1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * KMSAN runtime library. 4 * 5 * Copyright (C) 2017-2022 Google LLC 6 * Author: Alexander Potapenko <glider@google.com> 7 * 8 */ 9 10 #include <asm/page.h> 11 #include <linux/compiler.h> 12 #include <linux/export.h> 13 #include <linux/highmem.h> 14 #include <linux/interrupt.h> 15 #include <linux/kernel.h> 16 #include <linux/kmsan_types.h> 17 #include <linux/memory.h> 18 #include <linux/mm.h> 19 #include <linux/mm_types.h> 20 #include <linux/mmzone.h> 21 #include <linux/percpu-defs.h> 22 #include <linux/preempt.h> 23 #include <linux/slab.h> 24 #include <linux/stackdepot.h> 25 #include <linux/stacktrace.h> 26 #include <linux/types.h> 27 #include <linux/vmalloc.h> 28 29 #include "../slab.h" 30 #include "kmsan.h" 31 32 bool kmsan_enabled __read_mostly; 33 34 /* 35 * Per-CPU KMSAN context to be used in interrupts, where current->kmsan is 36 * unavaliable. 37 */ 38 DEFINE_PER_CPU(struct kmsan_ctx, kmsan_percpu_ctx); 39 40 void kmsan_internal_task_create(struct task_struct *task) 41 { 42 struct kmsan_ctx *ctx = &task->kmsan_ctx; 43 struct thread_info *info = current_thread_info(); 44 45 __memset(ctx, 0, sizeof(*ctx)); 46 ctx->allow_reporting = true; 47 kmsan_internal_unpoison_memory(info, sizeof(*info), false); 48 } 49 50 void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags, 51 unsigned int poison_flags) 52 { 53 u32 extra_bits = 54 kmsan_extra_bits(/*depth*/ 0, poison_flags & KMSAN_POISON_FREE); 55 bool checked = poison_flags & KMSAN_POISON_CHECK; 56 depot_stack_handle_t handle; 57 58 handle = kmsan_save_stack_with_flags(flags, extra_bits); 59 kmsan_internal_set_shadow_origin(address, size, -1, handle, checked); 60 } 61 62 void kmsan_internal_unpoison_memory(void *address, size_t size, bool checked) 63 { 64 kmsan_internal_set_shadow_origin(address, size, 0, 0, checked); 65 } 66 67 depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags, 68 unsigned int extra) 69 { 70 unsigned long entries[KMSAN_STACK_DEPTH]; 71 unsigned int nr_entries; 72 depot_stack_handle_t handle; 73 74 nr_entries = stack_trace_save(entries, KMSAN_STACK_DEPTH, 0); 75 76 /* Don't sleep. */ 77 flags &= ~(__GFP_DIRECT_RECLAIM | __GFP_KSWAPD_RECLAIM); 78 79 handle = stack_depot_save(entries, nr_entries, flags); 80 return stack_depot_set_extra_bits(handle, extra); 81 } 82 83 /* Copy the metadata following the memmove() behavior. */ 84 void kmsan_internal_memmove_metadata(void *dst, void *src, size_t n) 85 { 86 depot_stack_handle_t prev_old_origin = 0, prev_new_origin = 0; 87 int i, iter, step, src_off, dst_off, oiter_src, oiter_dst; 88 depot_stack_handle_t old_origin = 0, new_origin = 0; 89 depot_stack_handle_t *origin_src, *origin_dst; 90 u8 *shadow_src, *shadow_dst; 91 u32 *align_shadow_dst; 92 bool backwards; 93 94 shadow_dst = kmsan_get_metadata(dst, KMSAN_META_SHADOW); 95 if (!shadow_dst) 96 return; 97 KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(dst, n)); 98 align_shadow_dst = 99 (u32 *)ALIGN_DOWN((u64)shadow_dst, KMSAN_ORIGIN_SIZE); 100 101 shadow_src = kmsan_get_metadata(src, KMSAN_META_SHADOW); 102 if (!shadow_src) { 103 /* @src is untracked: mark @dst as initialized. */ 104 kmsan_internal_unpoison_memory(dst, n, /*checked*/ false); 105 return; 106 } 107 KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(src, n)); 108 109 origin_dst = kmsan_get_metadata(dst, KMSAN_META_ORIGIN); 110 origin_src = kmsan_get_metadata(src, KMSAN_META_ORIGIN); 111 KMSAN_WARN_ON(!origin_dst || !origin_src); 112 113 backwards = dst > src; 114 step = backwards ? -1 : 1; 115 iter = backwards ? n - 1 : 0; 116 src_off = (u64)src % KMSAN_ORIGIN_SIZE; 117 dst_off = (u64)dst % KMSAN_ORIGIN_SIZE; 118 119 /* Copy shadow bytes one by one, updating the origins if necessary. */ 120 for (i = 0; i < n; i++, iter += step) { 121 oiter_src = (iter + src_off) / KMSAN_ORIGIN_SIZE; 122 oiter_dst = (iter + dst_off) / KMSAN_ORIGIN_SIZE; 123 if (!shadow_src[iter]) { 124 shadow_dst[iter] = 0; 125 if (!align_shadow_dst[oiter_dst]) 126 origin_dst[oiter_dst] = 0; 127 continue; 128 } 129 shadow_dst[iter] = shadow_src[iter]; 130 old_origin = origin_src[oiter_src]; 131 if (old_origin == prev_old_origin) 132 new_origin = prev_new_origin; 133 else { 134 /* 135 * kmsan_internal_chain_origin() may return 136 * NULL, but we don't want to lose the previous 137 * origin value. 138 */ 139 new_origin = kmsan_internal_chain_origin(old_origin); 140 if (!new_origin) 141 new_origin = old_origin; 142 } 143 origin_dst[oiter_dst] = new_origin; 144 prev_new_origin = new_origin; 145 prev_old_origin = old_origin; 146 } 147 } 148 149 depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id) 150 { 151 unsigned long entries[3]; 152 u32 extra_bits; 153 int depth; 154 bool uaf; 155 depot_stack_handle_t handle; 156 157 if (!id) 158 return id; 159 /* 160 * Make sure we have enough spare bits in @id to hold the UAF bit and 161 * the chain depth. 162 */ 163 BUILD_BUG_ON( 164 (1 << STACK_DEPOT_EXTRA_BITS) <= (KMSAN_MAX_ORIGIN_DEPTH << 1)); 165 166 extra_bits = stack_depot_get_extra_bits(id); 167 depth = kmsan_depth_from_eb(extra_bits); 168 uaf = kmsan_uaf_from_eb(extra_bits); 169 170 /* 171 * Stop chaining origins once the depth reached KMSAN_MAX_ORIGIN_DEPTH. 172 * This mostly happens in the case structures with uninitialized padding 173 * are copied around many times. Origin chains for such structures are 174 * usually periodic, and it does not make sense to fully store them. 175 */ 176 if (depth == KMSAN_MAX_ORIGIN_DEPTH) 177 return id; 178 179 depth++; 180 extra_bits = kmsan_extra_bits(depth, uaf); 181 182 entries[0] = KMSAN_CHAIN_MAGIC_ORIGIN; 183 entries[1] = kmsan_save_stack_with_flags(__GFP_HIGH, 0); 184 entries[2] = id; 185 /* 186 * @entries is a local var in non-instrumented code, so KMSAN does not 187 * know it is initialized. Explicitly unpoison it to avoid false 188 * positives when stack_depot_save() passes it to instrumented code. 189 */ 190 kmsan_internal_unpoison_memory(entries, sizeof(entries), false); 191 handle = stack_depot_save(entries, ARRAY_SIZE(entries), __GFP_HIGH); 192 return stack_depot_set_extra_bits(handle, extra_bits); 193 } 194 195 void kmsan_internal_set_shadow_origin(void *addr, size_t size, int b, 196 u32 origin, bool checked) 197 { 198 u64 address = (u64)addr; 199 void *shadow_start; 200 u32 *origin_start; 201 size_t pad = 0; 202 203 KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size)); 204 shadow_start = kmsan_get_metadata(addr, KMSAN_META_SHADOW); 205 if (!shadow_start) { 206 /* 207 * kmsan_metadata_is_contiguous() is true, so either all shadow 208 * and origin pages are NULL, or all are non-NULL. 209 */ 210 if (checked) { 211 pr_err("%s: not memsetting %ld bytes starting at %px, because the shadow is NULL\n", 212 __func__, size, addr); 213 KMSAN_WARN_ON(true); 214 } 215 return; 216 } 217 __memset(shadow_start, b, size); 218 219 if (!IS_ALIGNED(address, KMSAN_ORIGIN_SIZE)) { 220 pad = address % KMSAN_ORIGIN_SIZE; 221 address -= pad; 222 size += pad; 223 } 224 size = ALIGN(size, KMSAN_ORIGIN_SIZE); 225 origin_start = 226 (u32 *)kmsan_get_metadata((void *)address, KMSAN_META_ORIGIN); 227 228 for (int i = 0; i < size / KMSAN_ORIGIN_SIZE; i++) 229 origin_start[i] = origin; 230 } 231 232 struct page *kmsan_vmalloc_to_page_or_null(void *vaddr) 233 { 234 struct page *page; 235 236 if (!kmsan_internal_is_vmalloc_addr(vaddr) && 237 !kmsan_internal_is_module_addr(vaddr)) 238 return NULL; 239 page = vmalloc_to_page(vaddr); 240 if (pfn_valid(page_to_pfn(page))) 241 return page; 242 else 243 return NULL; 244 } 245 246 void kmsan_internal_check_memory(void *addr, size_t size, const void *user_addr, 247 int reason) 248 { 249 depot_stack_handle_t cur_origin = 0, new_origin = 0; 250 unsigned long addr64 = (unsigned long)addr; 251 depot_stack_handle_t *origin = NULL; 252 unsigned char *shadow = NULL; 253 int cur_off_start = -1; 254 int chunk_size; 255 size_t pos = 0; 256 257 if (!size) 258 return; 259 KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size)); 260 while (pos < size) { 261 chunk_size = min(size - pos, 262 PAGE_SIZE - ((addr64 + pos) % PAGE_SIZE)); 263 shadow = kmsan_get_metadata((void *)(addr64 + pos), 264 KMSAN_META_SHADOW); 265 if (!shadow) { 266 /* 267 * This page is untracked. If there were uninitialized 268 * bytes before, report them. 269 */ 270 if (cur_origin) { 271 kmsan_enter_runtime(); 272 kmsan_report(cur_origin, addr, size, 273 cur_off_start, pos - 1, user_addr, 274 reason); 275 kmsan_leave_runtime(); 276 } 277 cur_origin = 0; 278 cur_off_start = -1; 279 pos += chunk_size; 280 continue; 281 } 282 for (int i = 0; i < chunk_size; i++) { 283 if (!shadow[i]) { 284 /* 285 * This byte is unpoisoned. If there were 286 * poisoned bytes before, report them. 287 */ 288 if (cur_origin) { 289 kmsan_enter_runtime(); 290 kmsan_report(cur_origin, addr, size, 291 cur_off_start, pos + i - 1, 292 user_addr, reason); 293 kmsan_leave_runtime(); 294 } 295 cur_origin = 0; 296 cur_off_start = -1; 297 continue; 298 } 299 origin = kmsan_get_metadata((void *)(addr64 + pos + i), 300 KMSAN_META_ORIGIN); 301 KMSAN_WARN_ON(!origin); 302 new_origin = *origin; 303 /* 304 * Encountered new origin - report the previous 305 * uninitialized range. 306 */ 307 if (cur_origin != new_origin) { 308 if (cur_origin) { 309 kmsan_enter_runtime(); 310 kmsan_report(cur_origin, addr, size, 311 cur_off_start, pos + i - 1, 312 user_addr, reason); 313 kmsan_leave_runtime(); 314 } 315 cur_origin = new_origin; 316 cur_off_start = pos + i; 317 } 318 } 319 pos += chunk_size; 320 } 321 KMSAN_WARN_ON(pos != size); 322 if (cur_origin) { 323 kmsan_enter_runtime(); 324 kmsan_report(cur_origin, addr, size, cur_off_start, pos - 1, 325 user_addr, reason); 326 kmsan_leave_runtime(); 327 } 328 } 329 330 bool kmsan_metadata_is_contiguous(void *addr, size_t size) 331 { 332 char *cur_shadow = NULL, *next_shadow = NULL, *cur_origin = NULL, 333 *next_origin = NULL; 334 u64 cur_addr = (u64)addr, next_addr = cur_addr + PAGE_SIZE; 335 depot_stack_handle_t *origin_p; 336 bool all_untracked = false; 337 338 if (!size) 339 return true; 340 341 /* The whole range belongs to the same page. */ 342 if (ALIGN_DOWN(cur_addr + size - 1, PAGE_SIZE) == 343 ALIGN_DOWN(cur_addr, PAGE_SIZE)) 344 return true; 345 346 cur_shadow = kmsan_get_metadata((void *)cur_addr, /*is_origin*/ false); 347 if (!cur_shadow) 348 all_untracked = true; 349 cur_origin = kmsan_get_metadata((void *)cur_addr, /*is_origin*/ true); 350 if (all_untracked && cur_origin) 351 goto report; 352 353 for (; next_addr < (u64)addr + size; 354 cur_addr = next_addr, cur_shadow = next_shadow, 355 cur_origin = next_origin, next_addr += PAGE_SIZE) { 356 next_shadow = kmsan_get_metadata((void *)next_addr, false); 357 next_origin = kmsan_get_metadata((void *)next_addr, true); 358 if (all_untracked) { 359 if (next_shadow || next_origin) 360 goto report; 361 if (!next_shadow && !next_origin) 362 continue; 363 } 364 if (((u64)cur_shadow == ((u64)next_shadow - PAGE_SIZE)) && 365 ((u64)cur_origin == ((u64)next_origin - PAGE_SIZE))) 366 continue; 367 goto report; 368 } 369 return true; 370 371 report: 372 pr_err("%s: attempting to access two shadow page ranges.\n", __func__); 373 pr_err("Access of size %ld at %px.\n", size, addr); 374 pr_err("Addresses belonging to different ranges: %px and %px\n", 375 (void *)cur_addr, (void *)next_addr); 376 pr_err("page[0].shadow: %px, page[1].shadow: %px\n", cur_shadow, 377 next_shadow); 378 pr_err("page[0].origin: %px, page[1].origin: %px\n", cur_origin, 379 next_origin); 380 origin_p = kmsan_get_metadata(addr, KMSAN_META_ORIGIN); 381 if (origin_p) { 382 pr_err("Origin: %08x\n", *origin_p); 383 kmsan_print_origin(*origin_p); 384 } else { 385 pr_err("Origin: unavailable\n"); 386 } 387 return false; 388 } 389