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 kmsan_internal_unpoison_memory(info, sizeof(*info), false); 47 } 48 49 void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags, 50 unsigned int poison_flags) 51 { 52 u32 extra_bits = 53 kmsan_extra_bits(/*depth*/ 0, poison_flags & KMSAN_POISON_FREE); 54 bool checked = poison_flags & KMSAN_POISON_CHECK; 55 depot_stack_handle_t handle; 56 57 handle = kmsan_save_stack_with_flags(flags, extra_bits); 58 kmsan_internal_set_shadow_origin(address, size, -1, handle, checked); 59 } 60 61 void kmsan_internal_unpoison_memory(void *address, size_t size, bool checked) 62 { 63 kmsan_internal_set_shadow_origin(address, size, 0, 0, checked); 64 } 65 66 depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags, 67 unsigned int extra) 68 { 69 unsigned long entries[KMSAN_STACK_DEPTH]; 70 unsigned int nr_entries; 71 depot_stack_handle_t handle; 72 73 nr_entries = stack_trace_save(entries, KMSAN_STACK_DEPTH, 0); 74 75 /* Don't sleep. */ 76 flags &= ~(__GFP_DIRECT_RECLAIM | __GFP_KSWAPD_RECLAIM); 77 78 handle = stack_depot_save(entries, nr_entries, flags); 79 return stack_depot_set_extra_bits(handle, extra); 80 } 81 82 /* Copy the metadata following the memmove() behavior. */ 83 void kmsan_internal_memmove_metadata(void *dst, void *src, size_t n) 84 { 85 depot_stack_handle_t prev_old_origin = 0, prev_new_origin = 0; 86 int i, iter, step, src_off, dst_off, oiter_src, oiter_dst; 87 depot_stack_handle_t old_origin = 0, new_origin = 0; 88 depot_stack_handle_t *origin_src, *origin_dst; 89 u8 *shadow_src, *shadow_dst; 90 u32 *align_shadow_dst; 91 bool backwards; 92 93 shadow_dst = kmsan_get_metadata(dst, KMSAN_META_SHADOW); 94 if (!shadow_dst) 95 return; 96 KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(dst, n)); 97 align_shadow_dst = 98 (u32 *)ALIGN_DOWN((u64)shadow_dst, KMSAN_ORIGIN_SIZE); 99 100 shadow_src = kmsan_get_metadata(src, KMSAN_META_SHADOW); 101 if (!shadow_src) { 102 /* @src is untracked: mark @dst as initialized. */ 103 kmsan_internal_unpoison_memory(dst, n, /*checked*/ false); 104 return; 105 } 106 KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(src, n)); 107 108 origin_dst = kmsan_get_metadata(dst, KMSAN_META_ORIGIN); 109 origin_src = kmsan_get_metadata(src, KMSAN_META_ORIGIN); 110 KMSAN_WARN_ON(!origin_dst || !origin_src); 111 112 backwards = dst > src; 113 step = backwards ? -1 : 1; 114 iter = backwards ? n - 1 : 0; 115 src_off = (u64)src % KMSAN_ORIGIN_SIZE; 116 dst_off = (u64)dst % KMSAN_ORIGIN_SIZE; 117 118 /* Copy shadow bytes one by one, updating the origins if necessary. */ 119 for (i = 0; i < n; i++, iter += step) { 120 oiter_src = (iter + src_off) / KMSAN_ORIGIN_SIZE; 121 oiter_dst = (iter + dst_off) / KMSAN_ORIGIN_SIZE; 122 if (!shadow_src[iter]) { 123 shadow_dst[iter] = 0; 124 if (!align_shadow_dst[oiter_dst]) 125 origin_dst[oiter_dst] = 0; 126 continue; 127 } 128 shadow_dst[iter] = shadow_src[iter]; 129 old_origin = origin_src[oiter_src]; 130 if (old_origin == prev_old_origin) 131 new_origin = prev_new_origin; 132 else { 133 /* 134 * kmsan_internal_chain_origin() may return 135 * NULL, but we don't want to lose the previous 136 * origin value. 137 */ 138 new_origin = kmsan_internal_chain_origin(old_origin); 139 if (!new_origin) 140 new_origin = old_origin; 141 } 142 origin_dst[oiter_dst] = new_origin; 143 prev_new_origin = new_origin; 144 prev_old_origin = old_origin; 145 } 146 } 147 148 depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id) 149 { 150 unsigned long entries[3]; 151 u32 extra_bits; 152 int depth; 153 bool uaf; 154 depot_stack_handle_t handle; 155 156 if (!id) 157 return id; 158 /* 159 * Make sure we have enough spare bits in @id to hold the UAF bit and 160 * the chain depth. 161 */ 162 BUILD_BUG_ON( 163 (1 << STACK_DEPOT_EXTRA_BITS) <= (KMSAN_MAX_ORIGIN_DEPTH << 1)); 164 165 extra_bits = stack_depot_get_extra_bits(id); 166 depth = kmsan_depth_from_eb(extra_bits); 167 uaf = kmsan_uaf_from_eb(extra_bits); 168 169 /* 170 * Stop chaining origins once the depth reached KMSAN_MAX_ORIGIN_DEPTH. 171 * This mostly happens in the case structures with uninitialized padding 172 * are copied around many times. Origin chains for such structures are 173 * usually periodic, and it does not make sense to fully store them. 174 */ 175 if (depth == KMSAN_MAX_ORIGIN_DEPTH) 176 return id; 177 178 depth++; 179 extra_bits = kmsan_extra_bits(depth, uaf); 180 181 entries[0] = KMSAN_CHAIN_MAGIC_ORIGIN; 182 entries[1] = kmsan_save_stack_with_flags(__GFP_HIGH, 0); 183 entries[2] = id; 184 /* 185 * @entries is a local var in non-instrumented code, so KMSAN does not 186 * know it is initialized. Explicitly unpoison it to avoid false 187 * positives when stack_depot_save() passes it to instrumented code. 188 */ 189 kmsan_internal_unpoison_memory(entries, sizeof(entries), false); 190 handle = stack_depot_save(entries, ARRAY_SIZE(entries), __GFP_HIGH); 191 return stack_depot_set_extra_bits(handle, extra_bits); 192 } 193 194 void kmsan_internal_set_shadow_origin(void *addr, size_t size, int b, 195 u32 origin, bool checked) 196 { 197 u64 address = (u64)addr; 198 u32 *shadow_start, *origin_start; 199 size_t pad = 0; 200 201 KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size)); 202 shadow_start = kmsan_get_metadata(addr, KMSAN_META_SHADOW); 203 if (!shadow_start) { 204 /* 205 * kmsan_metadata_is_contiguous() is true, so either all shadow 206 * and origin pages are NULL, or all are non-NULL. 207 */ 208 if (checked) { 209 pr_err("%s: not memsetting %ld bytes starting at %px, because the shadow is NULL\n", 210 __func__, size, addr); 211 KMSAN_WARN_ON(true); 212 } 213 return; 214 } 215 __memset(shadow_start, b, size); 216 217 if (!IS_ALIGNED(address, KMSAN_ORIGIN_SIZE)) { 218 pad = address % KMSAN_ORIGIN_SIZE; 219 address -= pad; 220 size += pad; 221 } 222 size = ALIGN(size, KMSAN_ORIGIN_SIZE); 223 origin_start = 224 (u32 *)kmsan_get_metadata((void *)address, KMSAN_META_ORIGIN); 225 226 /* 227 * If the new origin is non-zero, assume that the shadow byte is also non-zero, 228 * and unconditionally overwrite the old origin slot. 229 * If the new origin is zero, overwrite the old origin slot iff the 230 * corresponding shadow slot is zero. 231 */ 232 for (int i = 0; i < size / KMSAN_ORIGIN_SIZE; i++) { 233 if (origin || !shadow_start[i]) 234 origin_start[i] = origin; 235 } 236 } 237 238 struct page *kmsan_vmalloc_to_page_or_null(void *vaddr) 239 { 240 struct page *page; 241 242 if (!kmsan_internal_is_vmalloc_addr(vaddr) && 243 !kmsan_internal_is_module_addr(vaddr)) 244 return NULL; 245 page = vmalloc_to_page(vaddr); 246 if (pfn_valid(page_to_pfn(page))) 247 return page; 248 else 249 return NULL; 250 } 251 252 void kmsan_internal_check_memory(void *addr, size_t size, 253 const void __user *user_addr, int reason) 254 { 255 depot_stack_handle_t cur_origin = 0, new_origin = 0; 256 unsigned long addr64 = (unsigned long)addr; 257 depot_stack_handle_t *origin = NULL; 258 unsigned char *shadow = NULL; 259 int cur_off_start = -1; 260 int chunk_size; 261 size_t pos = 0; 262 263 if (!size) 264 return; 265 KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size)); 266 while (pos < size) { 267 chunk_size = min(size - pos, 268 PAGE_SIZE - ((addr64 + pos) % PAGE_SIZE)); 269 shadow = kmsan_get_metadata((void *)(addr64 + pos), 270 KMSAN_META_SHADOW); 271 if (!shadow) { 272 /* 273 * This page is untracked. If there were uninitialized 274 * bytes before, report them. 275 */ 276 if (cur_origin) { 277 kmsan_enter_runtime(); 278 kmsan_report(cur_origin, addr, size, 279 cur_off_start, pos - 1, user_addr, 280 reason); 281 kmsan_leave_runtime(); 282 } 283 cur_origin = 0; 284 cur_off_start = -1; 285 pos += chunk_size; 286 continue; 287 } 288 for (int i = 0; i < chunk_size; i++) { 289 if (!shadow[i]) { 290 /* 291 * This byte is unpoisoned. If there were 292 * poisoned bytes before, report them. 293 */ 294 if (cur_origin) { 295 kmsan_enter_runtime(); 296 kmsan_report(cur_origin, addr, size, 297 cur_off_start, pos + i - 1, 298 user_addr, reason); 299 kmsan_leave_runtime(); 300 } 301 cur_origin = 0; 302 cur_off_start = -1; 303 continue; 304 } 305 origin = kmsan_get_metadata((void *)(addr64 + pos + i), 306 KMSAN_META_ORIGIN); 307 KMSAN_WARN_ON(!origin); 308 new_origin = *origin; 309 /* 310 * Encountered new origin - report the previous 311 * uninitialized range. 312 */ 313 if (cur_origin != new_origin) { 314 if (cur_origin) { 315 kmsan_enter_runtime(); 316 kmsan_report(cur_origin, addr, size, 317 cur_off_start, pos + i - 1, 318 user_addr, reason); 319 kmsan_leave_runtime(); 320 } 321 cur_origin = new_origin; 322 cur_off_start = pos + i; 323 } 324 } 325 pos += chunk_size; 326 } 327 KMSAN_WARN_ON(pos != size); 328 if (cur_origin) { 329 kmsan_enter_runtime(); 330 kmsan_report(cur_origin, addr, size, cur_off_start, pos - 1, 331 user_addr, reason); 332 kmsan_leave_runtime(); 333 } 334 } 335 336 bool kmsan_metadata_is_contiguous(void *addr, size_t size) 337 { 338 char *cur_shadow = NULL, *next_shadow = NULL, *cur_origin = NULL, 339 *next_origin = NULL; 340 u64 cur_addr = (u64)addr, next_addr = cur_addr + PAGE_SIZE; 341 depot_stack_handle_t *origin_p; 342 bool all_untracked = false; 343 344 if (!size) 345 return true; 346 347 /* The whole range belongs to the same page. */ 348 if (ALIGN_DOWN(cur_addr + size - 1, PAGE_SIZE) == 349 ALIGN_DOWN(cur_addr, PAGE_SIZE)) 350 return true; 351 352 cur_shadow = kmsan_get_metadata((void *)cur_addr, /*is_origin*/ false); 353 if (!cur_shadow) 354 all_untracked = true; 355 cur_origin = kmsan_get_metadata((void *)cur_addr, /*is_origin*/ true); 356 if (all_untracked && cur_origin) 357 goto report; 358 359 for (; next_addr < (u64)addr + size; 360 cur_addr = next_addr, cur_shadow = next_shadow, 361 cur_origin = next_origin, next_addr += PAGE_SIZE) { 362 next_shadow = kmsan_get_metadata((void *)next_addr, false); 363 next_origin = kmsan_get_metadata((void *)next_addr, true); 364 if (all_untracked) { 365 if (next_shadow || next_origin) 366 goto report; 367 if (!next_shadow && !next_origin) 368 continue; 369 } 370 if (((u64)cur_shadow == ((u64)next_shadow - PAGE_SIZE)) && 371 ((u64)cur_origin == ((u64)next_origin - PAGE_SIZE))) 372 continue; 373 goto report; 374 } 375 return true; 376 377 report: 378 pr_err("%s: attempting to access two shadow page ranges.\n", __func__); 379 pr_err("Access of size %ld at %px.\n", size, addr); 380 pr_err("Addresses belonging to different ranges: %px and %px\n", 381 (void *)cur_addr, (void *)next_addr); 382 pr_err("page[0].shadow: %px, page[1].shadow: %px\n", cur_shadow, 383 next_shadow); 384 pr_err("page[0].origin: %px, page[1].origin: %px\n", cur_origin, 385 next_origin); 386 origin_p = kmsan_get_metadata(addr, KMSAN_META_ORIGIN); 387 if (origin_p) { 388 pr_err("Origin: %08x\n", *origin_p); 389 kmsan_print_origin(*origin_p); 390 } else { 391 pr_err("Origin: unavailable\n"); 392 } 393 return false; 394 } 395