libsanitizer/asan/asan_fake_stack.cpp

   1 //===-- asan_fake_stack.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 // FakeStack is used to detect use-after-return bugs.
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "asan_allocator.h"
  15 #include "asan_poisoning.h"
  16 #include "asan_thread.h"
  17
  18 namespace __asan {
  19
  20 static const u64 kMagic1 = kAsanStackAfterReturnMagic;
  21 static const u64 kMagic2 = (kMagic1 << 8) | kMagic1;
  22 static const u64 kMagic4 = (kMagic2 << 16) | kMagic2;
  23 static const u64 kMagic8 = (kMagic4 << 32) | kMagic4;
  24
  25 static const u64 kAllocaRedzoneSize = 32UL;
  26 static const u64 kAllocaRedzoneMask = 31UL;
  27
  28 // For small size classes inline PoisonShadow for better performance.
  29 ALWAYS_INLINE void SetShadow(uptr ptr, uptr size, uptr class_id, u64 magic) {
  30   u64 *shadow = reinterpret_cast<u64*>(MemToShadow(ptr));
  31   if (SHADOW_SCALE == 3 && class_id <= 6) {
  32     // This code expects SHADOW_SCALE=3.
  33     for (uptr i = 0; i < (((uptr)1) << class_id); i++) {
  34       shadow[i] = magic;
  35       // Make sure this does not become memset.
  36       SanitizerBreakOptimization(nullptr);
  37     }
  38   } else {
  39     // The size class is too big, it's cheaper to poison only size bytes.
  40     PoisonShadow(ptr, size, static_cast<u8>(magic));
  41   }
  42 }
  43
  44 FakeStack *FakeStack::Create(uptr stack_size_log) {
  45   static uptr kMinStackSizeLog = 16;
  46   static uptr kMaxStackSizeLog = FIRST_32_SECOND_64(24, 28);
  47   if (stack_size_log < kMinStackSizeLog)
  48     stack_size_log = kMinStackSizeLog;
  49   if (stack_size_log > kMaxStackSizeLog)
  50     stack_size_log = kMaxStackSizeLog;
  51   uptr size = RequiredSize(stack_size_log);
  52   FakeStack *res = reinterpret_cast<FakeStack *>(
  53       flags()->uar_noreserve ? MmapNoReserveOrDie(size, "FakeStack")
  54                              : MmapOrDie(size, "FakeStack"));
  55   res->stack_size_log_ = stack_size_log;
  56   u8 *p = reinterpret_cast<u8 *>(res);
  57   VReport(1,
  58           "T%d: FakeStack created: %p -- %p stack_size_log: %zd; "
  59           "mmapped %zdK, noreserve=%d \n",
  60           GetCurrentTidOrInvalid(), (void *)p,
  61           (void *)(p + FakeStack::RequiredSize(stack_size_log)), stack_size_log,
  62           size >> 10, flags()->uar_noreserve);
  63   return res;
  64 }
  65
  66 void FakeStack::Destroy(int tid) {
  67   PoisonAll(0);
  68   if (Verbosity() >= 2) {
  69     InternalScopedString str;
  70     for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++)
  71       str.append("%zd: %zd/%zd; ", class_id, hint_position_[class_id],
  72                  NumberOfFrames(stack_size_log(), class_id));
  73     Report("T%d: FakeStack destroyed: %s\n", tid, str.data());
  74   }
  75   uptr size = RequiredSize(stack_size_log_);
  76   FlushUnneededASanShadowMemory(reinterpret_cast<uptr>(this), size);
  77   UnmapOrDie(this, size);
  78 }
  79
  80 void FakeStack::PoisonAll(u8 magic) {
  81   PoisonShadow(reinterpret_cast<uptr>(this), RequiredSize(stack_size_log()),
  82                magic);
  83 }
  84
  85 #if !defined(_MSC_VER) || defined(__clang__)
  86 ALWAYS_INLINE USED
  87 #endif
  88 FakeFrame *FakeStack::Allocate(uptr stack_size_log, uptr class_id,
  89                                uptr real_stack) {
  90   CHECK_LT(class_id, kNumberOfSizeClasses);
  91   if (needs_gc_)
  92     GC(real_stack);
  93   uptr &hint_position = hint_position_[class_id];
  94   const int num_iter = NumberOfFrames(stack_size_log, class_id);
  95   u8 *flags = GetFlags(stack_size_log, class_id);
  96   for (int i = 0; i < num_iter; i++) {
  97     uptr pos = ModuloNumberOfFrames(stack_size_log, class_id, hint_position++);
  98     // This part is tricky. On one hand, checking and setting flags[pos]
  99     // should be atomic to ensure async-signal safety. But on the other hand,
 100     // if the signal arrives between checking and setting flags[pos], the
 101     // signal handler's fake stack will start from a different hint_position
 102     // and so will not touch this particular byte. So, it is safe to do this
 103     // with regular non-atomic load and store (at least I was not able to make
 104     // this code crash).
 105     if (flags[pos]) continue;
 106     flags[pos] = 1;
 107     FakeFrame *res = reinterpret_cast<FakeFrame *>(
 108         GetFrame(stack_size_log, class_id, pos));
 109     res->real_stack = real_stack;
 110     *SavedFlagPtr(reinterpret_cast<uptr>(res), class_id) = &flags[pos];
 111     return res;
 112   }
 113   return nullptr; // We are out of fake stack.
 114 }
 115
 116 uptr FakeStack::AddrIsInFakeStack(uptr ptr, uptr *frame_beg, uptr *frame_end) {
 117   uptr stack_size_log = this->stack_size_log();
 118   uptr beg = reinterpret_cast<uptr>(GetFrame(stack_size_log, 0, 0));
 119   uptr end = reinterpret_cast<uptr>(this) + RequiredSize(stack_size_log);
 120   if (ptr < beg || ptr >= end) return 0;
 121   uptr class_id = (ptr - beg) >> stack_size_log;
 122   uptr base = beg + (class_id << stack_size_log);
 123   CHECK_LE(base, ptr);
 124   CHECK_LT(ptr, base + (((uptr)1) << stack_size_log));
 125   uptr pos = (ptr - base) >> (kMinStackFrameSizeLog + class_id);
 126   uptr res = base + pos * BytesInSizeClass(class_id);
 127   *frame_end = res + BytesInSizeClass(class_id);
 128   *frame_beg = res + sizeof(FakeFrame);
 129   return res;
 130 }
 131
 132 void FakeStack::HandleNoReturn() {
 133   needs_gc_ = true;
 134 }
 135
 136 // When throw, longjmp or some such happens we don't call OnFree() and
 137 // as the result may leak one or more fake frames, but the good news is that
 138 // we are notified about all such events by HandleNoReturn().
 139 // If we recently had such no-return event we need to collect garbage frames.
 140 // We do it based on their 'real_stack' values -- everything that is lower
 141 // than the current real_stack is garbage.
 142 NOINLINE void FakeStack::GC(uptr real_stack) {
 143   uptr collected = 0;
 144   for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++) {
 145     u8 *flags = GetFlags(stack_size_log(), class_id);
 146     for (uptr i = 0, n = NumberOfFrames(stack_size_log(), class_id); i < n;
 147          i++) {
 148       if (flags[i] == 0) continue;  // not allocated.
 149       FakeFrame *ff = reinterpret_cast<FakeFrame *>(
 150           GetFrame(stack_size_log(), class_id, i));
 151       if (ff->real_stack < real_stack) {
 152         flags[i] = 0;
 153         collected++;
 154       }
 155     }
 156   }
 157   needs_gc_ = false;
 158 }
 159
 160 void FakeStack::ForEachFakeFrame(RangeIteratorCallback callback, void *arg) {
 161   for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++) {
 162     u8 *flags = GetFlags(stack_size_log(), class_id);
 163     for (uptr i = 0, n = NumberOfFrames(stack_size_log(), class_id); i < n;
 164          i++) {
 165       if (flags[i] == 0) continue;  // not allocated.
 166       FakeFrame *ff = reinterpret_cast<FakeFrame *>(
 167           GetFrame(stack_size_log(), class_id, i));
 168       uptr begin = reinterpret_cast<uptr>(ff);
 169       callback(begin, begin + FakeStack::BytesInSizeClass(class_id), arg);
 170     }
 171   }
 172 }
 173
 174 #if (SANITIZER_LINUX && !SANITIZER_ANDROID) || SANITIZER_FUCHSIA
 175 static THREADLOCAL FakeStack *fake_stack_tls;
 176
 177 FakeStack *GetTLSFakeStack() {
 178   return fake_stack_tls;
 179 }
 180 void SetTLSFakeStack(FakeStack *fs) {
 181   fake_stack_tls = fs;
 182 }
 183 #else
 184 FakeStack *GetTLSFakeStack() { return 0; }
 185 void SetTLSFakeStack(FakeStack *fs) { }
 186 #endif  // (SANITIZER_LINUX && !SANITIZER_ANDROID) || SANITIZER_FUCHSIA
 187
 188 static FakeStack *GetFakeStack() {
 189   AsanThread *t = GetCurrentThread();
 190   if (!t) return nullptr;
 191   return t->get_or_create_fake_stack();
 192 }
 193
 194 static FakeStack *GetFakeStackFast() {
 195   if (FakeStack *fs = GetTLSFakeStack())
 196     return fs;
 197   if (!__asan_option_detect_stack_use_after_return)
 198     return nullptr;
 199   return GetFakeStack();
 200 }
 201
 202 static FakeStack *GetFakeStackFastAlways() {
 203   if (FakeStack *fs = GetTLSFakeStack())
 204     return fs;
 205   return GetFakeStack();
 206 }
 207
 208 static ALWAYS_INLINE uptr OnMalloc(uptr class_id, uptr size) {
 209   FakeStack *fs = GetFakeStackFast();
 210   if (!fs) return 0;
 211   uptr local_stack;
 212   uptr real_stack = reinterpret_cast<uptr>(&local_stack);
 213   FakeFrame *ff = fs->Allocate(fs->stack_size_log(), class_id, real_stack);
 214   if (!ff) return 0;  // Out of fake stack.
 215   uptr ptr = reinterpret_cast<uptr>(ff);
 216   SetShadow(ptr, size, class_id, 0);
 217   return ptr;
 218 }
 219
 220 static ALWAYS_INLINE uptr OnMallocAlways(uptr class_id, uptr size) {
 221   FakeStack *fs = GetFakeStackFastAlways();
 222   if (!fs)
 223     return 0;
 224   uptr local_stack;
 225   uptr real_stack = reinterpret_cast<uptr>(&local_stack);
 226   FakeFrame *ff = fs->Allocate(fs->stack_size_log(), class_id, real_stack);
 227   if (!ff)
 228     return 0;  // Out of fake stack.
 229   uptr ptr = reinterpret_cast<uptr>(ff);
 230   SetShadow(ptr, size, class_id, 0);
 231   return ptr;
 232 }
 233
 234 static ALWAYS_INLINE void OnFree(uptr ptr, uptr class_id, uptr size) {
 235   FakeStack::Deallocate(ptr, class_id);
 236   SetShadow(ptr, size, class_id, kMagic8);
 237 }
 238
 239 } // namespace __asan
 240
 241 // ---------------------- Interface ---------------- {{{1
 242 using namespace __asan;
 243 #define DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(class_id)                      \
 244   extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr                               \
 245       __asan_stack_malloc_##class_id(uptr size) {                             \
 246     return OnMalloc(class_id, size);                                          \
 247   }                                                                           \
 248   extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr                               \
 249       __asan_stack_malloc_always_##class_id(uptr size) {                      \
 250     return OnMallocAlways(class_id, size);                                    \
 251   }                                                                           \
 252   extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __asan_stack_free_##class_id( \
 253       uptr ptr, uptr size) {                                                  \
 254     OnFree(ptr, class_id, size);                                              \
 255   }
 256
 257 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(0)
 258 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(1)
 259 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(2)
 260 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(3)
 261 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(4)
 262 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(5)
 263 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(6)
 264 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(7)
 265 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(8)
 266 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(9)
 267 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(10)
 268
 269 extern "C" {
 270 // TODO: remove this method and fix tests that use it by setting
 271 // -asan-use-after-return=never, after modal UAR flag lands
 272 // (https://github.com/google/sanitizers/issues/1394)
 273 SANITIZER_INTERFACE_ATTRIBUTE
 274 void *__asan_get_current_fake_stack() { return GetFakeStackFast(); }
 275
 276 SANITIZER_INTERFACE_ATTRIBUTE
 277 void *__asan_addr_is_in_fake_stack(void *fake_stack, void *addr, void **beg,
 278                                    void **end) {
 279   FakeStack *fs = reinterpret_cast<FakeStack*>(fake_stack);
 280   if (!fs) return nullptr;
 281   uptr frame_beg, frame_end;
 282   FakeFrame *frame = reinterpret_cast<FakeFrame *>(fs->AddrIsInFakeStack(
 283       reinterpret_cast<uptr>(addr), &frame_beg, &frame_end));
 284   if (!frame) return nullptr;
 285   if (frame->magic != kCurrentStackFrameMagic)
 286     return nullptr;
 287   if (beg) *beg = reinterpret_cast<void*>(frame_beg);
 288   if (end) *end = reinterpret_cast<void*>(frame_end);
 289   return reinterpret_cast<void*>(frame->real_stack);
 290 }
 291
 292 SANITIZER_INTERFACE_ATTRIBUTE
 293 void __asan_alloca_poison(uptr addr, uptr size) {
 294   uptr LeftRedzoneAddr = addr - kAllocaRedzoneSize;
 295   uptr PartialRzAddr = addr + size;
 296   uptr RightRzAddr = (PartialRzAddr + kAllocaRedzoneMask) & ~kAllocaRedzoneMask;
 297   uptr PartialRzAligned = PartialRzAddr & ~(SHADOW_GRANULARITY - 1);
 298   FastPoisonShadow(LeftRedzoneAddr, kAllocaRedzoneSize, kAsanAllocaLeftMagic);
 299   FastPoisonShadowPartialRightRedzone(
 300       PartialRzAligned, PartialRzAddr % SHADOW_GRANULARITY,
 301       RightRzAddr - PartialRzAligned, kAsanAllocaRightMagic);
 302   FastPoisonShadow(RightRzAddr, kAllocaRedzoneSize, kAsanAllocaRightMagic);
 303 }
 304
 305 SANITIZER_INTERFACE_ATTRIBUTE
 306 void __asan_allocas_unpoison(uptr top, uptr bottom) {
 307   if ((!top) || (top > bottom)) return;
 308   REAL(memset)(reinterpret_cast<void*>(MemToShadow(top)), 0,
 309                (bottom - top) / SHADOW_GRANULARITY);
 310 }
 311 } // extern "C"