmd_present(*pmd))
 375                         continue;
 376
 377                 if (kasan_pte_table(*pmd)) {
 378                         if (IS_ALIGNED(addr, PMD_SIZE) &&
 379                             IS_ALIGNED(next, PMD_SIZE)) {
 380                                 pmd_clear(pmd);
 381                                 continue;
 382                         }
 383                 }
 384                 pte = pte_offset_kernel(pmd, addr);
 385                 kasan_remove_pte_table(pte, addr, next);
 386                 kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
 387         }
 388 }
 389
 390 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
 391                                 unsigned long end)
 392 {
 393         unsigned long next;
 394
 395         for (; addr < end; addr = next, pud++) {
 396                 pmd_t *pmd, *pmd_base;
 397
 398                 next = pud_addr_end(addr, end);
 399
 400                 if (!pud_present(*pud))
 401                         continue;
 402
 403                 if (kasan_pmd_table(*pud)) {
 404                         if (IS_ALIGNED(addr, PUD_SIZE) &&
 405                             IS_ALIGNED(next, PUD_SIZE)) {
 406                                 pud_clear(pud);
 407                                 continue;
 408                         }
 409                 }
 410                 pmd = pmd_offset(pud, addr);
 411                 pmd_base = pmd_offset(pud, 0);
 412                 kasan_remove_pmd_table(pmd, addr, next);
 413                 kasan_free_pmd(pmd_base, pud);
 414         }
 415 }
 416
 417 static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
 418                                 unsigned long end)
 419 {
 420         unsigned long next;
 421
 422         for (; addr < end; addr = next, p4d++) {
 423                 pud_t *pud;
 424
 425                 next = p4d_addr_end(addr, end);
 426
 427                 if (!p4d_present(*p4d))
 428                         continue;
 429
 430                 if (kasan_pud_table(*p4d)) {
 431                         if (IS_ALIGNED(addr, P4D_SIZE) &&
 432                             IS_ALIGNED(next, P4D_SIZE)) {
 433                                 p4d_clear(p4d);
 434                                 continue;
 435                         }
 436                 }
 437                 pud = pud_offset(p4d, addr);
 438                 kasan_remove_pud_table(pud, addr, next);
 439                 kasan_free_pud(pud_offset(p4d, 0), p4d);
 440         }
 441 }
 442
 443 void kasan_remove_zero_shadow(void *start, unsigned long size)
 444 {
 445         unsigned long addr, end, next;
 446         pgd_t *pgd;
 447
 448         addr = (unsigned long)kasan_mem_to_shadow(start);
 449         end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
 450
 451         if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
 452             WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
 453                 return;
 454
 455         for (; addr < end; addr = next) {
 456                 p4d_t *p4d;
 457
 458                 next = pgd_addr_end(addr, end);
 459
 460                 pgd = pgd_offset_k(addr);
 461                 if (!pgd_present(*pgd))
 462                         continue;
 463
 464                 if (kasan_p4d_table(*pgd)) {
 465                         if (IS_ALIGNED(addr, PGDIR_SIZE) &&
 466                             IS_ALIGNED(next, PGDIR_SIZE)) {
 467                                 pgd_clear(pgd);
 468                                 continue;
 469                         }
 470                 }
 471
 472                 p4d = p4d_offset(pgd, addr);
 473                 kasan_remove_p4d_table(p4d, addr, next);
 474                 kasan_free_p4d(p4d_offset(pgd, 0), pgd);
 475         }
 476 }
 477
 478 int kasan_add_zero_shadow(void *start, unsigned long size)
 479 {
 480         int ret;
 481         void *shadow_start, *shadow_end;
 482
 483         shadow_start = kasan_mem_to_shadow(start);
 484         shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
 485
 486         if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
 487             WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
 488                 return -EINVAL;
 489
 490         ret = kasan_populate_early_shadow(shadow_start, shadow_end);
 491         if (ret)
 492                 kasan_remove_zero_shadow(start, size);
 493         return ret;
 494 }