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, "T%d: FakeStack created: %p -- %p stack_size_log: %zd; "
  58           "mmapped %zdK, noreserve=%d \n",
  59           GetCurrentTidOrInvalid(), p,
  60           p + FakeStack::RequiredSize(stack_size_log), stack_size_log,
  61           size >> 10, flags()->uar_noreserve);
  62   return res;
  63 }
  64
  65 void FakeStack::Destroy(int tid) {
  66   PoisonAll(0);
  67   if (Verbosity() >= 2) {
  68     InternalScopedString str;
  69     for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++)
  70       str.append("%zd: %zd/%zd; ", class_id, hint_position_[class_id],
  71                  NumberOfFrames(stack_size_log(), class_id));
  72     Report("T%d: FakeStack destroyed: %s\n", tid, str.data());
  73   }
  74   uptr size = RequiredSize(stack_size_log_);
  75   FlushUnneededASanShadowMemory(reinterpret_cast<uptr>(this), size);
  76   UnmapOrDie(this, size);
  77 }
  78
  79 void FakeStack::PoisonAll(u8 magic) {
  80   PoisonShadow(reinterpret_cast<uptr>(this), RequiredSize(stack_size_log()),
  81                magic);
  82 }
  83
  84 #if !defined(_MSC_VER) || defined(__clang__)
  85 ALWAYS_INLINE USED
  86 #endif
  87 FakeFrame *FakeStack::Allocate(uptr stack_size_log, uptr class_id,
  88                                uptr real_stack) {
  89   CHECK_LT(class_id, kNumberOfSizeClasses);
  90   if (needs_gc_)
  91     GC(real_stack);
  92   uptr &hint_position = hint_position_[class_id];
  93   const int num_iter = NumberOfFrames(stack_size_log, class_id);
  94   u8 *flags = GetFlags(stack_size_log, class_id);
  95   for (int i = 0; i < num_iter; i++) {
  96     uptr pos = ModuloNumberOfFrames(stack_size_log, class_id, hint_position++);
  97     // This part is tricky. On one hand, checking and setting flags[pos]
  98     // should be atomic to ensure async-signal safety. But on the other hand,
  99     // if the signal arrives between checking and setting flags[pos], the
 100     // signal handler's fake stack will start from a different hint_position
 101     // and so will not touch this particular byte. So, it is safe to do this
 102     // with regular non-atomic load and store (at least I was not able to make
 103     // this code crash).
 104     if (flags[pos]) continue;
 105     flags[pos] = 1;
 106     FakeFrame *res = reinterpret_cast<FakeFrame *>(
 107         GetFrame(stack_size_log, class_id, pos));
 108     res->real_stack = real_stack;
 109     *SavedFlagPtr(reinterpret_cast<uptr>(res), class_id) = &flags[pos];
 110     return res;
 111   }
 112   return nullptr; // We are out of fake stack.
 113 }
 114
 115 uptr FakeStack::AddrIsInFakeStack(uptr ptr, uptr *frame_beg, uptr *frame_end) {
 116   uptr stack_size_log = this->stack_size_log();
 117   uptr beg = reinterpret_cast<uptr>(GetFrame(stack_size_log, 0, 0));
 118   uptr end = reinterpret_cast<uptr>(this) + RequiredSize(stack_size_log);
 119   if (ptr < beg || ptr >= end) return 0;
 120   uptr class_id = (ptr - beg) >> stack_size_log;
 121   uptr base = beg + (class_id << stack_size_log);
 122   CHECK_LE(base, ptr);
 123   CHECK_LT(ptr, base + (((uptr)1) << stack_size_log));
 124   uptr pos = (ptr - base) >> (kMinStackFrameSizeLog + class_id);
 125   uptr res = base + pos * BytesInSizeClass(class_id);
 126   *frame_end = res + BytesInSizeClass(class_id);
 127   *frame_beg = res + sizeof(FakeFrame);
 128   return res;
 129 }
 130
 131 void FakeStack::HandleNoReturn() {
 132   needs_gc_ = true;
 133 }
 134
 135 // When throw, longjmp or some such happens we don't call OnFree() and
 136 // as the result may leak one or more fake frames, but the good news is that
 137 // we are notified about all such events by HandleNoReturn().
 138 // If we recently had such no-return event we need to collect garbage frames.
 139 // We do it based on their 'real_stack' values -- everything that is lower
 140 // than the current real_stack is garbage.
 141 NOINLINE void FakeStack::GC(uptr real_stack) {
 142   uptr collected = 0;
 143   for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++) {
 144     u8 *flags = GetFlags(stack_size_log(), class_id);
 145     for (uptr i = 0, n = NumberOfFrames(stack_size_log(), class_id); i < n;
 146          i++) {
 147       if (flags[i] == 0) continue;  // not allocated.
 148       FakeFrame *ff = reinterpret_cast<FakeFrame *>(
 149           GetFrame(stack_size_log(), class_id, i));
 150       if (ff->real_stack < real_stack) {
 151         flags[i] = 0;
 152         collected++;
 153       }
 154     }
 155   }
 156   needs_gc_ = false;
 157 }
 158
 159 void FakeStack::ForEachFakeFrame(RangeIteratorCallback callback, void *arg) {
 160   for (uptr class_id = 0; class_id < kNumberOfSizeClasses; class_id++) {
 161     u8 *flags = GetFlags(stack_size_log(), class_id);
 162     for (uptr i = 0, n = NumberOfFrames(stack_size_log(), class_id); i < n;
 163          i++) {
 164       if (flags[i] == 0) continue;  // not allocated.
 165       FakeFrame *ff = reinterpret_cast<FakeFrame *>(
 166           GetFrame(stack_size_log(), class_id, i));
 167       uptr begin = reinterpret_cast<uptr>(ff);
 168       callback(begin, begin + FakeStack::BytesInSizeClass(class_id), arg);
 169     }
 170   }
 171 }
 172
 173 #if (SANITIZER_LINUX && !SANITIZER_ANDROID) || SANITIZER_FUCHSIA
 174 static THREADLOCAL FakeStack *fake_stack_tls;
 175
 176 FakeStack *GetTLSFakeStack() {
 177   return fake_stack_tls;
 178 }
 179 void SetTLSFakeStack(FakeStack *fs) {
 180   fake_stack_tls = fs;
 181 }
 182 #else
 183 FakeStack *GetTLSFakeStack() { return 0; }
 184 void SetTLSFakeStack(FakeStack *fs) { }
 185 #endif  // (SANITIZER_LINUX && !SANITIZER_ANDROID) || SANITIZER_FUCHSIA
 186
 187 static FakeStack *GetFakeStack() {
 188   AsanThread *t = GetCurrentThread();
 189   if (!t) return nullptr;
 190   return t->fake_stack();
 191 }
 192
 193 static FakeStack *GetFakeStackFast() {
 194   if (FakeStack *fs = GetTLSFakeStack())
 195     return fs;
 196   if (!__asan_option_detect_stack_use_after_return)
 197     return nullptr;
 198   return GetFakeStack();
 199 }
 200
 201 ALWAYS_INLINE uptr OnMalloc(uptr class_id, uptr size) {
 202   FakeStack *fs = GetFakeStackFast();
 203   if (!fs) return 0;
 204   uptr local_stack;
 205   uptr real_stack = reinterpret_cast<uptr>(&local_stack);
 206   FakeFrame *ff = fs->Allocate(fs->stack_size_log(), class_id, real_stack);
 207   if (!ff) return 0;  // Out of fake stack.
 208   uptr ptr = reinterpret_cast<uptr>(ff);
 209   SetShadow(ptr, size, class_id, 0);
 210   return ptr;
 211 }
 212
 213 ALWAYS_INLINE void OnFree(uptr ptr, uptr class_id, uptr size) {
 214   FakeStack::Deallocate(ptr, class_id);
 215   SetShadow(ptr, size, class_id, kMagic8);
 216 }
 217
 218 } // namespace __asan
 219
 220 // ---------------------- Interface ---------------- {{{1
 221 using namespace __asan;
 222 #define DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(class_id)                       \
 223   extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr                                \
 224       __asan_stack_malloc_##class_id(uptr size) {                              \
 225     return OnMalloc(class_id, size);                                           \
 226   }                                                                            \
 227   extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __asan_stack_free_##class_id(  \
 228       uptr ptr, uptr size) {                                                   \
 229     OnFree(ptr, class_id, size);                                               \
 230   }
 231
 232 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(0)
 233 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(1)
 234 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(2)
 235 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(3)
 236 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(4)
 237 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(5)
 238 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(6)
 239 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(7)
 240 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(8)
 241 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(9)
 242 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(10)
 243 extern "C" {
 244 SANITIZER_INTERFACE_ATTRIBUTE
 245 void *__asan_get_current_fake_stack() { return GetFakeStackFast(); }
 246
 247 SANITIZER_INTERFACE_ATTRIBUTE
 248 void *__asan_addr_is_in_fake_stack(void *fake_stack, void *addr, void **beg,
 249                                    void **end) {
 250   FakeStack *fs = reinterpret_cast<FakeStack*>(fake_stack);
 251   if (!fs) return nullptr;
 252   uptr frame_beg, frame_end;
 253   FakeFrame *frame = reinterpret_cast<FakeFrame *>(fs->AddrIsInFakeStack(
 254       reinterpret_cast<uptr>(addr), &frame_beg, &frame_end));
 255   if (!frame) return nullptr;
 256   if (frame->magic != kCurrentStackFrameMagic)
 257     return nullptr;
 258   if (beg) *beg = reinterpret_cast<void*>(frame_beg);
 259   if (end) *end = reinterpret_cast<void*>(frame_end);
 260   return reinterpret_cast<void*>(frame->real_stack);
 261 }
 262
 263 SANITIZER_INTERFACE_ATTRIBUTE
 264 void __asan_alloca_poison(uptr addr, uptr size) {
 265   uptr LeftRedzoneAddr = addr - kAllocaRedzoneSize;
 266   uptr PartialRzAddr = addr + size;
 267   uptr RightRzAddr = (PartialRzAddr + kAllocaRedzoneMask) & ~kAllocaRedzoneMask;
 268   uptr PartialRzAligned = PartialRzAddr & ~(SHADOW_GRANULARITY - 1);
 269   FastPoisonShadow(LeftRedzoneAddr, kAllocaRedzoneSize, kAsanAllocaLeftMagic);
 270   FastPoisonShadowPartialRightRedzone(
 271       PartialRzAligned, PartialRzAddr % SHADOW_GRANULARITY,
 272       RightRzAddr - PartialRzAligned, kAsanAllocaRightMagic);
 273   FastPoisonShadow(RightRzAddr, kAllocaRedzoneSize, kAsanAllocaRightMagic);
 274 }
 275
 276 SANITIZER_INTERFACE_ATTRIBUTE
 277 void __asan_allocas_unpoison(uptr top, uptr bottom) {
 278   if ((!top) || (top > bottom)) return;
 279   REAL(memset)(reinterpret_cast<void*>(MemToShadow(top)), 0,
 280                (bottom - top) / SHADOW_GRANULARITY);
 281 }
 282 } // extern "C"