MallocChecker.cpp revision fe571608b925079227d053a459eca86f7408e5c6
1//=== MallocChecker.cpp - A malloc/free checker -------------------*- 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 file defines malloc/free checker, which checks for potential memory 11// leaks, double free, and use-after-free problems. 12// 13//===----------------------------------------------------------------------===// 14 15#include "ClangSACheckers.h" 16#include "clang/StaticAnalyzer/Core/Checker.h" 17#include "clang/StaticAnalyzer/Core/CheckerManager.h" 18#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 19#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 20#include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.h" 21#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" 22#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h" 23#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h" 24#include "clang/Basic/SourceManager.h" 25#include "llvm/ADT/ImmutableMap.h" 26#include "llvm/ADT/SmallString.h" 27#include "llvm/ADT/STLExtras.h" 28using namespace clang; 29using namespace ento; 30 31namespace { 32 33class RefState { 34 enum Kind { AllocateUnchecked, AllocateFailed, Released, Escaped, 35 Relinquished } K; 36 const Stmt *S; 37 38public: 39 RefState(Kind k, const Stmt *s) : K(k), S(s) {} 40 41 bool isAllocated() const { return K == AllocateUnchecked; } 42 //bool isFailed() const { return K == AllocateFailed; } 43 bool isReleased() const { return K == Released; } 44 //bool isEscaped() const { return K == Escaped; } 45 //bool isRelinquished() const { return K == Relinquished; } 46 const Stmt *getStmt() const { return S; } 47 48 bool operator==(const RefState &X) const { 49 return K == X.K && S == X.S; 50 } 51 52 static RefState getAllocateUnchecked(const Stmt *s) { 53 return RefState(AllocateUnchecked, s); 54 } 55 static RefState getAllocateFailed() { 56 return RefState(AllocateFailed, 0); 57 } 58 static RefState getReleased(const Stmt *s) { return RefState(Released, s); } 59 static RefState getEscaped(const Stmt *s) { return RefState(Escaped, s); } 60 static RefState getRelinquished(const Stmt *s) { 61 return RefState(Relinquished, s); 62 } 63 64 void Profile(llvm::FoldingSetNodeID &ID) const { 65 ID.AddInteger(K); 66 ID.AddPointer(S); 67 } 68}; 69 70struct ReallocPair { 71 SymbolRef ReallocatedSym; 72 bool IsFreeOnFailure; 73 ReallocPair(SymbolRef S, bool F) : ReallocatedSym(S), IsFreeOnFailure(F) {} 74 void Profile(llvm::FoldingSetNodeID &ID) const { 75 ID.AddInteger(IsFreeOnFailure); 76 ID.AddPointer(ReallocatedSym); 77 } 78 bool operator==(const ReallocPair &X) const { 79 return ReallocatedSym == X.ReallocatedSym && 80 IsFreeOnFailure == X.IsFreeOnFailure; 81 } 82}; 83 84class MallocChecker : public Checker<check::DeadSymbols, 85 check::EndPath, 86 check::PreStmt<ReturnStmt>, 87 check::PreStmt<CallExpr>, 88 check::PostStmt<CallExpr>, 89 check::Location, 90 check::Bind, 91 eval::Assume, 92 check::RegionChanges> 93{ 94 mutable OwningPtr<BuiltinBug> BT_DoubleFree; 95 mutable OwningPtr<BuiltinBug> BT_Leak; 96 mutable OwningPtr<BuiltinBug> BT_UseFree; 97 mutable OwningPtr<BuiltinBug> BT_UseRelinquished; 98 mutable OwningPtr<BuiltinBug> BT_BadFree; 99 mutable IdentifierInfo *II_malloc, *II_free, *II_realloc, *II_calloc, 100 *II_valloc, *II_reallocf; 101 102public: 103 MallocChecker() : II_malloc(0), II_free(0), II_realloc(0), II_calloc(0), 104 II_valloc(0), II_reallocf(0) {} 105 106 /// In pessimistic mode, the checker assumes that it does not know which 107 /// functions might free the memory. 108 struct ChecksFilter { 109 DefaultBool CMallocPessimistic; 110 DefaultBool CMallocOptimistic; 111 }; 112 113 ChecksFilter Filter; 114 115 void checkPreStmt(const CallExpr *S, CheckerContext &C) const; 116 void checkPostStmt(const CallExpr *CE, CheckerContext &C) const; 117 void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const; 118 void checkEndPath(CheckerContext &C) const; 119 void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const; 120 ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond, 121 bool Assumption) const; 122 void checkLocation(SVal l, bool isLoad, const Stmt *S, 123 CheckerContext &C) const; 124 void checkBind(SVal location, SVal val, const Stmt*S, 125 CheckerContext &C) const; 126 ProgramStateRef 127 checkRegionChanges(ProgramStateRef state, 128 const StoreManager::InvalidatedSymbols *invalidated, 129 ArrayRef<const MemRegion *> ExplicitRegions, 130 ArrayRef<const MemRegion *> Regions, 131 const CallOrObjCMessage *Call) const; 132 bool wantsRegionChangeUpdate(ProgramStateRef state) const { 133 return true; 134 } 135 136private: 137 void initIdentifierInfo(ASTContext &C) const; 138 139 /// Check if this is one of the functions which can allocate/reallocate memory 140 /// pointed to by one of its arguments. 141 bool isMemFunction(const FunctionDecl *FD, ASTContext &C) const; 142 143 static void MallocMem(CheckerContext &C, const CallExpr *CE); 144 static void MallocMemReturnsAttr(CheckerContext &C, const CallExpr *CE, 145 const OwnershipAttr* Att); 146 static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE, 147 const Expr *SizeEx, SVal Init, 148 ProgramStateRef state) { 149 return MallocMemAux(C, CE, 150 state->getSVal(SizeEx, C.getLocationContext()), 151 Init, state); 152 } 153 static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE, 154 SVal SizeEx, SVal Init, 155 ProgramStateRef state); 156 157 void FreeMem(CheckerContext &C, const CallExpr *CE) const; 158 void FreeMemAttr(CheckerContext &C, const CallExpr *CE, 159 const OwnershipAttr* Att) const; 160 ProgramStateRef FreeMemAux(CheckerContext &C, const CallExpr *CE, 161 ProgramStateRef state, unsigned Num, 162 bool Hold) const; 163 164 void ReallocMem(CheckerContext &C, const CallExpr *CE, 165 bool FreesMemOnFailure) const; 166 static void CallocMem(CheckerContext &C, const CallExpr *CE); 167 168 bool checkEscape(SymbolRef Sym, const Stmt *S, CheckerContext &C) const; 169 bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C, 170 const Stmt *S = 0) const; 171 172 /// Check if the function is not known to us. So, for example, we could 173 /// conservatively assume it can free/reallocate it's pointer arguments. 174 bool hasUnknownBehavior(const FunctionDecl *FD, ProgramStateRef State) const; 175 176 static bool SummarizeValue(raw_ostream &os, SVal V); 177 static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR); 178 void ReportBadFree(CheckerContext &C, SVal ArgVal, SourceRange range) const; 179 180 void reportLeak(SymbolRef Sym, ExplodedNode *N, CheckerContext &C) const; 181 182 /// The bug visitor which allows us to print extra diagnostics along the 183 /// BugReport path. For example, showing the allocation site of the leaked 184 /// region. 185 class MallocBugVisitor : public BugReporterVisitor { 186 protected: 187 enum NotificationMode { 188 Normal, 189 Complete, 190 ReallocationFailed 191 }; 192 193 // The allocated region symbol tracked by the main analysis. 194 SymbolRef Sym; 195 NotificationMode Mode; 196 197 public: 198 MallocBugVisitor(SymbolRef S) : Sym(S), Mode(Normal) {} 199 virtual ~MallocBugVisitor() {} 200 201 void Profile(llvm::FoldingSetNodeID &ID) const { 202 static int X = 0; 203 ID.AddPointer(&X); 204 ID.AddPointer(Sym); 205 } 206 207 inline bool isAllocated(const RefState *S, const RefState *SPrev, 208 const Stmt *Stmt) { 209 // Did not track -> allocated. Other state (released) -> allocated. 210 return (Stmt && isa<CallExpr>(Stmt) && 211 (S && S->isAllocated()) && (!SPrev || !SPrev->isAllocated())); 212 } 213 214 inline bool isReleased(const RefState *S, const RefState *SPrev, 215 const Stmt *Stmt) { 216 // Did not track -> released. Other state (allocated) -> released. 217 return (Stmt && isa<CallExpr>(Stmt) && 218 (S && S->isReleased()) && (!SPrev || !SPrev->isReleased())); 219 } 220 221 inline bool isReallocFailedCheck(const RefState *S, const RefState *SPrev, 222 const Stmt *Stmt) { 223 // If the expression is not a call, and the state change is 224 // released -> allocated, it must be the realloc return value 225 // check. If we have to handle more cases here, it might be cleaner just 226 // to track this extra bit in the state itself. 227 return ((!Stmt || !isa<CallExpr>(Stmt)) && 228 (S && S->isAllocated()) && (SPrev && !SPrev->isAllocated())); 229 } 230 231 PathDiagnosticPiece *VisitNode(const ExplodedNode *N, 232 const ExplodedNode *PrevN, 233 BugReporterContext &BRC, 234 BugReport &BR); 235 }; 236}; 237} // end anonymous namespace 238 239typedef llvm::ImmutableMap<SymbolRef, RefState> RegionStateTy; 240typedef llvm::ImmutableMap<SymbolRef, ReallocPair > ReallocMap; 241class RegionState {}; 242class ReallocPairs {}; 243namespace clang { 244namespace ento { 245 template <> 246 struct ProgramStateTrait<RegionState> 247 : public ProgramStatePartialTrait<RegionStateTy> { 248 static void *GDMIndex() { static int x; return &x; } 249 }; 250 251 template <> 252 struct ProgramStateTrait<ReallocPairs> 253 : public ProgramStatePartialTrait<ReallocMap> { 254 static void *GDMIndex() { static int x; return &x; } 255 }; 256} 257} 258 259namespace { 260class StopTrackingCallback : public SymbolVisitor { 261 ProgramStateRef state; 262public: 263 StopTrackingCallback(ProgramStateRef st) : state(st) {} 264 ProgramStateRef getState() const { return state; } 265 266 bool VisitSymbol(SymbolRef sym) { 267 state = state->remove<RegionState>(sym); 268 return true; 269 } 270}; 271} // end anonymous namespace 272 273void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const { 274 if (!II_malloc) 275 II_malloc = &Ctx.Idents.get("malloc"); 276 if (!II_free) 277 II_free = &Ctx.Idents.get("free"); 278 if (!II_realloc) 279 II_realloc = &Ctx.Idents.get("realloc"); 280 if (!II_reallocf) 281 II_reallocf = &Ctx.Idents.get("reallocf"); 282 if (!II_calloc) 283 II_calloc = &Ctx.Idents.get("calloc"); 284 if (!II_valloc) 285 II_valloc = &Ctx.Idents.get("valloc"); 286} 287 288bool MallocChecker::isMemFunction(const FunctionDecl *FD, ASTContext &C) const { 289 if (!FD) 290 return false; 291 IdentifierInfo *FunI = FD->getIdentifier(); 292 if (!FunI) 293 return false; 294 295 initIdentifierInfo(C); 296 297 // TODO: Add more here : ex: reallocf! 298 if (FunI == II_malloc || FunI == II_free || FunI == II_realloc || 299 FunI == II_reallocf || FunI == II_calloc || FunI == II_valloc) 300 return true; 301 302 if (Filter.CMallocOptimistic && FD->hasAttrs() && 303 FD->specific_attr_begin<OwnershipAttr>() != 304 FD->specific_attr_end<OwnershipAttr>()) 305 return true; 306 307 308 return false; 309} 310 311void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const { 312 const FunctionDecl *FD = C.getCalleeDecl(CE); 313 if (!FD) 314 return; 315 316 initIdentifierInfo(C.getASTContext()); 317 IdentifierInfo *FunI = FD->getIdentifier(); 318 if (!FunI) 319 return; 320 321 if (FunI == II_malloc || FunI == II_valloc) { 322 MallocMem(C, CE); 323 return; 324 } else if (FunI == II_realloc) { 325 ReallocMem(C, CE, false); 326 return; 327 } else if (FunI == II_reallocf) { 328 ReallocMem(C, CE, true); 329 return; 330 } else if (FunI == II_calloc) { 331 CallocMem(C, CE); 332 return; 333 }else if (FunI == II_free) { 334 FreeMem(C, CE); 335 return; 336 } 337 338 if (Filter.CMallocOptimistic) 339 // Check all the attributes, if there are any. 340 // There can be multiple of these attributes. 341 if (FD->hasAttrs()) { 342 for (specific_attr_iterator<OwnershipAttr> 343 i = FD->specific_attr_begin<OwnershipAttr>(), 344 e = FD->specific_attr_end<OwnershipAttr>(); 345 i != e; ++i) { 346 switch ((*i)->getOwnKind()) { 347 case OwnershipAttr::Returns: { 348 MallocMemReturnsAttr(C, CE, *i); 349 return; 350 } 351 case OwnershipAttr::Takes: 352 case OwnershipAttr::Holds: { 353 FreeMemAttr(C, CE, *i); 354 return; 355 } 356 } 357 } 358 } 359} 360 361void MallocChecker::MallocMem(CheckerContext &C, const CallExpr *CE) { 362 ProgramStateRef state = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), 363 C.getState()); 364 C.addTransition(state); 365} 366 367void MallocChecker::MallocMemReturnsAttr(CheckerContext &C, const CallExpr *CE, 368 const OwnershipAttr* Att) { 369 if (Att->getModule() != "malloc") 370 return; 371 372 OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end(); 373 if (I != E) { 374 ProgramStateRef state = 375 MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState()); 376 C.addTransition(state); 377 return; 378 } 379 ProgramStateRef state = MallocMemAux(C, CE, UnknownVal(), UndefinedVal(), 380 C.getState()); 381 C.addTransition(state); 382} 383 384ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C, 385 const CallExpr *CE, 386 SVal Size, SVal Init, 387 ProgramStateRef state) { 388 SValBuilder &svalBuilder = C.getSValBuilder(); 389 390 // Get the return value. 391 SVal retVal = state->getSVal(CE, C.getLocationContext()); 392 393 // We expect the malloc functions to return a pointer. 394 if (!isa<Loc>(retVal)) 395 return 0; 396 397 // Fill the region with the initialization value. 398 state = state->bindDefault(retVal, Init); 399 400 // Set the region's extent equal to the Size parameter. 401 const SymbolicRegion *R = 402 dyn_cast_or_null<SymbolicRegion>(retVal.getAsRegion()); 403 if (!R || !isa<DefinedOrUnknownSVal>(Size)) 404 return 0; 405 406 DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder); 407 DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size); 408 DefinedOrUnknownSVal extentMatchesSize = 409 svalBuilder.evalEQ(state, Extent, DefinedSize); 410 411 state = state->assume(extentMatchesSize, true); 412 assert(state); 413 414 SymbolRef Sym = retVal.getAsLocSymbol(); 415 assert(Sym); 416 417 // Set the symbol's state to Allocated. 418 return state->set<RegionState>(Sym, RefState::getAllocateUnchecked(CE)); 419} 420 421void MallocChecker::FreeMem(CheckerContext &C, const CallExpr *CE) const { 422 ProgramStateRef state = FreeMemAux(C, CE, C.getState(), 0, false); 423 424 if (state) 425 C.addTransition(state); 426} 427 428void MallocChecker::FreeMemAttr(CheckerContext &C, const CallExpr *CE, 429 const OwnershipAttr* Att) const { 430 if (Att->getModule() != "malloc") 431 return; 432 433 for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end(); 434 I != E; ++I) { 435 ProgramStateRef state = 436 FreeMemAux(C, CE, C.getState(), *I, 437 Att->getOwnKind() == OwnershipAttr::Holds); 438 if (state) 439 C.addTransition(state); 440 } 441} 442 443ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C, 444 const CallExpr *CE, 445 ProgramStateRef state, 446 unsigned Num, 447 bool Hold) const { 448 const Expr *ArgExpr = CE->getArg(Num); 449 SVal ArgVal = state->getSVal(ArgExpr, C.getLocationContext()); 450 if (!isa<DefinedOrUnknownSVal>(ArgVal)) 451 return 0; 452 DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal); 453 454 // Check for null dereferences. 455 if (!isa<Loc>(location)) 456 return 0; 457 458 // The explicit NULL case, no operation is performed. 459 ProgramStateRef notNullState, nullState; 460 llvm::tie(notNullState, nullState) = state->assume(location); 461 if (nullState && !notNullState) 462 return 0; 463 464 // Unknown values could easily be okay 465 // Undefined values are handled elsewhere 466 if (ArgVal.isUnknownOrUndef()) 467 return 0; 468 469 const MemRegion *R = ArgVal.getAsRegion(); 470 471 // Nonlocs can't be freed, of course. 472 // Non-region locations (labels and fixed addresses) also shouldn't be freed. 473 if (!R) { 474 ReportBadFree(C, ArgVal, ArgExpr->getSourceRange()); 475 return 0; 476 } 477 478 R = R->StripCasts(); 479 480 // Blocks might show up as heap data, but should not be free()d 481 if (isa<BlockDataRegion>(R)) { 482 ReportBadFree(C, ArgVal, ArgExpr->getSourceRange()); 483 return 0; 484 } 485 486 const MemSpaceRegion *MS = R->getMemorySpace(); 487 488 // Parameters, locals, statics, and globals shouldn't be freed. 489 if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) { 490 // FIXME: at the time this code was written, malloc() regions were 491 // represented by conjured symbols, which are all in UnknownSpaceRegion. 492 // This means that there isn't actually anything from HeapSpaceRegion 493 // that should be freed, even though we allow it here. 494 // Of course, free() can work on memory allocated outside the current 495 // function, so UnknownSpaceRegion is always a possibility. 496 // False negatives are better than false positives. 497 498 ReportBadFree(C, ArgVal, ArgExpr->getSourceRange()); 499 return 0; 500 } 501 502 const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R); 503 // Various cases could lead to non-symbol values here. 504 // For now, ignore them. 505 if (!SR) 506 return 0; 507 508 SymbolRef Sym = SR->getSymbol(); 509 const RefState *RS = state->get<RegionState>(Sym); 510 511 // If the symbol has not been tracked, return. This is possible when free() is 512 // called on a pointer that does not get its pointee directly from malloc(). 513 // Full support of this requires inter-procedural analysis. 514 if (!RS) 515 return 0; 516 517 // Check double free. 518 if (RS->isReleased()) { 519 if (ExplodedNode *N = C.generateSink()) { 520 if (!BT_DoubleFree) 521 BT_DoubleFree.reset( 522 new BuiltinBug("Double free", 523 "Try to free a memory block that has been released")); 524 BugReport *R = new BugReport(*BT_DoubleFree, 525 BT_DoubleFree->getDescription(), N); 526 R->addRange(ArgExpr->getSourceRange()); 527 R->addVisitor(new MallocBugVisitor(Sym)); 528 C.EmitReport(R); 529 } 530 return 0; 531 } 532 533 // Normal free. 534 if (Hold) 535 return state->set<RegionState>(Sym, RefState::getRelinquished(CE)); 536 return state->set<RegionState>(Sym, RefState::getReleased(CE)); 537} 538 539bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) { 540 if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V)) 541 os << "an integer (" << IntVal->getValue() << ")"; 542 else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V)) 543 os << "a constant address (" << ConstAddr->getValue() << ")"; 544 else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V)) 545 os << "the address of the label '" << Label->getLabel()->getName() << "'"; 546 else 547 return false; 548 549 return true; 550} 551 552bool MallocChecker::SummarizeRegion(raw_ostream &os, 553 const MemRegion *MR) { 554 switch (MR->getKind()) { 555 case MemRegion::FunctionTextRegionKind: { 556 const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl(); 557 if (FD) 558 os << "the address of the function '" << *FD << '\''; 559 else 560 os << "the address of a function"; 561 return true; 562 } 563 case MemRegion::BlockTextRegionKind: 564 os << "block text"; 565 return true; 566 case MemRegion::BlockDataRegionKind: 567 // FIXME: where the block came from? 568 os << "a block"; 569 return true; 570 default: { 571 const MemSpaceRegion *MS = MR->getMemorySpace(); 572 573 if (isa<StackLocalsSpaceRegion>(MS)) { 574 const VarRegion *VR = dyn_cast<VarRegion>(MR); 575 const VarDecl *VD; 576 if (VR) 577 VD = VR->getDecl(); 578 else 579 VD = NULL; 580 581 if (VD) 582 os << "the address of the local variable '" << VD->getName() << "'"; 583 else 584 os << "the address of a local stack variable"; 585 return true; 586 } 587 588 if (isa<StackArgumentsSpaceRegion>(MS)) { 589 const VarRegion *VR = dyn_cast<VarRegion>(MR); 590 const VarDecl *VD; 591 if (VR) 592 VD = VR->getDecl(); 593 else 594 VD = NULL; 595 596 if (VD) 597 os << "the address of the parameter '" << VD->getName() << "'"; 598 else 599 os << "the address of a parameter"; 600 return true; 601 } 602 603 if (isa<GlobalsSpaceRegion>(MS)) { 604 const VarRegion *VR = dyn_cast<VarRegion>(MR); 605 const VarDecl *VD; 606 if (VR) 607 VD = VR->getDecl(); 608 else 609 VD = NULL; 610 611 if (VD) { 612 if (VD->isStaticLocal()) 613 os << "the address of the static variable '" << VD->getName() << "'"; 614 else 615 os << "the address of the global variable '" << VD->getName() << "'"; 616 } else 617 os << "the address of a global variable"; 618 return true; 619 } 620 621 return false; 622 } 623 } 624} 625 626void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal, 627 SourceRange range) const { 628 if (ExplodedNode *N = C.generateSink()) { 629 if (!BT_BadFree) 630 BT_BadFree.reset(new BuiltinBug("Bad free")); 631 632 SmallString<100> buf; 633 llvm::raw_svector_ostream os(buf); 634 635 const MemRegion *MR = ArgVal.getAsRegion(); 636 if (MR) { 637 while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR)) 638 MR = ER->getSuperRegion(); 639 640 // Special case for alloca() 641 if (isa<AllocaRegion>(MR)) 642 os << "Argument to free() was allocated by alloca(), not malloc()"; 643 else { 644 os << "Argument to free() is "; 645 if (SummarizeRegion(os, MR)) 646 os << ", which is not memory allocated by malloc()"; 647 else 648 os << "not memory allocated by malloc()"; 649 } 650 } else { 651 os << "Argument to free() is "; 652 if (SummarizeValue(os, ArgVal)) 653 os << ", which is not memory allocated by malloc()"; 654 else 655 os << "not memory allocated by malloc()"; 656 } 657 658 BugReport *R = new BugReport(*BT_BadFree, os.str(), N); 659 R->addRange(range); 660 C.EmitReport(R); 661 } 662} 663 664void MallocChecker::ReallocMem(CheckerContext &C, const CallExpr *CE, 665 bool FreesOnFail) const { 666 ProgramStateRef state = C.getState(); 667 const Expr *arg0Expr = CE->getArg(0); 668 const LocationContext *LCtx = C.getLocationContext(); 669 SVal Arg0Val = state->getSVal(arg0Expr, LCtx); 670 if (!isa<DefinedOrUnknownSVal>(Arg0Val)) 671 return; 672 DefinedOrUnknownSVal arg0Val = cast<DefinedOrUnknownSVal>(Arg0Val); 673 674 SValBuilder &svalBuilder = C.getSValBuilder(); 675 676 DefinedOrUnknownSVal PtrEQ = 677 svalBuilder.evalEQ(state, arg0Val, svalBuilder.makeNull()); 678 679 // Get the size argument. If there is no size arg then give up. 680 const Expr *Arg1 = CE->getArg(1); 681 if (!Arg1) 682 return; 683 684 // Get the value of the size argument. 685 SVal Arg1ValG = state->getSVal(Arg1, LCtx); 686 if (!isa<DefinedOrUnknownSVal>(Arg1ValG)) 687 return; 688 DefinedOrUnknownSVal Arg1Val = cast<DefinedOrUnknownSVal>(Arg1ValG); 689 690 // Compare the size argument to 0. 691 DefinedOrUnknownSVal SizeZero = 692 svalBuilder.evalEQ(state, Arg1Val, 693 svalBuilder.makeIntValWithPtrWidth(0, false)); 694 695 ProgramStateRef StatePtrIsNull, StatePtrNotNull; 696 llvm::tie(StatePtrIsNull, StatePtrNotNull) = state->assume(PtrEQ); 697 ProgramStateRef StateSizeIsZero, StateSizeNotZero; 698 llvm::tie(StateSizeIsZero, StateSizeNotZero) = state->assume(SizeZero); 699 // We only assume exceptional states if they are definitely true; if the 700 // state is under-constrained, assume regular realloc behavior. 701 bool PrtIsNull = StatePtrIsNull && !StatePtrNotNull; 702 bool SizeIsZero = StateSizeIsZero && !StateSizeNotZero; 703 704 // If the ptr is NULL and the size is not 0, the call is equivalent to 705 // malloc(size). 706 if ( PrtIsNull && !SizeIsZero) { 707 ProgramStateRef stateMalloc = MallocMemAux(C, CE, CE->getArg(1), 708 UndefinedVal(), StatePtrIsNull); 709 C.addTransition(stateMalloc); 710 return; 711 } 712 713 if (PrtIsNull && SizeIsZero) 714 return; 715 716 // Get the from and to pointer symbols as in toPtr = realloc(fromPtr, size). 717 assert(!PrtIsNull); 718 SymbolRef FromPtr = arg0Val.getAsSymbol(); 719 SVal RetVal = state->getSVal(CE, LCtx); 720 SymbolRef ToPtr = RetVal.getAsSymbol(); 721 if (!FromPtr || !ToPtr) 722 return; 723 724 // If the size is 0, free the memory. 725 if (SizeIsZero) 726 if (ProgramStateRef stateFree = FreeMemAux(C, CE, StateSizeIsZero,0,false)){ 727 // The semantics of the return value are: 728 // If size was equal to 0, either NULL or a pointer suitable to be passed 729 // to free() is returned. 730 stateFree = stateFree->set<ReallocPairs>(ToPtr, 731 ReallocPair(FromPtr, FreesOnFail)); 732 C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr); 733 C.addTransition(stateFree); 734 return; 735 } 736 737 // Default behavior. 738 if (ProgramStateRef stateFree = FreeMemAux(C, CE, state, 0, false)) { 739 // FIXME: We should copy the content of the original buffer. 740 ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1), 741 UnknownVal(), stateFree); 742 if (!stateRealloc) 743 return; 744 stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr, 745 ReallocPair(FromPtr, FreesOnFail)); 746 C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr); 747 C.addTransition(stateRealloc); 748 return; 749 } 750} 751 752void MallocChecker::CallocMem(CheckerContext &C, const CallExpr *CE) { 753 ProgramStateRef state = C.getState(); 754 SValBuilder &svalBuilder = C.getSValBuilder(); 755 const LocationContext *LCtx = C.getLocationContext(); 756 SVal count = state->getSVal(CE->getArg(0), LCtx); 757 SVal elementSize = state->getSVal(CE->getArg(1), LCtx); 758 SVal TotalSize = svalBuilder.evalBinOp(state, BO_Mul, count, elementSize, 759 svalBuilder.getContext().getSizeType()); 760 SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy); 761 762 C.addTransition(MallocMemAux(C, CE, TotalSize, zeroVal, state)); 763} 764 765void MallocChecker::reportLeak(SymbolRef Sym, ExplodedNode *N, 766 CheckerContext &C) const { 767 assert(N); 768 if (!BT_Leak) { 769 BT_Leak.reset(new BuiltinBug("Memory leak", 770 "Allocated memory never released. Potential memory leak.")); 771 // Leaks should not be reported if they are post-dominated by a sink: 772 // (1) Sinks are higher importance bugs. 773 // (2) NoReturnFunctionChecker uses sink nodes to represent paths ending 774 // with __noreturn functions such as assert() or exit(). We choose not 775 // to report leaks on such paths. 776 BT_Leak->setSuppressOnSink(true); 777 } 778 779 BugReport *R = new BugReport(*BT_Leak, BT_Leak->getDescription(), N); 780 R->addVisitor(new MallocBugVisitor(Sym)); 781 C.EmitReport(R); 782} 783 784void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper, 785 CheckerContext &C) const 786{ 787 if (!SymReaper.hasDeadSymbols()) 788 return; 789 790 ProgramStateRef state = C.getState(); 791 RegionStateTy RS = state->get<RegionState>(); 792 RegionStateTy::Factory &F = state->get_context<RegionState>(); 793 794 bool generateReport = false; 795 llvm::SmallVector<SymbolRef, 2> Errors; 796 for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) { 797 if (SymReaper.isDead(I->first)) { 798 if (I->second.isAllocated()) { 799 generateReport = true; 800 Errors.push_back(I->first); 801 } 802 // Remove the dead symbol from the map. 803 RS = F.remove(RS, I->first); 804 805 } 806 } 807 808 // Cleanup the Realloc Pairs Map. 809 ReallocMap RP = state->get<ReallocPairs>(); 810 for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) { 811 if (SymReaper.isDead(I->first) || 812 SymReaper.isDead(I->second.ReallocatedSym)) { 813 state = state->remove<ReallocPairs>(I->first); 814 } 815 } 816 817 ExplodedNode *N = C.addTransition(state->set<RegionState>(RS)); 818 819 if (N && generateReport) { 820 for (llvm::SmallVector<SymbolRef, 2>::iterator 821 I = Errors.begin(), E = Errors.end(); I != E; ++I) { 822 reportLeak(*I, N, C); 823 } 824 } 825} 826 827void MallocChecker::checkEndPath(CheckerContext &C) const { 828 ProgramStateRef state = C.getState(); 829 RegionStateTy M = state->get<RegionState>(); 830 831 for (RegionStateTy::iterator I = M.begin(), E = M.end(); I != E; ++I) { 832 RefState RS = I->second; 833 if (RS.isAllocated()) { 834 ExplodedNode *N = C.addTransition(state); 835 if (N) 836 reportLeak(I->first, N, C); 837 } 838 } 839} 840 841bool MallocChecker::checkEscape(SymbolRef Sym, const Stmt *S, 842 CheckerContext &C) const { 843 ProgramStateRef state = C.getState(); 844 const RefState *RS = state->get<RegionState>(Sym); 845 if (!RS) 846 return false; 847 848 if (RS->isAllocated()) { 849 state = state->set<RegionState>(Sym, RefState::getEscaped(S)); 850 C.addTransition(state); 851 return true; 852 } 853 return false; 854} 855 856void MallocChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const { 857 if (isMemFunction(C.getCalleeDecl(CE), C.getASTContext())) 858 return; 859 860 // Check use after free, when a freed pointer is passed to a call. 861 ProgramStateRef State = C.getState(); 862 for (CallExpr::const_arg_iterator I = CE->arg_begin(), 863 E = CE->arg_end(); I != E; ++I) { 864 const Expr *A = *I; 865 if (A->getType().getTypePtr()->isAnyPointerType()) { 866 SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol(); 867 if (!Sym) 868 continue; 869 if (checkUseAfterFree(Sym, C, A)) 870 return; 871 } 872 } 873} 874 875void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const { 876 const Expr *E = S->getRetValue(); 877 if (!E) 878 return; 879 880 // Check if we are returning a symbol. 881 SymbolRef Sym = C.getState()->getSVal(E, C.getLocationContext()).getAsSymbol(); 882 if (!Sym) 883 return; 884 885 // Check if we are returning freed memory. 886 if (checkUseAfterFree(Sym, C, E)) 887 return; 888 889 // Check if the symbol is escaping. 890 checkEscape(Sym, E, C); 891} 892 893bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C, 894 const Stmt *S) const { 895 assert(Sym); 896 const RefState *RS = C.getState()->get<RegionState>(Sym); 897 if (RS && RS->isReleased()) { 898 if (ExplodedNode *N = C.generateSink()) { 899 if (!BT_UseFree) 900 BT_UseFree.reset(new BuiltinBug("Use of dynamically allocated memory " 901 "after it is freed.")); 902 903 BugReport *R = new BugReport(*BT_UseFree, BT_UseFree->getDescription(),N); 904 if (S) 905 R->addRange(S->getSourceRange()); 906 R->addVisitor(new MallocBugVisitor(Sym)); 907 C.EmitReport(R); 908 return true; 909 } 910 } 911 return false; 912} 913 914// Check if the location is a freed symbolic region. 915void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S, 916 CheckerContext &C) const { 917 SymbolRef Sym = l.getLocSymbolInBase(); 918 if (Sym) 919 checkUseAfterFree(Sym, C); 920} 921 922//===----------------------------------------------------------------------===// 923// Check various ways a symbol can be invalidated. 924// TODO: This logic (the next 3 functions) is copied/similar to the 925// RetainRelease checker. We might want to factor this out. 926//===----------------------------------------------------------------------===// 927 928// Stop tracking symbols when a value escapes as a result of checkBind. 929// A value escapes in three possible cases: 930// (1) we are binding to something that is not a memory region. 931// (2) we are binding to a memregion that does not have stack storage 932// (3) we are binding to a memregion with stack storage that the store 933// does not understand. 934void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S, 935 CheckerContext &C) const { 936 // Are we storing to something that causes the value to "escape"? 937 bool escapes = true; 938 ProgramStateRef state = C.getState(); 939 940 if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) { 941 escapes = !regionLoc->getRegion()->hasStackStorage(); 942 943 if (!escapes) { 944 // To test (3), generate a new state with the binding added. If it is 945 // the same state, then it escapes (since the store cannot represent 946 // the binding). 947 escapes = (state == (state->bindLoc(*regionLoc, val))); 948 } 949 if (!escapes) { 950 // Case 4: We do not currently model what happens when a symbol is 951 // assigned to a struct field, so be conservative here and let the symbol 952 // go. TODO: This could definitely be improved upon. 953 escapes = !isa<VarRegion>(regionLoc->getRegion()); 954 } 955 } 956 957 // If our store can represent the binding and we aren't storing to something 958 // that doesn't have local storage then just return and have the simulation 959 // state continue as is. 960 if (!escapes) 961 return; 962 963 // Otherwise, find all symbols referenced by 'val' that we are tracking 964 // and stop tracking them. 965 state = state->scanReachableSymbols<StopTrackingCallback>(val).getState(); 966 C.addTransition(state); 967} 968 969// If a symbolic region is assumed to NULL (or another constant), stop tracking 970// it - assuming that allocation failed on this path. 971ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state, 972 SVal Cond, 973 bool Assumption) const { 974 RegionStateTy RS = state->get<RegionState>(); 975 for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) { 976 // If the symbol is assumed to NULL or another constant, this will 977 // return an APSInt*. 978 if (state->getSymVal(I.getKey())) 979 state = state->remove<RegionState>(I.getKey()); 980 } 981 982 // Realloc returns 0 when reallocation fails, which means that we should 983 // restore the state of the pointer being reallocated. 984 ReallocMap RP = state->get<ReallocPairs>(); 985 for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) { 986 // If the symbol is assumed to NULL or another constant, this will 987 // return an APSInt*. 988 if (state->getSymVal(I.getKey())) { 989 SymbolRef ReallocSym = I.getData().ReallocatedSym; 990 const RefState *RS = state->get<RegionState>(ReallocSym); 991 if (RS) { 992 if (RS->isReleased() && ! I.getData().IsFreeOnFailure) 993 state = state->set<RegionState>(ReallocSym, 994 RefState::getAllocateUnchecked(RS->getStmt())); 995 } 996 state = state->remove<ReallocPairs>(I.getKey()); 997 } 998 } 999 1000 return state; 1001} 1002 1003// Check if the function is not known to us. So, for example, we could 1004// conservatively assume it can free/reallocate it's pointer arguments. 1005// (We assume that the pointers cannot escape through calls to system 1006// functions not handled by this checker.) 1007bool MallocChecker::hasUnknownBehavior(const FunctionDecl *FD, 1008 ProgramStateRef State) const { 1009 ASTContext &ASTC = State->getStateManager().getContext(); 1010 1011 // If it's one of the allocation functions we can reason about, we model it's 1012 // behavior explicitly. 1013 if (isMemFunction(FD, ASTC)) { 1014 return false; 1015 } 1016 1017 // If it's a system call, we know it does not free the memory. 1018 SourceManager &SM = ASTC.getSourceManager(); 1019 if (SM.isInSystemHeader(FD->getLocation())) { 1020 return false; 1021 } 1022 1023 // Otherwise, assume that the function can free memory. 1024 return true; 1025} 1026 1027// If the symbol we are tracking is invalidated, but not explicitly (ex: the &p 1028// escapes, when we are tracking p), do not track the symbol as we cannot reason 1029// about it anymore. 1030ProgramStateRef 1031MallocChecker::checkRegionChanges(ProgramStateRef State, 1032 const StoreManager::InvalidatedSymbols *invalidated, 1033 ArrayRef<const MemRegion *> ExplicitRegions, 1034 ArrayRef<const MemRegion *> Regions, 1035 const CallOrObjCMessage *Call) const { 1036 if (!invalidated) 1037 return State; 1038 llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols; 1039 1040 const FunctionDecl *FD = (Call ? 1041 dyn_cast_or_null<FunctionDecl>(Call->getDecl()) :0); 1042 1043 // If it's a call which might free or reallocate memory, we assume that all 1044 // regions (explicit and implicit) escaped. Otherwise, whitelist explicit 1045 // pointers; we still can track them. 1046 if (!(FD && hasUnknownBehavior(FD, State))) { 1047 for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(), 1048 E = ExplicitRegions.end(); I != E; ++I) { 1049 if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>()) 1050 WhitelistedSymbols.insert(R->getSymbol()); 1051 } 1052 } 1053 1054 for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(), 1055 E = invalidated->end(); I!=E; ++I) { 1056 SymbolRef sym = *I; 1057 if (WhitelistedSymbols.count(sym)) 1058 continue; 1059 // The symbol escaped. 1060 if (const RefState *RS = State->get<RegionState>(sym)) 1061 State = State->set<RegionState>(sym, RefState::getEscaped(RS->getStmt())); 1062 } 1063 return State; 1064} 1065 1066PathDiagnosticPiece * 1067MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N, 1068 const ExplodedNode *PrevN, 1069 BugReporterContext &BRC, 1070 BugReport &BR) { 1071 const RefState *RS = N->getState()->get<RegionState>(Sym); 1072 const RefState *RSPrev = PrevN->getState()->get<RegionState>(Sym); 1073 if (!RS && !RSPrev) 1074 return 0; 1075 1076 const Stmt *S = 0; 1077 const char *Msg = 0; 1078 1079 // Retrieve the associated statement. 1080 ProgramPoint ProgLoc = N->getLocation(); 1081 if (isa<StmtPoint>(ProgLoc)) 1082 S = cast<StmtPoint>(ProgLoc).getStmt(); 1083 // If an assumption was made on a branch, it should be caught 1084 // here by looking at the state transition. 1085 if (isa<BlockEdge>(ProgLoc)) { 1086 const CFGBlock *srcBlk = cast<BlockEdge>(ProgLoc).getSrc(); 1087 S = srcBlk->getTerminator(); 1088 } 1089 if (!S) 1090 return 0; 1091 1092 // Find out if this is an interesting point and what is the kind. 1093 if (Mode == Normal) { 1094 if (isAllocated(RS, RSPrev, S)) 1095 Msg = "Memory is allocated"; 1096 else if (isReleased(RS, RSPrev, S)) 1097 Msg = "Memory is released"; 1098 else if (isReallocFailedCheck(RS, RSPrev, S)) { 1099 Mode = ReallocationFailed; 1100 Msg = "Reallocation failed"; 1101 } 1102 1103 // We are in a special mode if a reallocation failed later in the path. 1104 } else if (Mode == ReallocationFailed) { 1105 // Generate a special diagnostic for the first realloc we find. 1106 if (!isAllocated(RS, RSPrev, S) && !isReleased(RS, RSPrev, S)) 1107 return 0; 1108 1109 // Check that the name of the function is realloc. 1110 const CallExpr *CE = dyn_cast<CallExpr>(S); 1111 if (!CE) 1112 return 0; 1113 const FunctionDecl *funDecl = CE->getDirectCallee(); 1114 if (!funDecl) 1115 return 0; 1116 StringRef FunName = funDecl->getName(); 1117 if (!(FunName.equals("realloc") || FunName.equals("reallocf"))) 1118 return 0; 1119 Msg = "Attempt to reallocate memory"; 1120 Mode = Normal; 1121 } 1122 1123 if (!Msg) 1124 return 0; 1125 1126 // Generate the extra diagnostic. 1127 PathDiagnosticLocation Pos(S, BRC.getSourceManager(), 1128 N->getLocationContext()); 1129 return new PathDiagnosticEventPiece(Pos, Msg); 1130} 1131 1132 1133#define REGISTER_CHECKER(name) \ 1134void ento::register##name(CheckerManager &mgr) {\ 1135 mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\ 1136} 1137 1138REGISTER_CHECKER(MallocPessimistic) 1139REGISTER_CHECKER(MallocOptimistic) 1140