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1 //===-- asan_fake_stack.cc ------------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file is a part of AddressSanitizer, an address sanity checker.
11 //
12 // FakeStack is used to detect use-after-return bugs.
13 //===----------------------------------------------------------------------===//
14 
15 #include "asan_allocator.h"
16 #include "asan_poisoning.h"
17 #include "asan_thread.h"
18 
19 namespace __asan {
20 
21 static const u64 kMagic1 = kAsanStackAfterReturnMagic;
22 static const u64 kMagic2 = (kMagic1 << 8) | kMagic1;
23 static const u64 kMagic4 = (kMagic2 << 16) | kMagic2;
24 static const u64 kMagic8 = (kMagic4 << 32) | kMagic4;
25 
26 static const u64 kAllocaRedzoneSize = 32UL;
27 static const u64 kAllocaRedzoneMask = 31UL;
28 
29 // For small size classes inline PoisonShadow for better performance.
SetShadow(uptr ptr,uptr size,uptr class_id,u64 magic)30 ALWAYS_INLINE void SetShadow(uptr ptr, uptr size, uptr class_id, u64 magic) {
31   CHECK_EQ(SHADOW_SCALE, 3);  // This code expects SHADOW_SCALE=3.
32   u64 *shadow = reinterpret_cast<u64*>(MemToShadow(ptr));
33   if (class_id <= 6) {
34     for (uptr i = 0; i < (((uptr)1) << class_id); i++) {
35       shadow[i] = magic;
36       // Make sure this does not become memset.
37       SanitizerBreakOptimization(nullptr);
38     }
39   } else {
40     // The size class is too big, it's cheaper to poison only size bytes.
41     PoisonShadow(ptr, size, static_cast<u8>(magic));
42   }
43 }
44 
Create(uptr stack_size_log)45 FakeStack *FakeStack::Create(uptr stack_size_log) {
46   static uptr kMinStackSizeLog = 16;
47   static uptr kMaxStackSizeLog = FIRST_32_SECOND_64(24, 28);
48   if (stack_size_log < kMinStackSizeLog)
49     stack_size_log = kMinStackSizeLog;
50   if (stack_size_log > kMaxStackSizeLog)
51     stack_size_log = kMaxStackSizeLog;
52   uptr size = RequiredSize(stack_size_log);
53   FakeStack *res = reinterpret_cast<FakeStack *>(
54       flags()->uar_noreserve ? MmapNoReserveOrDie(size, "FakeStack")
55                              : MmapOrDie(size, "FakeStack"));
56   res->stack_size_log_ = stack_size_log;
57   u8 *p = reinterpret_cast<u8 *>(res);
58   VReport(1, "T%d: FakeStack created: %p -- %p stack_size_log: %zd; "
59           "mmapped %zdK, noreserve=%d \n",
60           GetCurrentTidOrInvalid(), p,
61           p + FakeStack::RequiredSize(stack_size_log), stack_size_log,
62           size >> 10, flags()->uar_noreserve);
63   return res;
64 }
65 
Destroy(int tid)66 void FakeStack::Destroy(int tid) {
67   PoisonAll(0);
68   if (Verbosity() >= 2) {
69     InternalScopedString str(kNumberOfSizeClasses * 50);
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 
PoisonAll(u8 magic)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
Allocate(uptr stack_size_log,uptr class_id,uptr real_stack)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-atimic 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 
AddrIsInFakeStack(uptr ptr,uptr * frame_beg,uptr * frame_end)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 
HandleNoReturn()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.
GC(uptr real_stack)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 
ForEachFakeFrame(RangeIteratorCallback callback,void * arg)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
175 static THREADLOCAL FakeStack *fake_stack_tls;
176 
GetTLSFakeStack()177 FakeStack *GetTLSFakeStack() {
178   return fake_stack_tls;
179 }
SetTLSFakeStack(FakeStack * fs)180 void SetTLSFakeStack(FakeStack *fs) {
181   fake_stack_tls = fs;
182 }
183 #else
GetTLSFakeStack()184 FakeStack *GetTLSFakeStack() { return 0; }
SetTLSFakeStack(FakeStack * fs)185 void SetTLSFakeStack(FakeStack *fs) { }
186 #endif  // SANITIZER_LINUX && !SANITIZER_ANDROID
187 
GetFakeStack()188 static FakeStack *GetFakeStack() {
189   AsanThread *t = GetCurrentThread();
190   if (!t) return nullptr;
191   return t->fake_stack();
192 }
193 
GetFakeStackFast()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 
OnMalloc(uptr class_id,uptr size)202 ALWAYS_INLINE uptr OnMalloc(uptr class_id, uptr size) {
203   FakeStack *fs = GetFakeStackFast();
204   if (!fs) return 0;
205   uptr local_stack;
206   uptr real_stack = reinterpret_cast<uptr>(&local_stack);
207   FakeFrame *ff = fs->Allocate(fs->stack_size_log(), class_id, real_stack);
208   if (!ff) return 0;  // Out of fake stack.
209   uptr ptr = reinterpret_cast<uptr>(ff);
210   SetShadow(ptr, size, class_id, 0);
211   return ptr;
212 }
213 
OnFree(uptr ptr,uptr class_id,uptr size)214 ALWAYS_INLINE void OnFree(uptr ptr, uptr class_id, uptr size) {
215   FakeStack::Deallocate(ptr, class_id);
216   SetShadow(ptr, size, class_id, kMagic8);
217 }
218 
219 } // namespace __asan
220 
221 // ---------------------- Interface ---------------- {{{1
222 using namespace __asan;
223 #define DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(class_id)                       \
224   extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr                                \
225       __asan_stack_malloc_##class_id(uptr size) {                              \
226     return OnMalloc(class_id, size);                                           \
227   }                                                                            \
228   extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __asan_stack_free_##class_id(  \
229       uptr ptr, uptr size) {                                                   \
230     OnFree(ptr, class_id, size);                                               \
231   }
232 
233 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(0)
234 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(1)
235 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(2)
236 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(3)
237 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(4)
238 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(5)
239 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(6)
240 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(7)
241 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(8)
242 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(9)
243 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(10)
244 extern "C" {
245 SANITIZER_INTERFACE_ATTRIBUTE
__asan_get_current_fake_stack()246 void *__asan_get_current_fake_stack() { return GetFakeStackFast(); }
247 
248 SANITIZER_INTERFACE_ATTRIBUTE
__asan_addr_is_in_fake_stack(void * fake_stack,void * addr,void ** beg,void ** end)249 void *__asan_addr_is_in_fake_stack(void *fake_stack, void *addr, void **beg,
250                                    void **end) {
251   FakeStack *fs = reinterpret_cast<FakeStack*>(fake_stack);
252   if (!fs) return nullptr;
253   uptr frame_beg, frame_end;
254   FakeFrame *frame = reinterpret_cast<FakeFrame *>(fs->AddrIsInFakeStack(
255       reinterpret_cast<uptr>(addr), &frame_beg, &frame_end));
256   if (!frame) return nullptr;
257   if (frame->magic != kCurrentStackFrameMagic)
258     return nullptr;
259   if (beg) *beg = reinterpret_cast<void*>(frame_beg);
260   if (end) *end = reinterpret_cast<void*>(frame_end);
261   return reinterpret_cast<void*>(frame->real_stack);
262 }
263 
264 SANITIZER_INTERFACE_ATTRIBUTE
__asan_alloca_poison(uptr addr,uptr size)265 void __asan_alloca_poison(uptr addr, uptr size) {
266   uptr LeftRedzoneAddr = addr - kAllocaRedzoneSize;
267   uptr PartialRzAddr = addr + size;
268   uptr RightRzAddr = (PartialRzAddr + kAllocaRedzoneMask) & ~kAllocaRedzoneMask;
269   uptr PartialRzAligned = PartialRzAddr & ~(SHADOW_GRANULARITY - 1);
270   FastPoisonShadow(LeftRedzoneAddr, kAllocaRedzoneSize, kAsanAllocaLeftMagic);
271   FastPoisonShadowPartialRightRedzone(
272       PartialRzAligned, PartialRzAddr % SHADOW_GRANULARITY,
273       RightRzAddr - PartialRzAligned, kAsanAllocaRightMagic);
274   FastPoisonShadow(RightRzAddr, kAllocaRedzoneSize, kAsanAllocaRightMagic);
275 }
276 
277 SANITIZER_INTERFACE_ATTRIBUTE
__asan_allocas_unpoison(uptr top,uptr bottom)278 void __asan_allocas_unpoison(uptr top, uptr bottom) {
279   if ((!top) || (top > bottom)) return;
280   REAL(memset)(reinterpret_cast<void*>(MemToShadow(top)), 0,
281                (bottom - top) / SHADOW_GRANULARITY);
282 }
283 } // extern "C"
284