1 //===--- PthreadLockChecker.cpp - Check for locking problems ---*- C++ -*--===//
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 defines PthreadLockChecker, a simple lock -> unlock checker.
11 // Also handles XNU locks, which behave similarly enough to share code.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "ClangSACheckers.h"
16 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
17 #include "clang/StaticAnalyzer/Core/Checker.h"
18 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
21 #include "llvm/ADT/ImmutableList.h"
22
23 using namespace clang;
24 using namespace ento;
25
26 namespace {
27
28 struct LockState {
29 enum Kind { Destroyed, Locked, Unlocked } K;
30
31 private:
LockState__anon923fbf950111::LockState32 LockState(Kind K) : K(K) {}
33
34 public:
getLocked__anon923fbf950111::LockState35 static LockState getLocked() { return LockState(Locked); }
getUnlocked__anon923fbf950111::LockState36 static LockState getUnlocked() { return LockState(Unlocked); }
getDestroyed__anon923fbf950111::LockState37 static LockState getDestroyed() { return LockState(Destroyed); }
38
operator ==__anon923fbf950111::LockState39 bool operator==(const LockState &X) const {
40 return K == X.K;
41 }
42
isLocked__anon923fbf950111::LockState43 bool isLocked() const { return K == Locked; }
isUnlocked__anon923fbf950111::LockState44 bool isUnlocked() const { return K == Unlocked; }
isDestroyed__anon923fbf950111::LockState45 bool isDestroyed() const { return K == Destroyed; }
46
Profile__anon923fbf950111::LockState47 void Profile(llvm::FoldingSetNodeID &ID) const {
48 ID.AddInteger(K);
49 }
50 };
51
52 class PthreadLockChecker : public Checker< check::PostStmt<CallExpr> > {
53 mutable std::unique_ptr<BugType> BT_doublelock;
54 mutable std::unique_ptr<BugType> BT_doubleunlock;
55 mutable std::unique_ptr<BugType> BT_destroylock;
56 mutable std::unique_ptr<BugType> BT_initlock;
57 mutable std::unique_ptr<BugType> BT_lor;
58 enum LockingSemantics {
59 NotApplicable = 0,
60 PthreadSemantics,
61 XNUSemantics
62 };
63 public:
64 void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
65
66 void AcquireLock(CheckerContext &C, const CallExpr *CE, SVal lock,
67 bool isTryLock, enum LockingSemantics semantics) const;
68
69 void ReleaseLock(CheckerContext &C, const CallExpr *CE, SVal lock) const;
70 void DestroyLock(CheckerContext &C, const CallExpr *CE, SVal Lock) const;
71 void InitLock(CheckerContext &C, const CallExpr *CE, SVal Lock) const;
72 void reportUseDestroyedBug(CheckerContext &C, const CallExpr *CE) const;
73 };
74 } // end anonymous namespace
75
76 // GDM Entry for tracking lock state.
REGISTER_LIST_WITH_PROGRAMSTATE(LockSet,const MemRegion *)77 REGISTER_LIST_WITH_PROGRAMSTATE(LockSet, const MemRegion *)
78
79 REGISTER_MAP_WITH_PROGRAMSTATE(LockMap, const MemRegion *, LockState)
80
81 void PthreadLockChecker::checkPostStmt(const CallExpr *CE,
82 CheckerContext &C) const {
83 ProgramStateRef state = C.getState();
84 const LocationContext *LCtx = C.getLocationContext();
85 StringRef FName = C.getCalleeName(CE);
86 if (FName.empty())
87 return;
88
89 if (CE->getNumArgs() != 1 && CE->getNumArgs() != 2)
90 return;
91
92 if (FName == "pthread_mutex_lock" ||
93 FName == "pthread_rwlock_rdlock" ||
94 FName == "pthread_rwlock_wrlock")
95 AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
96 false, PthreadSemantics);
97 else if (FName == "lck_mtx_lock" ||
98 FName == "lck_rw_lock_exclusive" ||
99 FName == "lck_rw_lock_shared")
100 AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
101 false, XNUSemantics);
102 else if (FName == "pthread_mutex_trylock" ||
103 FName == "pthread_rwlock_tryrdlock" ||
104 FName == "pthread_rwlock_trywrlock")
105 AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
106 true, PthreadSemantics);
107 else if (FName == "lck_mtx_try_lock" ||
108 FName == "lck_rw_try_lock_exclusive" ||
109 FName == "lck_rw_try_lock_shared")
110 AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
111 true, XNUSemantics);
112 else if (FName == "pthread_mutex_unlock" ||
113 FName == "pthread_rwlock_unlock" ||
114 FName == "lck_mtx_unlock" ||
115 FName == "lck_rw_done")
116 ReleaseLock(C, CE, state->getSVal(CE->getArg(0), LCtx));
117 else if (FName == "pthread_mutex_destroy" ||
118 FName == "lck_mtx_destroy")
119 DestroyLock(C, CE, state->getSVal(CE->getArg(0), LCtx));
120 else if (FName == "pthread_mutex_init")
121 InitLock(C, CE, state->getSVal(CE->getArg(0), LCtx));
122 }
123
AcquireLock(CheckerContext & C,const CallExpr * CE,SVal lock,bool isTryLock,enum LockingSemantics semantics) const124 void PthreadLockChecker::AcquireLock(CheckerContext &C, const CallExpr *CE,
125 SVal lock, bool isTryLock,
126 enum LockingSemantics semantics) const {
127
128 const MemRegion *lockR = lock.getAsRegion();
129 if (!lockR)
130 return;
131
132 ProgramStateRef state = C.getState();
133
134 SVal X = state->getSVal(CE, C.getLocationContext());
135 if (X.isUnknownOrUndef())
136 return;
137
138 DefinedSVal retVal = X.castAs<DefinedSVal>();
139
140 if (const LockState *LState = state->get<LockMap>(lockR)) {
141 if (LState->isLocked()) {
142 if (!BT_doublelock)
143 BT_doublelock.reset(new BugType(this, "Double locking",
144 "Lock checker"));
145 ExplodedNode *N = C.generateErrorNode();
146 if (!N)
147 return;
148 auto report = llvm::make_unique<BugReport>(
149 *BT_doublelock, "This lock has already been acquired", N);
150 report->addRange(CE->getArg(0)->getSourceRange());
151 C.emitReport(std::move(report));
152 return;
153 } else if (LState->isDestroyed()) {
154 reportUseDestroyedBug(C, CE);
155 return;
156 }
157 }
158
159 ProgramStateRef lockSucc = state;
160 if (isTryLock) {
161 // Bifurcate the state, and allow a mode where the lock acquisition fails.
162 ProgramStateRef lockFail;
163 switch (semantics) {
164 case PthreadSemantics:
165 std::tie(lockFail, lockSucc) = state->assume(retVal);
166 break;
167 case XNUSemantics:
168 std::tie(lockSucc, lockFail) = state->assume(retVal);
169 break;
170 default:
171 llvm_unreachable("Unknown tryLock locking semantics");
172 }
173 assert(lockFail && lockSucc);
174 C.addTransition(lockFail);
175
176 } else if (semantics == PthreadSemantics) {
177 // Assume that the return value was 0.
178 lockSucc = state->assume(retVal, false);
179 assert(lockSucc);
180
181 } else {
182 // XNU locking semantics return void on non-try locks
183 assert((semantics == XNUSemantics) && "Unknown locking semantics");
184 lockSucc = state;
185 }
186
187 // Record that the lock was acquired.
188 lockSucc = lockSucc->add<LockSet>(lockR);
189 lockSucc = lockSucc->set<LockMap>(lockR, LockState::getLocked());
190 C.addTransition(lockSucc);
191 }
192
ReleaseLock(CheckerContext & C,const CallExpr * CE,SVal lock) const193 void PthreadLockChecker::ReleaseLock(CheckerContext &C, const CallExpr *CE,
194 SVal lock) const {
195
196 const MemRegion *lockR = lock.getAsRegion();
197 if (!lockR)
198 return;
199
200 ProgramStateRef state = C.getState();
201
202 if (const LockState *LState = state->get<LockMap>(lockR)) {
203 if (LState->isUnlocked()) {
204 if (!BT_doubleunlock)
205 BT_doubleunlock.reset(new BugType(this, "Double unlocking",
206 "Lock checker"));
207 ExplodedNode *N = C.generateErrorNode();
208 if (!N)
209 return;
210 auto Report = llvm::make_unique<BugReport>(
211 *BT_doubleunlock, "This lock has already been unlocked", N);
212 Report->addRange(CE->getArg(0)->getSourceRange());
213 C.emitReport(std::move(Report));
214 return;
215 } else if (LState->isDestroyed()) {
216 reportUseDestroyedBug(C, CE);
217 return;
218 }
219 }
220
221 LockSetTy LS = state->get<LockSet>();
222
223 // FIXME: Better analysis requires IPA for wrappers.
224
225 if (!LS.isEmpty()) {
226 const MemRegion *firstLockR = LS.getHead();
227 if (firstLockR != lockR) {
228 if (!BT_lor)
229 BT_lor.reset(new BugType(this, "Lock order reversal", "Lock checker"));
230 ExplodedNode *N = C.generateErrorNode();
231 if (!N)
232 return;
233 auto report = llvm::make_unique<BugReport>(
234 *BT_lor, "This was not the most recently acquired lock. Possible "
235 "lock order reversal", N);
236 report->addRange(CE->getArg(0)->getSourceRange());
237 C.emitReport(std::move(report));
238 return;
239 }
240 // Record that the lock was released.
241 state = state->set<LockSet>(LS.getTail());
242 }
243
244 state = state->set<LockMap>(lockR, LockState::getUnlocked());
245 C.addTransition(state);
246 }
247
DestroyLock(CheckerContext & C,const CallExpr * CE,SVal Lock) const248 void PthreadLockChecker::DestroyLock(CheckerContext &C, const CallExpr *CE,
249 SVal Lock) const {
250
251 const MemRegion *LockR = Lock.getAsRegion();
252 if (!LockR)
253 return;
254
255 ProgramStateRef State = C.getState();
256
257 const LockState *LState = State->get<LockMap>(LockR);
258 if (!LState || LState->isUnlocked()) {
259 State = State->set<LockMap>(LockR, LockState::getDestroyed());
260 C.addTransition(State);
261 return;
262 }
263
264 StringRef Message;
265
266 if (LState->isLocked()) {
267 Message = "This lock is still locked";
268 } else {
269 Message = "This lock has already been destroyed";
270 }
271
272 if (!BT_destroylock)
273 BT_destroylock.reset(new BugType(this, "Destroy invalid lock",
274 "Lock checker"));
275 ExplodedNode *N = C.generateErrorNode();
276 if (!N)
277 return;
278 auto Report = llvm::make_unique<BugReport>(*BT_destroylock, Message, N);
279 Report->addRange(CE->getArg(0)->getSourceRange());
280 C.emitReport(std::move(Report));
281 }
282
InitLock(CheckerContext & C,const CallExpr * CE,SVal Lock) const283 void PthreadLockChecker::InitLock(CheckerContext &C, const CallExpr *CE,
284 SVal Lock) const {
285
286 const MemRegion *LockR = Lock.getAsRegion();
287 if (!LockR)
288 return;
289
290 ProgramStateRef State = C.getState();
291
292 const struct LockState *LState = State->get<LockMap>(LockR);
293 if (!LState || LState->isDestroyed()) {
294 State = State->set<LockMap>(LockR, LockState::getUnlocked());
295 C.addTransition(State);
296 return;
297 }
298
299 StringRef Message;
300
301 if (LState->isLocked()) {
302 Message = "This lock is still being held";
303 } else {
304 Message = "This lock has already been initialized";
305 }
306
307 if (!BT_initlock)
308 BT_initlock.reset(new BugType(this, "Init invalid lock",
309 "Lock checker"));
310 ExplodedNode *N = C.generateErrorNode();
311 if (!N)
312 return;
313 auto Report = llvm::make_unique<BugReport>(*BT_initlock, Message, N);
314 Report->addRange(CE->getArg(0)->getSourceRange());
315 C.emitReport(std::move(Report));
316 }
317
reportUseDestroyedBug(CheckerContext & C,const CallExpr * CE) const318 void PthreadLockChecker::reportUseDestroyedBug(CheckerContext &C,
319 const CallExpr *CE) const {
320 if (!BT_destroylock)
321 BT_destroylock.reset(new BugType(this, "Use destroyed lock",
322 "Lock checker"));
323 ExplodedNode *N = C.generateErrorNode();
324 if (!N)
325 return;
326 auto Report = llvm::make_unique<BugReport>(
327 *BT_destroylock, "This lock has already been destroyed", N);
328 Report->addRange(CE->getArg(0)->getSourceRange());
329 C.emitReport(std::move(Report));
330 }
331
registerPthreadLockChecker(CheckerManager & mgr)332 void ento::registerPthreadLockChecker(CheckerManager &mgr) {
333 mgr.registerChecker<PthreadLockChecker>();
334 }
335