libsanitizer/asan/asan_poisoning.cpp

   1 //===-- asan_poisoning.cpp ------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file is a part of AddressSanitizer, an address sanity checker.
  10 //
  11 // Shadow memory poisoning by ASan RTL and by user application.
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "asan_poisoning.h"
  15 #include "asan_report.h"
  16 #include "asan_stack.h"
  17 #include "sanitizer_common/sanitizer_atomic.h"
  18 #include "sanitizer_common/sanitizer_libc.h"
  19 #include "sanitizer_common/sanitizer_flags.h"
  20
  21 namespace __asan {
  22
  23 static atomic_uint8_t can_poison_memory;
  24
  25 void SetCanPoisonMemory(bool value) {
  26   atomic_store(&can_poison_memory, value, memory_order_release);
  27 }
  28
  29 bool CanPoisonMemory() {
  30   return atomic_load(&can_poison_memory, memory_order_acquire);
  31 }
  32
  33 void PoisonShadow(uptr addr, uptr size, u8 value) {
  34   if (value && !CanPoisonMemory()) return;
  35   CHECK(AddrIsAlignedByGranularity(addr));
  36   CHECK(AddrIsInMem(addr));
  37   CHECK(AddrIsAlignedByGranularity(addr + size));
  38   CHECK(AddrIsInMem(addr + size - SHADOW_GRANULARITY));
  39   CHECK(REAL(memset));
  40   FastPoisonShadow(addr, size, value);
  41 }
  42
  43 void PoisonShadowPartialRightRedzone(uptr addr,
  44                                      uptr size,
  45                                      uptr redzone_size,
  46                                      u8 value) {
  47   if (!CanPoisonMemory()) return;
  48   CHECK(AddrIsAlignedByGranularity(addr));
  49   CHECK(AddrIsInMem(addr));
  50   FastPoisonShadowPartialRightRedzone(addr, size, redzone_size, value);
  51 }
  52
  53 struct ShadowSegmentEndpoint {
  54   u8 *chunk;
  55   s8 offset;  // in [0, SHADOW_GRANULARITY)
  56   s8 value;  // = *chunk;
  57
  58   explicit ShadowSegmentEndpoint(uptr address) {
  59     chunk = (u8*)MemToShadow(address);
  60     offset = address & (SHADOW_GRANULARITY - 1);
  61     value = *chunk;
  62   }
  63 };
  64
  65 void AsanPoisonOrUnpoisonIntraObjectRedzone(uptr ptr, uptr size, bool poison) {
  66   uptr end = ptr + size;
  67   if (Verbosity()) {
  68     Printf("__asan_%spoison_intra_object_redzone [%p,%p) %zd\n",
  69            poison ? "" : "un", (void *)ptr, (void *)end, size);
  70     if (Verbosity() >= 2)
  71       PRINT_CURRENT_STACK();
  72   }
  73   CHECK(size);
  74   CHECK_LE(size, 4096);
  75   CHECK(IsAligned(end, SHADOW_GRANULARITY));
  76   if (!IsAligned(ptr, SHADOW_GRANULARITY)) {
  77     *(u8 *)MemToShadow(ptr) =
  78         poison ? static_cast<u8>(ptr % SHADOW_GRANULARITY) : 0;
  79     ptr |= SHADOW_GRANULARITY - 1;
  80     ptr++;
  81   }
  82   for (; ptr < end; ptr += SHADOW_GRANULARITY)
  83     *(u8*)MemToShadow(ptr) = poison ? kAsanIntraObjectRedzone : 0;
  84 }
  85
  86 }  // namespace __asan
  87
  88 // ---------------------- Interface ---------------- {{{1
  89 using namespace __asan;
  90
  91 // Current implementation of __asan_(un)poison_memory_region doesn't check
  92 // that user program (un)poisons the memory it owns. It poisons memory
  93 // conservatively, and unpoisons progressively to make sure asan shadow
  94 // mapping invariant is preserved (see detailed mapping description here:
  95 // https://github.com/google/sanitizers/wiki/AddressSanitizerAlgorithm).
  96 //
  97 // * if user asks to poison region [left, right), the program poisons
  98 // at least [left, AlignDown(right)).
  99 // * if user asks to unpoison region [left, right), the program unpoisons
 100 // at most [AlignDown(left), right).
 101 void __asan_poison_memory_region(void const volatile *addr, uptr size) {
 102   if (!flags()->allow_user_poisoning || size == 0) return;
 103   uptr beg_addr = (uptr)addr;
 104   uptr end_addr = beg_addr + size;
 105   VPrintf(3, "Trying to poison memory region [%p, %p)\n", (void *)beg_addr,
 106           (void *)end_addr);
 107   ShadowSegmentEndpoint beg(beg_addr);
 108   ShadowSegmentEndpoint end(end_addr);
 109   if (beg.chunk == end.chunk) {
 110     CHECK_LT(beg.offset, end.offset);
 111     s8 value = beg.value;
 112     CHECK_EQ(value, end.value);
 113     // We can only poison memory if the byte in end.offset is unaddressable.
 114     // No need to re-poison memory if it is poisoned already.
 115     if (value > 0 && value <= end.offset) {
 116       if (beg.offset > 0) {
 117         *beg.chunk = Min(value, beg.offset);
 118       } else {
 119         *beg.chunk = kAsanUserPoisonedMemoryMagic;
 120       }
 121     }
 122     return;
 123   }
 124   CHECK_LT(beg.chunk, end.chunk);
 125   if (beg.offset > 0) {
 126     // Mark bytes from beg.offset as unaddressable.
 127     if (beg.value == 0) {
 128       *beg.chunk = beg.offset;
 129     } else {
 130       *beg.chunk = Min(beg.value, beg.offset);
 131     }
 132     beg.chunk++;
 133   }
 134   REAL(memset)(beg.chunk, kAsanUserPoisonedMemoryMagic, end.chunk - beg.chunk);
 135   // Poison if byte in end.offset is unaddressable.
 136   if (end.value > 0 && end.value <= end.offset) {
 137     *end.chunk = kAsanUserPoisonedMemoryMagic;
 138   }
 139 }
 140
 141 void __asan_unpoison_memory_region(void const volatile *addr, uptr size) {
 142   if (!flags()->allow_user_poisoning || size == 0) return;
 143   uptr beg_addr = (uptr)addr;
 144   uptr end_addr = beg_addr + size;
 145   VPrintf(3, "Trying to unpoison memory region [%p, %p)\n", (void *)beg_addr,
 146           (void *)end_addr);
 147   ShadowSegmentEndpoint beg(beg_addr);
 148   ShadowSegmentEndpoint end(end_addr);
 149   if (beg.chunk == end.chunk) {
 150     CHECK_LT(beg.offset, end.offset);
 151     s8 value = beg.value;
 152     CHECK_EQ(value, end.value);
 153     // We unpoison memory bytes up to enbytes up to end.offset if it is not
 154     // unpoisoned already.
 155     if (value != 0) {
 156       *beg.chunk = Max(value, end.offset);
 157     }
 158     return;
 159   }
 160   CHECK_LT(beg.chunk, end.chunk);
 161   if (beg.offset > 0) {
 162     *beg.chunk = 0;
 163     beg.chunk++;
 164   }
 165   REAL(memset)(beg.chunk, 0, end.chunk - beg.chunk);
 166   if (end.offset > 0 && end.value != 0) {
 167     *end.chunk = Max(end.value, end.offset);
 168   }
 169 }
 170
 171 int __asan_address_is_poisoned(void const volatile *addr) {
 172   return __asan::AddressIsPoisoned((uptr)addr);
 173 }
 174
 175 uptr __asan_region_is_poisoned(uptr beg, uptr size) {
 176   if (!size)
 177     return 0;
 178   uptr end = beg + size;
 179   if (!AddrIsInMem(beg))
 180     return beg;
 181   if (!AddrIsInMem(end))
 182     return end;
 183   CHECK_LT(beg, end);
 184   uptr aligned_b = RoundUpTo(beg, SHADOW_GRANULARITY);
 185   uptr aligned_e = RoundDownTo(end, SHADOW_GRANULARITY);
 186   uptr shadow_beg = MemToShadow(aligned_b);
 187   uptr shadow_end = MemToShadow(aligned_e);
 188   // First check the first and the last application bytes,
 189   // then check the SHADOW_GRANULARITY-aligned region by calling
 190   // mem_is_zero on the corresponding shadow.
 191   if (!__asan::AddressIsPoisoned(beg) && !__asan::AddressIsPoisoned(end - 1) &&
 192       (shadow_end <= shadow_beg ||
 193        __sanitizer::mem_is_zero((const char *)shadow_beg,
 194                                 shadow_end - shadow_beg)))
 195     return 0;
 196   // The fast check failed, so we have a poisoned byte somewhere.
 197   // Find it slowly.
 198   for (; beg < end; beg++)
 199     if (__asan::AddressIsPoisoned(beg))
 200       return beg;
 201   UNREACHABLE("mem_is_zero returned false, but poisoned byte was not found");
 202   return 0;
 203 }
 204
 205 #define CHECK_SMALL_REGION(p, size, isWrite)                  \
 206   do {                                                        \
 207     uptr __p = reinterpret_cast<uptr>(p);                     \
 208     uptr __size = size;                                       \
 209     if (UNLIKELY(__asan::AddressIsPoisoned(__p) ||            \
 210         __asan::AddressIsPoisoned(__p + __size - 1))) {       \
 211       GET_CURRENT_PC_BP_SP;                                   \
 212       uptr __bad = __asan_region_is_poisoned(__p, __size);    \
 213       __asan_report_error(pc, bp, sp, __bad, isWrite, __size, 0);\
 214     }                                                         \
 215   } while (false)
 216
 217
 218 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 219 u16 __sanitizer_unaligned_load16(const uu16 *p) {
 220   CHECK_SMALL_REGION(p, sizeof(*p), false);
 221   return *p;
 222 }
 223
 224 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 225 u32 __sanitizer_unaligned_load32(const uu32 *p) {
 226   CHECK_SMALL_REGION(p, sizeof(*p), false);
 227   return *p;
 228 }
 229
 230 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 231 u64 __sanitizer_unaligned_load64(const uu64 *p) {
 232   CHECK_SMALL_REGION(p, sizeof(*p), false);
 233   return *p;
 234 }
 235
 236 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 237 void __sanitizer_unaligned_store16(uu16 *p, u16 x) {
 238   CHECK_SMALL_REGION(p, sizeof(*p), true);
 239   *p = x;
 240 }
 241
 242 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 243 void __sanitizer_unaligned_store32(uu32 *p, u32 x) {
 244   CHECK_SMALL_REGION(p, sizeof(*p), true);
 245   *p = x;
 246 }
 247
 248 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 249 void __sanitizer_unaligned_store64(uu64 *p, u64 x) {
 250   CHECK_SMALL_REGION(p, sizeof(*p), true);
 251   *p = x;
 252 }
 253
 254 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 255 void __asan_poison_cxx_array_cookie(uptr p) {
 256   if (SANITIZER_WORDSIZE != 64) return;
 257   if (!flags()->poison_array_cookie) return;
 258   uptr s = MEM_TO_SHADOW(p);
 259   *reinterpret_cast<u8*>(s) = kAsanArrayCookieMagic;
 260 }
 261
 262 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 263 uptr __asan_load_cxx_array_cookie(uptr *p) {
 264   if (SANITIZER_WORDSIZE != 64) return *p;
 265   if (!flags()->poison_array_cookie) return *p;
 266   uptr s = MEM_TO_SHADOW(reinterpret_cast<uptr>(p));
 267   u8 sval = *reinterpret_cast<u8*>(s);
 268   if (sval == kAsanArrayCookieMagic) return *p;
 269   // If sval is not kAsanArrayCookieMagic it can only be freed memory,
 270   // which means that we are going to get double-free. So, return 0 to avoid
 271   // infinite loop of destructors. We don't want to report a double-free here
 272   // though, so print a warning just in case.
 273   // CHECK_EQ(sval, kAsanHeapFreeMagic);
 274   if (sval == kAsanHeapFreeMagic) {
 275     Report("AddressSanitizer: loaded array cookie from free-d memory; "
 276            "expect a double-free report\n");
 277     return 0;
 278   }
 279   // The cookie may remain unpoisoned if e.g. it comes from a custom
 280   // operator new defined inside a class.
 281   return *p;
 282 }
 283
 284 // This is a simplified version of __asan_(un)poison_memory_region, which
 285 // assumes that left border of region to be poisoned is properly aligned.
 286 static void PoisonAlignedStackMemory(uptr addr, uptr size, bool do_poison) {
 287   if (size == 0) return;
 288   uptr aligned_size = size & ~(SHADOW_GRANULARITY - 1);
 289   PoisonShadow(addr, aligned_size,
 290                do_poison ? kAsanStackUseAfterScopeMagic : 0);
 291   if (size == aligned_size)
 292     return;
 293   s8 end_offset = (s8)(size - aligned_size);
 294   s8* shadow_end = (s8*)MemToShadow(addr + aligned_size);
 295   s8 end_value = *shadow_end;
 296   if (do_poison) {
 297     // If possible, mark all the bytes mapping to last shadow byte as
 298     // unaddressable.
 299     if (end_value > 0 && end_value <= end_offset)
 300       *shadow_end = (s8)kAsanStackUseAfterScopeMagic;
 301   } else {
 302     // If necessary, mark few first bytes mapping to last shadow byte
 303     // as addressable
 304     if (end_value != 0)
 305       *shadow_end = Max(end_value, end_offset);
 306   }
 307 }
 308
 309 void __asan_set_shadow_00(uptr addr, uptr size) {
 310   REAL(memset)((void *)addr, 0, size);
 311 }
 312
 313 void __asan_set_shadow_f1(uptr addr, uptr size) {
 314   REAL(memset)((void *)addr, 0xf1, size);
 315 }
 316
 317 void __asan_set_shadow_f2(uptr addr, uptr size) {
 318   REAL(memset)((void *)addr, 0xf2, size);
 319 }
 320
 321 void __asan_set_shadow_f3(uptr addr, uptr size) {
 322   REAL(memset)((void *)addr, 0xf3, size);
 323 }
 324
 325 void __asan_set_shadow_f5(uptr addr, uptr size) {
 326   REAL(memset)((void *)addr, 0xf5, size);
 327 }
 328
 329 void __asan_set_shadow_f8(uptr addr, uptr size) {
 330   REAL(memset)((void *)addr, 0xf8, size);
 331 }
 332
 333 void __asan_poison_stack_memory(uptr addr, uptr size) {
 334   VReport(1, "poisoning: %p %zx\n", (void *)addr, size);
 335   PoisonAlignedStackMemory(addr, size, true);
 336 }
 337
 338 void __asan_unpoison_stack_memory(uptr addr, uptr size) {
 339   VReport(1, "unpoisoning: %p %zx\n", (void *)addr, size);
 340   PoisonAlignedStackMemory(addr, size, false);
 341 }
 342
 343 void __sanitizer_annotate_contiguous_container(const void *beg_p,
 344                                                const void *end_p,
 345                                                const void *old_mid_p,
 346                                                const void *new_mid_p) {
 347   if (!flags()->detect_container_overflow) return;
 348   VPrintf(2, "contiguous_container: %p %p %p %p\n", beg_p, end_p, old_mid_p,
 349           new_mid_p);
 350   uptr beg = reinterpret_cast<uptr>(beg_p);
 351   uptr end = reinterpret_cast<uptr>(end_p);
 352   uptr old_mid = reinterpret_cast<uptr>(old_mid_p);
 353   uptr new_mid = reinterpret_cast<uptr>(new_mid_p);
 354   uptr granularity = SHADOW_GRANULARITY;
 355   if (!(beg <= old_mid && beg <= new_mid && old_mid <= end && new_mid <= end &&
 356         IsAligned(beg, granularity))) {
 357     GET_STACK_TRACE_FATAL_HERE;
 358     ReportBadParamsToAnnotateContiguousContainer(beg, end, old_mid, new_mid,
 359                                                  &stack);
 360   }
 361   CHECK_LE(end - beg,
 362            FIRST_32_SECOND_64(1UL << 30, 1ULL << 40)); // Sanity check.
 363
 364   uptr a = RoundDownTo(Min(old_mid, new_mid), granularity);
 365   uptr c = RoundUpTo(Max(old_mid, new_mid), granularity);
 366   uptr d1 = RoundDownTo(old_mid, granularity);
 367   // uptr d2 = RoundUpTo(old_mid, granularity);
 368   // Currently we should be in this state:
 369   // [a, d1) is good, [d2, c) is bad, [d1, d2) is partially good.
 370   // Make a quick sanity check that we are indeed in this state.
 371   //
 372   // FIXME: Two of these three checks are disabled until we fix
 373   // https://github.com/google/sanitizers/issues/258.
 374   // if (d1 != d2)
 375   //  CHECK_EQ(*(u8*)MemToShadow(d1), old_mid - d1);
 376   if (a + granularity <= d1)
 377     CHECK_EQ(*(u8*)MemToShadow(a), 0);
 378   // if (d2 + granularity <= c && c <= end)
 379   //   CHECK_EQ(*(u8 *)MemToShadow(c - granularity),
 380   //            kAsanContiguousContainerOOBMagic);
 381
 382   uptr b1 = RoundDownTo(new_mid, granularity);
 383   uptr b2 = RoundUpTo(new_mid, granularity);
 384   // New state:
 385   // [a, b1) is good, [b2, c) is bad, [b1, b2) is partially good.
 386   PoisonShadow(a, b1 - a, 0);
 387   PoisonShadow(b2, c - b2, kAsanContiguousContainerOOBMagic);
 388   if (b1 != b2) {
 389     CHECK_EQ(b2 - b1, granularity);
 390     *(u8*)MemToShadow(b1) = static_cast<u8>(new_mid - b1);
 391   }
 392 }
 393
 394 const void *__sanitizer_contiguous_container_find_bad_address(
 395     const void *beg_p, const void *mid_p, const void *end_p) {
 396   if (!flags()->detect_container_overflow)
 397     return nullptr;
 398   uptr beg = reinterpret_cast<uptr>(beg_p);
 399   uptr end = reinterpret_cast<uptr>(end_p);
 400   uptr mid = reinterpret_cast<uptr>(mid_p);
 401   CHECK_LE(beg, mid);
 402   CHECK_LE(mid, end);
 403   // Check some bytes starting from beg, some bytes around mid, and some bytes
 404   // ending with end.
 405   uptr kMaxRangeToCheck = 32;
 406   uptr r1_beg = beg;
 407   uptr r1_end = Min(beg + kMaxRangeToCheck, mid);
 408   uptr r2_beg = Max(beg, mid - kMaxRangeToCheck);
 409   uptr r2_end = Min(end, mid + kMaxRangeToCheck);
 410   uptr r3_beg = Max(end - kMaxRangeToCheck, mid);
 411   uptr r3_end = end;
 412   for (uptr i = r1_beg; i < r1_end; i++)
 413     if (AddressIsPoisoned(i))
 414       return reinterpret_cast<const void *>(i);
 415   for (uptr i = r2_beg; i < mid; i++)
 416     if (AddressIsPoisoned(i))
 417       return reinterpret_cast<const void *>(i);
 418   for (uptr i = mid; i < r2_end; i++)
 419     if (!AddressIsPoisoned(i))
 420       return reinterpret_cast<const void *>(i);
 421   for (uptr i = r3_beg; i < r3_end; i++)
 422     if (!AddressIsPoisoned(i))
 423       return reinterpret_cast<const void *>(i);
 424   return nullptr;
 425 }
 426
 427 int __sanitizer_verify_contiguous_container(const void *beg_p,
 428                                             const void *mid_p,
 429                                             const void *end_p) {
 430   return __sanitizer_contiguous_container_find_bad_address(beg_p, mid_p,
 431                                                            end_p) == nullptr;
 432 }
 433
 434 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 435 void __asan_poison_intra_object_redzone(uptr ptr, uptr size) {
 436   AsanPoisonOrUnpoisonIntraObjectRedzone(ptr, size, true);
 437 }
 438
 439 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 440 void __asan_unpoison_intra_object_redzone(uptr ptr, uptr size) {
 441   AsanPoisonOrUnpoisonIntraObjectRedzone(ptr, size, false);
 442 }
 443
 444 // --- Implementation of LSan-specific functions --- {{{1
 445 namespace __lsan {
 446 bool WordIsPoisoned(uptr addr) {
 447   return (__asan_region_is_poisoned(addr, sizeof(uptr)) != 0);
 448 }
 449 }