mm/kmsan/shadow.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * KMSAN shadow implementation.
   4  *
   5  * Copyright (C) 2017-2022 Google LLC
   6  * Author: Alexander Potapenko <glider@google.com>
   7  *
   8  */
   9
  10 #include <asm/kmsan.h>
  11 #include <asm/tlbflush.h>
  12 #include <linux/cacheflush.h>
  13 #include <linux/memblock.h>
  14 #include <linux/mm_types.h>
  15 #include <linux/slab.h>
  16 #include <linux/smp.h>
  17 #include <linux/stddef.h>
  18
  19 #include "../internal.h"
  20 #include "kmsan.h"
  21
  22 #define shadow_page_for(page) ((page)->kmsan_shadow)
  23
  24 #define origin_page_for(page) ((page)->kmsan_origin)
  25
  26 static void *shadow_ptr_for(struct page *page)
  27 {
  28         return page_address(shadow_page_for(page));
  29 }
  30
  31 static void *origin_ptr_for(struct page *page)
  32 {
  33         return page_address(origin_page_for(page));
  34 }
  35
  36 static bool page_has_metadata(struct page *page)
  37 {
  38         return shadow_page_for(page) && origin_page_for(page);
  39 }
  40
  41 static void set_no_shadow_origin_page(struct page *page)
  42 {
  43         shadow_page_for(page) = NULL;
  44         origin_page_for(page) = NULL;
  45 }
  46
  47 /*
  48  * Dummy load and store pages to be used when the real metadata is unavailable.
  49  * There are separate pages for loads and stores, so that every load returns a
  50  * zero, and every store doesn't affect other loads.
  51  */
  52 static char dummy_load_page[PAGE_SIZE] __aligned(PAGE_SIZE);
  53 static char dummy_store_page[PAGE_SIZE] __aligned(PAGE_SIZE);
  54
  55 static unsigned long vmalloc_meta(void *addr, bool is_origin)
  56 {
  57         unsigned long addr64 = (unsigned long)addr, off;
  58
  59         KMSAN_WARN_ON(is_origin && !IS_ALIGNED(addr64, KMSAN_ORIGIN_SIZE));
  60         if (kmsan_internal_is_vmalloc_addr(addr)) {
  61                 off = addr64 - VMALLOC_START;
  62                 return off + (is_origin ? KMSAN_VMALLOC_ORIGIN_START :
  63                                           KMSAN_VMALLOC_SHADOW_START);
  64         }
  65         if (kmsan_internal_is_module_addr(addr)) {
  66                 off = addr64 - MODULES_VADDR;
  67                 return off + (is_origin ? KMSAN_MODULES_ORIGIN_START :
  68                                           KMSAN_MODULES_SHADOW_START);
  69         }
  70         return 0;
  71 }
  72
  73 static struct page *virt_to_page_or_null(void *vaddr)
  74 {
  75         if (kmsan_virt_addr_valid(vaddr))
  76                 return virt_to_page(vaddr);
  77         else
  78                 return NULL;
  79 }
  80
  81 struct shadow_origin_ptr kmsan_get_shadow_origin_ptr(void *address, u64 size,
  82                                                      bool store)
  83 {
  84         struct shadow_origin_ptr ret;
  85         void *shadow;
  86
  87         /*
  88          * Even if we redirect this memory access to the dummy page, it will
  89          * go out of bounds.
  90          */
  91         KMSAN_WARN_ON(size > PAGE_SIZE);
  92
  93         if (!kmsan_enabled)
  94                 goto return_dummy;
  95
  96         KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(address, size));
  97         shadow = kmsan_get_metadata(address, KMSAN_META_SHADOW);
  98         if (!shadow)
  99                 goto return_dummy;
 100
 101         ret.shadow = shadow;
 102         ret.origin = kmsan_get_metadata(address, KMSAN_META_ORIGIN);
 103         return ret;
 104
 105 return_dummy:
 106         if (store) {
 107                 /* Ignore this store. */
 108                 ret.shadow = dummy_store_page;
 109                 ret.origin = dummy_store_page;
 110         } else {
 111                 /* This load will return zero. */
 112                 ret.shadow = dummy_load_page;
 113                 ret.origin = dummy_load_page;
 114         }
 115         return ret;
 116 }
 117
 118 /*
 119  * Obtain the shadow or origin pointer for the given address, or NULL if there's
 120  * none. The caller must check the return value for being non-NULL if needed.
 121  * The return value of this function should not depend on whether we're in the
 122  * runtime or not.
 123  */
 124 void *kmsan_get_metadata(void *address, bool is_origin)
 125 {
 126         u64 addr = (u64)address, pad, off;
 127         struct page *page;
 128         void *ret;
 129
 130         if (is_origin && !IS_ALIGNED(addr, KMSAN_ORIGIN_SIZE)) {
 131                 pad = addr % KMSAN_ORIGIN_SIZE;
 132                 addr -= pad;
 133         }
 134         address = (void *)addr;
 135         if (kmsan_internal_is_vmalloc_addr(address) ||
 136             kmsan_internal_is_module_addr(address))
 137                 return (void *)vmalloc_meta(address, is_origin);
 138
 139         ret = arch_kmsan_get_meta_or_null(address, is_origin);
 140         if (ret)
 141                 return ret;
 142
 143         page = virt_to_page_or_null(address);
 144         if (!page)
 145                 return NULL;
 146         if (!page_has_metadata(page))
 147                 return NULL;
 148         off = offset_in_page(addr);
 149
 150         return (is_origin ? origin_ptr_for(page) : shadow_ptr_for(page)) + off;
 151 }
 152
 153 void kmsan_copy_page_meta(struct page *dst, struct page *src)
 154 {
 155         if (!kmsan_enabled || kmsan_in_runtime())
 156                 return;
 157         if (!dst || !page_has_metadata(dst))
 158                 return;
 159         if (!src || !page_has_metadata(src)) {
 160                 kmsan_internal_unpoison_memory(page_address(dst), PAGE_SIZE,
 161                                                /*checked*/ false);
 162                 return;
 163         }
 164
 165         kmsan_enter_runtime();
 166         __memcpy(shadow_ptr_for(dst), shadow_ptr_for(src), PAGE_SIZE);
 167         __memcpy(origin_ptr_for(dst), origin_ptr_for(src), PAGE_SIZE);
 168         kmsan_leave_runtime();
 169 }
 170 EXPORT_SYMBOL(kmsan_copy_page_meta);
 171
 172 void kmsan_alloc_page(struct page *page, unsigned int order, gfp_t flags)
 173 {
 174         bool initialized = (flags & __GFP_ZERO) || !kmsan_enabled;
 175         struct page *shadow, *origin;
 176         depot_stack_handle_t handle;
 177         int pages = 1 << order;
 178
 179         if (!page)
 180                 return;
 181
 182         shadow = shadow_page_for(page);
 183         origin = origin_page_for(page);
 184
 185         if (initialized) {
 186                 __memset(page_address(shadow), 0, PAGE_SIZE * pages);
 187                 __memset(page_address(origin), 0, PAGE_SIZE * pages);
 188                 return;
 189         }
 190
 191         /* Zero pages allocated by the runtime should also be initialized. */
 192         if (kmsan_in_runtime())
 193                 return;
 194
 195         __memset(page_address(shadow), -1, PAGE_SIZE * pages);
 196         kmsan_enter_runtime();
 197         handle = kmsan_save_stack_with_flags(flags, /*extra_bits*/ 0);
 198         kmsan_leave_runtime();
 199         /*
 200          * Addresses are page-aligned, pages are contiguous, so it's ok
 201          * to just fill the origin pages with @handle.
 202          */
 203         for (int i = 0; i < PAGE_SIZE * pages / sizeof(handle); i++)
 204                 ((depot_stack_handle_t *)page_address(origin))[i] = handle;
 205 }
 206
 207 void kmsan_free_page(struct page *page, unsigned int order)
 208 {
 209         if (!kmsan_enabled || kmsan_in_runtime())
 210                 return;
 211         kmsan_enter_runtime();
 212         kmsan_internal_poison_memory(page_address(page),
 213                                      page_size(page),
 214                                      GFP_KERNEL,
 215                                      KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
 216         kmsan_leave_runtime();
 217 }
 218
 219 int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,
 220                                    pgprot_t prot, struct page **pages,
 221                                    unsigned int page_shift)
 222 {
 223         unsigned long shadow_start, origin_start, shadow_end, origin_end;
 224         struct page **s_pages, **o_pages;
 225         int nr, mapped, err = 0;
 226
 227         if (!kmsan_enabled)
 228                 return 0;
 229
 230         shadow_start = vmalloc_meta((void *)start, KMSAN_META_SHADOW);
 231         shadow_end = vmalloc_meta((void *)end, KMSAN_META_SHADOW);
 232         if (!shadow_start)
 233                 return 0;
 234
 235         nr = (end - start) / PAGE_SIZE;
 236         s_pages = kcalloc(nr, sizeof(*s_pages), GFP_KERNEL);
 237         o_pages = kcalloc(nr, sizeof(*o_pages), GFP_KERNEL);
 238         if (!s_pages || !o_pages) {
 239                 err = -ENOMEM;
 240                 goto ret;
 241         }
 242         for (int i = 0; i < nr; i++) {
 243                 s_pages[i] = shadow_page_for(pages[i]);
 244                 o_pages[i] = origin_page_for(pages[i]);
 245         }
 246         prot = __pgprot(pgprot_val(prot) | _PAGE_NX);
 247         prot = PAGE_KERNEL;
 248
 249         origin_start = vmalloc_meta((void *)start, KMSAN_META_ORIGIN);
 250         origin_end = vmalloc_meta((void *)end, KMSAN_META_ORIGIN);
 251         kmsan_enter_runtime();
 252         mapped = __vmap_pages_range_noflush(shadow_start, shadow_end, prot,
 253                                             s_pages, page_shift);
 254         if (mapped) {
 255                 err = mapped;
 256                 goto ret;
 257         }
 258         mapped = __vmap_pages_range_noflush(origin_start, origin_end, prot,
 259                                             o_pages, page_shift);
 260         if (mapped) {
 261                 err = mapped;
 262                 goto ret;
 263         }
 264         kmsan_leave_runtime();
 265         flush_tlb_kernel_range(shadow_start, shadow_end);
 266         flush_tlb_kernel_range(origin_start, origin_end);
 267         flush_cache_vmap(shadow_start, shadow_end);
 268         flush_cache_vmap(origin_start, origin_end);
 269
 270 ret:
 271         kfree(s_pages);
 272         kfree(o_pages);
 273         return err;
 274 }
 275
 276 /* Allocate metadata for pages allocated at boot time. */
 277 void __init kmsan_init_alloc_meta_for_range(void *start, void *end)
 278 {
 279         struct page *shadow_p, *origin_p;
 280         void *shadow, *origin;
 281         struct page *page;
 282         u64 size;
 283
 284         start = (void *)PAGE_ALIGN_DOWN((u64)start);
 285         size = PAGE_ALIGN((u64)end - (u64)start);
 286         shadow = memblock_alloc(size, PAGE_SIZE);
 287         origin = memblock_alloc(size, PAGE_SIZE);
 288         for (u64 addr = 0; addr < size; addr += PAGE_SIZE) {
 289                 page = virt_to_page_or_null((char *)start + addr);
 290                 shadow_p = virt_to_page_or_null((char *)shadow + addr);
 291                 set_no_shadow_origin_page(shadow_p);
 292                 shadow_page_for(page) = shadow_p;
 293                 origin_p = virt_to_page_or_null((char *)origin + addr);
 294                 set_no_shadow_origin_page(origin_p);
 295                 origin_page_for(page) = origin_p;
 296         }
 297 }
 298
 299 void kmsan_setup_meta(struct page *page, struct page *shadow,
 300                       struct page *origin, int order)
 301 {
 302         for (int i = 0; i < (1 << order); i++) {
 303                 set_no_shadow_origin_page(&shadow[i]);
 304                 set_no_shadow_origin_page(&origin[i]);
 305                 shadow_page_for(&page[i]) = &shadow[i];
 306                 origin_page_for(&page[i]) = &origin[i];
 307         }
 308 }