mm/kasan/common.c

   1 /*
   2  * This file contains common generic and tag-based KASAN code.
   3  *
   4  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
   5  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   6  *
   7  * Some code borrowed from https://github.com/xairy/kasan-prototype by
   8  *        Andrey Konovalov <andreyknvl@gmail.com>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License version 2 as
  12  * published by the Free Software Foundation.
  13  *
  14  */
  15
  16 #include <linux/export.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/init.h>
  19 #include <linux/kasan.h>
  20 #include <linux/kernel.h>
  21 #include <linux/kmemleak.h>
  22 #include <linux/linkage.h>
  23 #include <linux/memblock.h>
  24 #include <linux/memory.h>
  25 #include <linux/mm.h>
  26 #include <linux/module.h>
  27 #include <linux/printk.h>
  28 #include <linux/sched.h>
  29 #include <linux/sched/task_stack.h>
  30 #include <linux/slab.h>
  31 #include <linux/stacktrace.h>
  32 #include <linux/string.h>
  33 #include <linux/types.h>
  34 #include <linux/vmalloc.h>
  35 #include <linux/bug.h>
  36
  37 #include "kasan.h"
  38 #include "../slab.h"
  39
  40 static inline int in_irqentry_text(unsigned long ptr)
  41 {
  42         return (ptr >= (unsigned long)&__irqentry_text_start &&
  43                 ptr < (unsigned long)&__irqentry_text_end) ||
  44                 (ptr >= (unsigned long)&__softirqentry_text_start &&
  45                  ptr < (unsigned long)&__softirqentry_text_end);
  46 }
  47
  48 static inline void filter_irq_stacks(struct stack_trace *trace)
  49 {
  50         int i;
  51
  52         if (!trace->nr_entries)
  53                 return;
  54         for (i = 0; i < trace->nr_entries; i++)
  55                 if (in_irqentry_text(trace->entries[i])) {
  56                         /* Include the irqentry function into the stack. */
  57                         trace->nr_entries = i + 1;
  58                         break;
  59                 }
  60 }
  61
  62 static inline depot_stack_handle_t save_stack(gfp_t flags)
  63 {
  64         unsigned long entries[KASAN_STACK_DEPTH];
  65         struct stack_trace trace = {
  66                 .nr_entries = 0,
  67                 .entries = entries,
  68                 .max_entries = KASAN_STACK_DEPTH,
  69                 .skip = 0
  70         };
  71
  72         save_stack_trace(&trace);
  73         filter_irq_stacks(&trace);
  74         if (trace.nr_entries != 0 &&
  75             trace.entries[trace.nr_entries-1] == ULONG_MAX)
  76                 trace.nr_entries--;
  77
  78         return depot_save_stack(&trace, flags);
  79 }
  80
  81 static inline void set_track(struct kasan_track *track, gfp_t flags)
  82 {
  83         track->pid = current->pid;
  84         track->stack = save_stack(flags);
  85 }
  86
  87 void kasan_enable_current(void)
  88 {
  89         current->kasan_depth++;
  90 }
  91
  92 void kasan_disable_current(void)
  93 {
  94         current->kasan_depth--;
  95 }
  96
  97 void kasan_check_read(const volatile void *p, unsigned int size)
  98 {
  99         check_memory_region((unsigned long)p, size, false, _RET_IP_);
 100 }
 101 EXPORT_SYMBOL(kasan_check_read);
 102
 103 void kasan_check_write(const volatile void *p, unsigned int size)
 104 {
 105         check_memory_region((unsigned long)p, size, true, _RET_IP_);
 106 }
 107 EXPORT_SYMBOL(kasan_check_write);
 108
 109 #undef memset
 110 void *memset(void *addr, int c, size_t len)
 111 {
 112         check_memory_region((unsigned long)addr, len, true, _RET_IP_);
 113
 114         return __memset(addr, c, len);
 115 }
 116
 117 #undef memmove
 118 void *memmove(void *dest, const void *src, size_t len)
 119 {
 120         check_memory_region((unsigned long)src, len, false, _RET_IP_);
 121         check_memory_region((unsigned long)dest, len, true, _RET_IP_);
 122
 123         return __memmove(dest, src, len);
 124 }
 125
 126 #undef memcpy
 127 void *memcpy(void *dest, const void *src, size_t len)
 128 {
 129         check_memory_region((unsigned long)src, len, false, _RET_IP_);
 130         check_memory_region((unsigned long)dest, len, true, _RET_IP_);
 131
 132         return __memcpy(dest, src, len);
 133 }
 134
 135 /*
 136  * Poisons the shadow memory for 'size' bytes starting from 'addr'.
 137  * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
 138  */
 139 void kasan_poison_shadow(const void *address, size_t size, u8 value)
 140 {
 141         void *shadow_start, *shadow_end;
 142
 143         shadow_start = kasan_mem_to_shadow(address);
 144         shadow_end = kasan_mem_to_shadow(address + size);
 145
 146         __memset(shadow_start, value, shadow_end - shadow_start);
 147 }
 148
 149 void kasan_unpoison_shadow(const void *address, size_t size)
 150 {
 151         kasan_poison_shadow(address, size, 0);
 152
 153         if (size & KASAN_SHADOW_MASK) {
 154                 u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
 155                 *shadow = size & KASAN_SHADOW_MASK;
 156         }
 157 }
 158
 159 static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
 160 {
 161         void *base = task_stack_page(task);
 162         size_t size = sp - base;
 163
 164         kasan_unpoison_shadow(base, size);
 165 }
 166
 167 /* Unpoison the entire stack for a task. */
 168 void kasan_unpoison_task_stack(struct task_struct *task)
 169 {
 170         __kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE);
 171 }
 172
 173 /* Unpoison the stack for the current task beyond a watermark sp value. */
 174 asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
 175 {
 176         /*
 177          * Calculate the task stack base address.  Avoid using 'current'
 178          * because this function is called by early resume code which hasn't
 179          * yet set up the percpu register (%gs).
 180          */
 181         void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));
 182
 183         kasan_unpoison_shadow(base, watermark - base);
 184 }
 185
 186 /*
 187  * Clear all poison for the region between the current SP and a provided
 188  * watermark value, as is sometimes required prior to hand-crafted asm function
 189  * returns in the middle of functions.
 190  */
 191 void kasan_unpoison_stack_above_sp_to(const void *watermark)
 192 {
 193         const void *sp = __builtin_frame_address(0);
 194         size_t size = watermark - sp;
 195
 196         if (WARN_ON(sp > watermark))
 197                 return;
 198         kasan_unpoison_shadow(sp, size);
 199 }
 200
 201 void kasan_alloc_pages(struct page *page, unsigned int order)
 202 {
 203         if (likely(!PageHighMem(page)))
 204                 kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 205 }
 206
 207 void kasan_free_pages(struct page *page, unsigned int order)
 208 {
 209         if (likely(!PageHighMem(page)))
 210                 kasan_poison_shadow(page_address(page),
 211                                 PAGE_SIZE << order,
 212                                 KASAN_FREE_PAGE);
 213 }
 214
 215 /*
 216  * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
 217  * For larger allocations larger redzones are used.
 218  */
 219 static inline unsigned int optimal_redzone(unsigned int object_size)
 220 {
 221         return
 222                 object_size <= 64        - 16   ? 16 :
 223                 object_size <= 128       - 32   ? 32 :
 224                 object_size <= 512       - 64   ? 64 :
 225                 object_size <= 4096      - 128  ? 128 :
 226                 object_size <= (1 << 14) - 256  ? 256 :
 227                 object_size <= (1 << 15) - 512  ? 512 :
 228                 object_size <= (1 << 16) - 1024 ? 1024 : 2048;
 229 }
 230
 231 void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 232                         slab_flags_t *flags)
 233 {
 234         unsigned int orig_size = *size;
 235         int redzone_adjust;
 236
 237         /* Add alloc meta. */
 238         cache->kasan_info.alloc_meta_offset = *size;
 239         *size += sizeof(struct kasan_alloc_meta);
 240
 241         /* Add free meta. */
 242         if (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
 243             cache->object_size < sizeof(struct kasan_free_meta)) {
 244                 cache->kasan_info.free_meta_offset = *size;
 245                 *size += sizeof(struct kasan_free_meta);
 246         }
 247         redzone_adjust = optimal_redzone(cache->object_size) -
 248                 (*size - cache->object_size);
 249
 250         if (redzone_adjust > 0)
 251                 *size += redzone_adjust;
 252
 253         *size = min_t(unsigned int, KMALLOC_MAX_SIZE,
 254                         max(*size, cache->object_size +
 255                                         optimal_redzone(cache->object_size)));
 256
 257         /*
 258          * If the metadata doesn't fit, don't enable KASAN at all.
 259          */
 260         if (*size <= cache->kasan_info.alloc_meta_offset ||
 261                         *size <= cache->kasan_info.free_meta_offset) {
 262                 cache->kasan_info.alloc_meta_offset = 0;
 263                 cache->kasan_info.free_meta_offset = 0;
 264                 *size = orig_size;
 265                 return;
 266         }
 267
 268         *flags |= SLAB_KASAN;
 269 }
 270
 271 size_t kasan_metadata_size(struct kmem_cache *cache)
 272 {
 273         return (cache->kasan_info.alloc_meta_offset ?
 274                 sizeof(struct kasan_alloc_meta) : 0) +
 275                 (cache->kasan_info.free_meta_offset ?
 276                 sizeof(struct kasan_free_meta) : 0);
 277 }
 278
 279 struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
 280                                         const void *object)
 281 {
 282         BUILD_BUG_ON(sizeof(struct kasan_alloc_meta) > 32);
 283         return (void *)object + cache->kasan_info.alloc_meta_offset;
 284 }
 285
 286 struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
 287                                       const void *object)
 288 {
 289         BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
 290         return (void *)object + cache->kasan_info.free_meta_offset;
 291 }
 292
 293 void kasan_poison_slab(struct page *page)
 294 {
 295         kasan_poison_shadow(page_address(page),
 296                         PAGE_SIZE << compound_order(page),
 297                         KASAN_KMALLOC_REDZONE);
 298 }
 299
 300 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
 301 {
 302         kasan_unpoison_shadow(object, cache->object_size);
 303 }
 304
 305 void kasan_poison_object_data(struct kmem_cache *cache, void *object)
 306 {
 307         kasan_poison_shadow(object,
 308                         round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
 309                         KASAN_KMALLOC_REDZONE);
 310 }
 311
 312 void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
 313 {
 314         struct kasan_alloc_meta *alloc_info;
 315
 316         if (!(cache->flags & SLAB_KASAN))
 317                 return (void *)object;
 318
 319         alloc_info = get_alloc_info(cache, object);
 320         __memset(alloc_info, 0, sizeof(*alloc_info));
 321
 322         return (void *)object;
 323 }
 324
 325 void *kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
 326 {
 327         return kasan_kmalloc(cache, object, cache->object_size, flags);
 328 }
 329
 330 static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 331                               unsigned long ip, bool quarantine)
 332 {
 333         s8 shadow_byte;
 334         unsigned long rounded_up_size;
 335
 336         if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
 337             object)) {
 338                 kasan_report_invalid_free(object, ip);
 339                 return true;
 340         }
 341
 342         /* RCU slabs could be legally used after free within the RCU period */
 343         if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
 344                 return false;
 345
 346         shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
 347         if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) {
 348                 kasan_report_invalid_free(object, ip);
 349                 return true;
 350         }
 351
 352         rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);
 353         kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 354
 355         if (!quarantine || unlikely(!(cache->flags & SLAB_KASAN)))
 356                 return false;
 357
 358         set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
 359         quarantine_put(get_free_info(cache, object), cache);
 360         return true;
 361 }
 362
 363 bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
 364 {
 365         return __kasan_slab_free(cache, object, ip, true);
 366 }
 367
 368 void *kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
 369                    gfp_t flags)
 370 {
 371         unsigned long redzone_start;
 372         unsigned long redzone_end;
 373
 374         if (gfpflags_allow_blocking(flags))
 375                 quarantine_reduce();
 376
 377         if (unlikely(object == NULL))
 378                 return NULL;
 379
 380         redzone_start = round_up((unsigned long)(object + size),
 381                                 KASAN_SHADOW_SCALE_SIZE);
 382         redzone_end = round_up((unsigned long)object + cache->object_size,
 383                                 KASAN_SHADOW_SCALE_SIZE);
 384
 385         kasan_unpoison_shadow(object, size);
 386         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 387                 KASAN_KMALLOC_REDZONE);
 388
 389         if (cache->flags & SLAB_KASAN)
 390                 set_track(&get_alloc_info(cache, object)->alloc_track, flags);
 391
 392         return (void *)object;
 393 }
 394 EXPORT_SYMBOL(kasan_kmalloc);
 395
 396 void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
 397 {
 398         struct page *page;
 399         unsigned long redzone_start;
 400         unsigned long redzone_end;
 401
 402         if (gfpflags_allow_blocking(flags))
 403                 quarantine_reduce();
 404
 405         if (unlikely(ptr == NULL))
 406                 return NULL;
 407
 408         page = virt_to_page(ptr);
 409         redzone_start = round_up((unsigned long)(ptr + size),
 410                                 KASAN_SHADOW_SCALE_SIZE);
 411         redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
 412
 413         kasan_unpoison_shadow(ptr, size);
 414         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 415                 KASAN_PAGE_REDZONE);
 416
 417         return (void *)ptr;
 418 }
 419
 420 void *kasan_krealloc(const void *object, size_t size, gfp_t flags)
 421 {
 422         struct page *page;
 423
 424         if (unlikely(object == ZERO_SIZE_PTR))
 425                 return (void *)object;
 426
 427         page = virt_to_head_page(object);
 428
 429         if (unlikely(!PageSlab(page)))
 430                 return kasan_kmalloc_large(object, size, flags);
 431         else
 432                 return kasan_kmalloc(page->slab_cache, object, size, flags);
 433 }
 434
 435 void kasan_poison_kfree(void *ptr, unsigned long ip)
 436 {
 437         struct page *page;
 438
 439         page = virt_to_head_page(ptr);
 440
 441         if (unlikely(!PageSlab(page))) {
 442                 if (ptr != page_address(page)) {
 443                         kasan_report_invalid_free(ptr, ip);
 444                         return;
 445                 }
 446                 kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 447                                 KASAN_FREE_PAGE);
 448         } else {
 449                 __kasan_slab_free(page->slab_cache, ptr, ip, false);
 450         }
 451 }
 452
 453 void kasan_kfree_large(void *ptr, unsigned long ip)
 454 {
 455         if (ptr != page_address(virt_to_head_page(ptr)))
 456                 kasan_report_invalid_free(ptr, ip);
 457         /* The object will be poisoned by page_alloc. */
 458 }
 459
 460 int kasan_module_alloc(void *addr, size_t size)
 461 {
 462         void *ret;
 463         size_t scaled_size;
 464         size_t shadow_size;
 465         unsigned long shadow_start;
 466
 467         shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
 468         scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
 469         shadow_size = round_up(scaled_size, PAGE_SIZE);
 470
 471         if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
 472                 return -EINVAL;
 473
 474         ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 475                         shadow_start + shadow_size,
 476                         GFP_KERNEL | __GFP_ZERO,
 477                         PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 478                         __builtin_return_address(0));
 479
 480         if (ret) {
 481                 find_vm_area(addr)->flags |= VM_KASAN;
 482                 kmemleak_ignore(ret);
 483                 return 0;
 484         }
 485
 486         return -ENOMEM;
 487 }
 488
 489 void kasan_free_shadow(const struct vm_struct *vm)
 490 {
 491         if (vm->flags & VM_KASAN)
 492                 vfree(kasan_mem_to_shadow(vm->addr));
 493 }
 494
 495 #ifdef CONFIG_MEMORY_HOTPLUG
 496 static bool shadow_mapped(unsigned long addr)
 497 {
 498         pgd_t *pgd = pgd_offset_k(addr);
 499         p4d_t *p4d;
 500         pud_t *pud;
 501         pmd_t *pmd;
 502         pte_t *pte;
 503
 504         if (pgd_none(*pgd))
 505                 return false;
 506         p4d = p4d_offset(pgd, addr);
 507         if (p4d_none(*p4d))
 508                 return false;
 509         pud = pud_offset(p4d, addr);
 510         if (pud_none(*pud))
 511                 return false;
 512
 513         /*
 514          * We can't use pud_large() or pud_huge(), the first one is
 515          * arch-specific, the last one depends on HUGETLB_PAGE.  So let's abuse
 516          * pud_bad(), if pud is bad then it's bad because it's huge.
 517          */
 518         if (pud_bad(*pud))
 519                 return true;
 520         pmd = pmd_offset(pud, addr);
 521         if (pmd_none(*pmd))
 522                 return false;
 523
 524         if (pmd_bad(*pmd))
 525                 return true;
 526         pte = pte_offset_kernel(pmd, addr);
 527         return !pte_none(*pte);
 528 }
 529
 530 static int __meminit kasan_mem_notifier(struct notifier_block *nb,
 531                         unsigned long action, void *data)
 532 {
 533         struct memory_notify *mem_data = data;
 534         unsigned long nr_shadow_pages, start_kaddr, shadow_start;
 535         unsigned long shadow_end, shadow_size;
 536
 537         nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
 538         start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
 539         shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
 540         shadow_size = nr_shadow_pages << PAGE_SHIFT;
 541         shadow_end = shadow_start + shadow_size;
 542
 543         if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
 544                 WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
 545                 return NOTIFY_BAD;
 546
 547         switch (action) {
 548         case MEM_GOING_ONLINE: {
 549                 void *ret;
 550
 551                 /*
 552                  * If shadow is mapped already than it must have been mapped
 553                  * during the boot. This could happen if we onlining previously
 554                  * offlined memory.
 555                  */
 556                 if (shadow_mapped(shadow_start))
 557                         return NOTIFY_OK;
 558
 559                 ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
 560                                         shadow_end, GFP_KERNEL,
 561                                         PAGE_KERNEL, VM_NO_GUARD,
 562                                         pfn_to_nid(mem_data->start_pfn),
 563                                         __builtin_return_address(0));
 564                 if (!ret)
 565                         return NOTIFY_BAD;
 566
 567                 kmemleak_ignore(ret);
 568                 return NOTIFY_OK;
 569         }
 570         case MEM_CANCEL_ONLINE:
 571         case MEM_OFFLINE: {
 572                 struct vm_struct *vm;
 573
 574                 /*
 575                  * shadow_start was either mapped during boot by kasan_init()
 576                  * or during memory online by __vmalloc_node_range().
 577                  * In the latter case we can use vfree() to free shadow.
 578                  * Non-NULL result of the find_vm_area() will tell us if
 579                  * that was the second case.
 580                  *
 581                  * Currently it's not possible to free shadow mapped
 582                  * during boot by kasan_init(). It's because the code
 583                  * to do that hasn't been written yet. So we'll just
 584                  * leak the memory.
 585                  */
 586                 vm = find_vm_area((void *)shadow_start);
 587                 if (vm)
 588                         vfree((void *)shadow_start);
 589         }
 590         }
 591
 592         return NOTIFY_OK;
 593 }
 594
 595 static int __init kasan_memhotplug_init(void)
 596 {
 597         hotplug_memory_notifier(kasan_mem_notifier, 0);
 598
 599         return 0;
 600 }
 601
 602 core_initcall(kasan_memhotplug_init);
 603 #endif