1 //= CStringChecker.cpp - Checks calls to C string functions --------*- C++ -*-//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This defines CStringChecker, which is an assortment of checks on calls
11 // to functions in <string.h>.
13 //===----------------------------------------------------------------------===//
15 #include "ClangSACheckers.h"
16 #include "InterCheckerAPI.h"
17 #include "clang/Basic/CharInfo.h"
18 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
19 #include "clang/StaticAnalyzer/Core/Checker.h"
20 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
21 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
22 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
23 #include "llvm/ADT/STLExtras.h"
24 #include "llvm/ADT/SmallString.h"
25 #include "llvm/ADT/StringSwitch.h"
26 #include "llvm/Support/raw_ostream.h"
28 using namespace clang;
32 class CStringChecker : public Checker< eval::Call,
33 check::PreStmt<DeclStmt>,
38 mutable std::unique_ptr<BugType> BT_Null, BT_Bounds, BT_Overlap,
39 BT_NotCString, BT_AdditionOverflow;
41 mutable const char *CurrentFunctionDescription;
44 /// The filter is used to filter out the diagnostics which are not enabled by
46 struct CStringChecksFilter {
47 DefaultBool CheckCStringNullArg;
48 DefaultBool CheckCStringOutOfBounds;
49 DefaultBool CheckCStringBufferOverlap;
50 DefaultBool CheckCStringNotNullTerm;
52 CheckName CheckNameCStringNullArg;
53 CheckName CheckNameCStringOutOfBounds;
54 CheckName CheckNameCStringBufferOverlap;
55 CheckName CheckNameCStringNotNullTerm;
58 CStringChecksFilter Filter;
60 static void *getTag() { static int tag; return &tag; }
62 bool evalCall(const CallExpr *CE, CheckerContext &C) const;
63 void checkPreStmt(const DeclStmt *DS, CheckerContext &C) const;
64 void checkLiveSymbols(ProgramStateRef state, SymbolReaper &SR) const;
65 void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;
66 bool wantsRegionChangeUpdate(ProgramStateRef state) const;
69 checkRegionChanges(ProgramStateRef state,
70 const InvalidatedSymbols *,
71 ArrayRef<const MemRegion *> ExplicitRegions,
72 ArrayRef<const MemRegion *> Regions,
73 const CallEvent *Call) const;
75 typedef void (CStringChecker::*FnCheck)(CheckerContext &,
76 const CallExpr *) const;
78 void evalMemcpy(CheckerContext &C, const CallExpr *CE) const;
79 void evalMempcpy(CheckerContext &C, const CallExpr *CE) const;
80 void evalMemmove(CheckerContext &C, const CallExpr *CE) const;
81 void evalBcopy(CheckerContext &C, const CallExpr *CE) const;
82 void evalCopyCommon(CheckerContext &C, const CallExpr *CE,
83 ProgramStateRef state,
87 bool Restricted = false,
88 bool IsMempcpy = false) const;
90 void evalMemcmp(CheckerContext &C, const CallExpr *CE) const;
92 void evalstrLength(CheckerContext &C, const CallExpr *CE) const;
93 void evalstrnLength(CheckerContext &C, const CallExpr *CE) const;
94 void evalstrLengthCommon(CheckerContext &C,
96 bool IsStrnlen = false) const;
98 void evalStrcpy(CheckerContext &C, const CallExpr *CE) const;
99 void evalStrncpy(CheckerContext &C, const CallExpr *CE) const;
100 void evalStpcpy(CheckerContext &C, const CallExpr *CE) const;
101 void evalStrcpyCommon(CheckerContext &C,
105 bool isAppending) const;
107 void evalStrcat(CheckerContext &C, const CallExpr *CE) const;
108 void evalStrncat(CheckerContext &C, const CallExpr *CE) const;
110 void evalStrcmp(CheckerContext &C, const CallExpr *CE) const;
111 void evalStrncmp(CheckerContext &C, const CallExpr *CE) const;
112 void evalStrcasecmp(CheckerContext &C, const CallExpr *CE) const;
113 void evalStrncasecmp(CheckerContext &C, const CallExpr *CE) const;
114 void evalStrcmpCommon(CheckerContext &C,
116 bool isBounded = false,
117 bool ignoreCase = false) const;
119 void evalStrsep(CheckerContext &C, const CallExpr *CE) const;
122 std::pair<ProgramStateRef , ProgramStateRef >
123 static assumeZero(CheckerContext &C,
124 ProgramStateRef state, SVal V, QualType Ty);
126 static ProgramStateRef setCStringLength(ProgramStateRef state,
129 static SVal getCStringLengthForRegion(CheckerContext &C,
130 ProgramStateRef &state,
134 SVal getCStringLength(CheckerContext &C,
135 ProgramStateRef &state,
138 bool hypothetical = false) const;
140 const StringLiteral *getCStringLiteral(CheckerContext &C,
141 ProgramStateRef &state,
145 static ProgramStateRef InvalidateBuffer(CheckerContext &C,
146 ProgramStateRef state,
147 const Expr *Ex, SVal V,
148 bool IsSourceBuffer);
150 static bool SummarizeRegion(raw_ostream &os, ASTContext &Ctx,
151 const MemRegion *MR);
154 ProgramStateRef checkNonNull(CheckerContext &C,
155 ProgramStateRef state,
158 ProgramStateRef CheckLocation(CheckerContext &C,
159 ProgramStateRef state,
162 const char *message = nullptr) const;
163 ProgramStateRef CheckBufferAccess(CheckerContext &C,
164 ProgramStateRef state,
166 const Expr *FirstBuf,
167 const Expr *SecondBuf,
168 const char *firstMessage = nullptr,
169 const char *secondMessage = nullptr,
170 bool WarnAboutSize = false) const;
172 ProgramStateRef CheckBufferAccess(CheckerContext &C,
173 ProgramStateRef state,
176 const char *message = nullptr,
177 bool WarnAboutSize = false) const {
178 // This is a convenience override.
179 return CheckBufferAccess(C, state, Size, Buf, nullptr, message, nullptr,
182 ProgramStateRef CheckOverlap(CheckerContext &C,
183 ProgramStateRef state,
186 const Expr *Second) const;
187 void emitOverlapBug(CheckerContext &C,
188 ProgramStateRef state,
190 const Stmt *Second) const;
192 ProgramStateRef checkAdditionOverflow(CheckerContext &C,
193 ProgramStateRef state,
198 } //end anonymous namespace
200 REGISTER_MAP_WITH_PROGRAMSTATE(CStringLength, const MemRegion *, SVal)
202 //===----------------------------------------------------------------------===//
203 // Individual checks and utility methods.
204 //===----------------------------------------------------------------------===//
206 std::pair<ProgramStateRef , ProgramStateRef >
207 CStringChecker::assumeZero(CheckerContext &C, ProgramStateRef state, SVal V,
209 Optional<DefinedSVal> val = V.getAs<DefinedSVal>();
211 return std::pair<ProgramStateRef , ProgramStateRef >(state, state);
213 SValBuilder &svalBuilder = C.getSValBuilder();
214 DefinedOrUnknownSVal zero = svalBuilder.makeZeroVal(Ty);
215 return state->assume(svalBuilder.evalEQ(state, *val, zero));
218 ProgramStateRef CStringChecker::checkNonNull(CheckerContext &C,
219 ProgramStateRef state,
220 const Expr *S, SVal l) const {
221 // If a previous check has failed, propagate the failure.
225 ProgramStateRef stateNull, stateNonNull;
226 std::tie(stateNull, stateNonNull) = assumeZero(C, state, l, S->getType());
228 if (stateNull && !stateNonNull) {
229 if (!Filter.CheckCStringNullArg)
232 ExplodedNode *N = C.generateSink(stateNull);
237 BT_Null.reset(new BuiltinBug(
238 Filter.CheckNameCStringNullArg, categories::UnixAPI,
239 "Null pointer argument in call to byte string function"));
242 llvm::raw_svector_ostream os(buf);
243 assert(CurrentFunctionDescription);
244 os << "Null pointer argument in call to " << CurrentFunctionDescription;
246 // Generate a report for this bug.
247 BuiltinBug *BT = static_cast<BuiltinBug*>(BT_Null.get());
248 BugReport *report = new BugReport(*BT, os.str(), N);
250 report->addRange(S->getSourceRange());
251 bugreporter::trackNullOrUndefValue(N, S, *report);
252 C.emitReport(report);
256 // From here on, assume that the value is non-null.
257 assert(stateNonNull);
261 // FIXME: This was originally copied from ArrayBoundChecker.cpp. Refactor?
262 ProgramStateRef CStringChecker::CheckLocation(CheckerContext &C,
263 ProgramStateRef state,
264 const Expr *S, SVal l,
265 const char *warningMsg) const {
266 // If a previous check has failed, propagate the failure.
270 // Check for out of bound array element access.
271 const MemRegion *R = l.getAsRegion();
275 const ElementRegion *ER = dyn_cast<ElementRegion>(R);
279 assert(ER->getValueType() == C.getASTContext().CharTy &&
280 "CheckLocation should only be called with char* ElementRegions");
282 // Get the size of the array.
283 const SubRegion *superReg = cast<SubRegion>(ER->getSuperRegion());
284 SValBuilder &svalBuilder = C.getSValBuilder();
286 svalBuilder.convertToArrayIndex(superReg->getExtent(svalBuilder));
287 DefinedOrUnknownSVal Size = Extent.castAs<DefinedOrUnknownSVal>();
289 // Get the index of the accessed element.
290 DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>();
292 ProgramStateRef StInBound = state->assumeInBound(Idx, Size, true);
293 ProgramStateRef StOutBound = state->assumeInBound(Idx, Size, false);
294 if (StOutBound && !StInBound) {
295 ExplodedNode *N = C.generateSink(StOutBound);
300 BT_Bounds.reset(new BuiltinBug(
301 Filter.CheckNameCStringOutOfBounds, "Out-of-bound array access",
302 "Byte string function accesses out-of-bound array element"));
304 BuiltinBug *BT = static_cast<BuiltinBug*>(BT_Bounds.get());
306 // Generate a report for this bug.
309 report = new BugReport(*BT, warningMsg, N);
311 assert(CurrentFunctionDescription);
312 assert(CurrentFunctionDescription[0] != '\0');
315 llvm::raw_svector_ostream os(buf);
316 os << toUppercase(CurrentFunctionDescription[0])
317 << &CurrentFunctionDescription[1]
318 << " accesses out-of-bound array element";
319 report = new BugReport(*BT, os.str(), N);
322 // FIXME: It would be nice to eventually make this diagnostic more clear,
323 // e.g., by referencing the original declaration or by saying *why* this
324 // reference is outside the range.
326 report->addRange(S->getSourceRange());
327 C.emitReport(report);
331 // Array bound check succeeded. From this point forward the array bound
332 // should always succeed.
336 ProgramStateRef CStringChecker::CheckBufferAccess(CheckerContext &C,
337 ProgramStateRef state,
339 const Expr *FirstBuf,
340 const Expr *SecondBuf,
341 const char *firstMessage,
342 const char *secondMessage,
343 bool WarnAboutSize) const {
344 // If a previous check has failed, propagate the failure.
348 SValBuilder &svalBuilder = C.getSValBuilder();
349 ASTContext &Ctx = svalBuilder.getContext();
350 const LocationContext *LCtx = C.getLocationContext();
352 QualType sizeTy = Size->getType();
353 QualType PtrTy = Ctx.getPointerType(Ctx.CharTy);
355 // Check that the first buffer is non-null.
356 SVal BufVal = state->getSVal(FirstBuf, LCtx);
357 state = checkNonNull(C, state, FirstBuf, BufVal);
361 // If out-of-bounds checking is turned off, skip the rest.
362 if (!Filter.CheckCStringOutOfBounds)
365 // Get the access length and make sure it is known.
366 // FIXME: This assumes the caller has already checked that the access length
367 // is positive. And that it's unsigned.
368 SVal LengthVal = state->getSVal(Size, LCtx);
369 Optional<NonLoc> Length = LengthVal.getAs<NonLoc>();
373 // Compute the offset of the last element to be accessed: size-1.
374 NonLoc One = svalBuilder.makeIntVal(1, sizeTy).castAs<NonLoc>();
375 NonLoc LastOffset = svalBuilder
376 .evalBinOpNN(state, BO_Sub, *Length, One, sizeTy).castAs<NonLoc>();
378 // Check that the first buffer is sufficiently long.
379 SVal BufStart = svalBuilder.evalCast(BufVal, PtrTy, FirstBuf->getType());
380 if (Optional<Loc> BufLoc = BufStart.getAs<Loc>()) {
381 const Expr *warningExpr = (WarnAboutSize ? Size : FirstBuf);
383 SVal BufEnd = svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc,
385 state = CheckLocation(C, state, warningExpr, BufEnd, firstMessage);
387 // If the buffer isn't large enough, abort.
392 // If there's a second buffer, check it as well.
394 BufVal = state->getSVal(SecondBuf, LCtx);
395 state = checkNonNull(C, state, SecondBuf, BufVal);
399 BufStart = svalBuilder.evalCast(BufVal, PtrTy, SecondBuf->getType());
400 if (Optional<Loc> BufLoc = BufStart.getAs<Loc>()) {
401 const Expr *warningExpr = (WarnAboutSize ? Size : SecondBuf);
403 SVal BufEnd = svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc,
405 state = CheckLocation(C, state, warningExpr, BufEnd, secondMessage);
409 // Large enough or not, return this state!
413 ProgramStateRef CStringChecker::CheckOverlap(CheckerContext &C,
414 ProgramStateRef state,
417 const Expr *Second) const {
418 if (!Filter.CheckCStringBufferOverlap)
421 // Do a simple check for overlap: if the two arguments are from the same
422 // buffer, see if the end of the first is greater than the start of the second
425 // If a previous check has failed, propagate the failure.
429 ProgramStateRef stateTrue, stateFalse;
431 // Get the buffer values and make sure they're known locations.
432 const LocationContext *LCtx = C.getLocationContext();
433 SVal firstVal = state->getSVal(First, LCtx);
434 SVal secondVal = state->getSVal(Second, LCtx);
436 Optional<Loc> firstLoc = firstVal.getAs<Loc>();
440 Optional<Loc> secondLoc = secondVal.getAs<Loc>();
444 // Are the two values the same?
445 SValBuilder &svalBuilder = C.getSValBuilder();
446 std::tie(stateTrue, stateFalse) =
447 state->assume(svalBuilder.evalEQ(state, *firstLoc, *secondLoc));
449 if (stateTrue && !stateFalse) {
450 // If the values are known to be equal, that's automatically an overlap.
451 emitOverlapBug(C, stateTrue, First, Second);
455 // assume the two expressions are not equal.
459 // Which value comes first?
460 QualType cmpTy = svalBuilder.getConditionType();
461 SVal reverse = svalBuilder.evalBinOpLL(state, BO_GT,
462 *firstLoc, *secondLoc, cmpTy);
463 Optional<DefinedOrUnknownSVal> reverseTest =
464 reverse.getAs<DefinedOrUnknownSVal>();
468 std::tie(stateTrue, stateFalse) = state->assume(*reverseTest);
471 // If we don't know which one comes first, we can't perform this test.
474 // Switch the values so that firstVal is before secondVal.
475 std::swap(firstLoc, secondLoc);
477 // Switch the Exprs as well, so that they still correspond.
478 std::swap(First, Second);
482 // Get the length, and make sure it too is known.
483 SVal LengthVal = state->getSVal(Size, LCtx);
484 Optional<NonLoc> Length = LengthVal.getAs<NonLoc>();
488 // Convert the first buffer's start address to char*.
489 // Bail out if the cast fails.
490 ASTContext &Ctx = svalBuilder.getContext();
491 QualType CharPtrTy = Ctx.getPointerType(Ctx.CharTy);
492 SVal FirstStart = svalBuilder.evalCast(*firstLoc, CharPtrTy,
494 Optional<Loc> FirstStartLoc = FirstStart.getAs<Loc>();
498 // Compute the end of the first buffer. Bail out if THAT fails.
499 SVal FirstEnd = svalBuilder.evalBinOpLN(state, BO_Add,
500 *FirstStartLoc, *Length, CharPtrTy);
501 Optional<Loc> FirstEndLoc = FirstEnd.getAs<Loc>();
505 // Is the end of the first buffer past the start of the second buffer?
506 SVal Overlap = svalBuilder.evalBinOpLL(state, BO_GT,
507 *FirstEndLoc, *secondLoc, cmpTy);
508 Optional<DefinedOrUnknownSVal> OverlapTest =
509 Overlap.getAs<DefinedOrUnknownSVal>();
513 std::tie(stateTrue, stateFalse) = state->assume(*OverlapTest);
515 if (stateTrue && !stateFalse) {
517 emitOverlapBug(C, stateTrue, First, Second);
521 // assume the two expressions don't overlap.
526 void CStringChecker::emitOverlapBug(CheckerContext &C, ProgramStateRef state,
527 const Stmt *First, const Stmt *Second) const {
528 ExplodedNode *N = C.generateSink(state);
533 BT_Overlap.reset(new BugType(Filter.CheckNameCStringBufferOverlap,
534 categories::UnixAPI, "Improper arguments"));
536 // Generate a report for this bug.
538 new BugReport(*BT_Overlap,
539 "Arguments must not be overlapping buffers", N);
540 report->addRange(First->getSourceRange());
541 report->addRange(Second->getSourceRange());
543 C.emitReport(report);
546 ProgramStateRef CStringChecker::checkAdditionOverflow(CheckerContext &C,
547 ProgramStateRef state,
549 NonLoc right) const {
550 // If out-of-bounds checking is turned off, skip the rest.
551 if (!Filter.CheckCStringOutOfBounds)
554 // If a previous check has failed, propagate the failure.
558 SValBuilder &svalBuilder = C.getSValBuilder();
559 BasicValueFactory &BVF = svalBuilder.getBasicValueFactory();
561 QualType sizeTy = svalBuilder.getContext().getSizeType();
562 const llvm::APSInt &maxValInt = BVF.getMaxValue(sizeTy);
563 NonLoc maxVal = svalBuilder.makeIntVal(maxValInt);
566 if (right.getAs<nonloc::ConcreteInt>()) {
567 maxMinusRight = svalBuilder.evalBinOpNN(state, BO_Sub, maxVal, right,
570 // Try switching the operands. (The order of these two assignments is
572 maxMinusRight = svalBuilder.evalBinOpNN(state, BO_Sub, maxVal, left,
577 if (Optional<NonLoc> maxMinusRightNL = maxMinusRight.getAs<NonLoc>()) {
578 QualType cmpTy = svalBuilder.getConditionType();
579 // If left > max - right, we have an overflow.
580 SVal willOverflow = svalBuilder.evalBinOpNN(state, BO_GT, left,
581 *maxMinusRightNL, cmpTy);
583 ProgramStateRef stateOverflow, stateOkay;
584 std::tie(stateOverflow, stateOkay) =
585 state->assume(willOverflow.castAs<DefinedOrUnknownSVal>());
587 if (stateOverflow && !stateOkay) {
588 // We have an overflow. Emit a bug report.
589 ExplodedNode *N = C.generateSink(stateOverflow);
593 if (!BT_AdditionOverflow)
594 BT_AdditionOverflow.reset(
595 new BuiltinBug(Filter.CheckNameCStringOutOfBounds, "API",
596 "Sum of expressions causes overflow"));
598 // This isn't a great error message, but this should never occur in real
599 // code anyway -- you'd have to create a buffer longer than a size_t can
600 // represent, which is sort of a contradiction.
601 const char *warning =
602 "This expression will create a string whose length is too big to "
603 "be represented as a size_t";
605 // Generate a report for this bug.
606 BugReport *report = new BugReport(*BT_AdditionOverflow, warning, N);
607 C.emitReport(report);
612 // From now on, assume an overflow didn't occur.
620 ProgramStateRef CStringChecker::setCStringLength(ProgramStateRef state,
623 assert(!strLength.isUndef() && "Attempt to set an undefined string length");
625 MR = MR->StripCasts();
627 switch (MR->getKind()) {
628 case MemRegion::StringRegionKind:
629 // FIXME: This can happen if we strcpy() into a string region. This is
630 // undefined [C99 6.4.5p6], but we should still warn about it.
633 case MemRegion::SymbolicRegionKind:
634 case MemRegion::AllocaRegionKind:
635 case MemRegion::VarRegionKind:
636 case MemRegion::FieldRegionKind:
637 case MemRegion::ObjCIvarRegionKind:
638 // These are the types we can currently track string lengths for.
641 case MemRegion::ElementRegionKind:
642 // FIXME: Handle element regions by upper-bounding the parent region's
647 // Other regions (mostly non-data) can't have a reliable C string length.
648 // For now, just ignore the change.
649 // FIXME: These are rare but not impossible. We should output some kind of
650 // warning for things like strcpy((char[]){'a', 0}, "b");
654 if (strLength.isUnknown())
655 return state->remove<CStringLength>(MR);
657 return state->set<CStringLength>(MR, strLength);
660 SVal CStringChecker::getCStringLengthForRegion(CheckerContext &C,
661 ProgramStateRef &state,
666 // If there's a recorded length, go ahead and return it.
667 const SVal *Recorded = state->get<CStringLength>(MR);
672 // Otherwise, get a new symbol and update the state.
673 SValBuilder &svalBuilder = C.getSValBuilder();
674 QualType sizeTy = svalBuilder.getContext().getSizeType();
675 SVal strLength = svalBuilder.getMetadataSymbolVal(CStringChecker::getTag(),
680 if (Optional<NonLoc> strLn = strLength.getAs<NonLoc>()) {
681 // In case of unbounded calls strlen etc bound the range to SIZE_MAX/4
682 BasicValueFactory &BVF = svalBuilder.getBasicValueFactory();
683 const llvm::APSInt &maxValInt = BVF.getMaxValue(sizeTy);
684 llvm::APSInt fourInt = APSIntType(maxValInt).getValue(4);
685 const llvm::APSInt *maxLengthInt = BVF.evalAPSInt(BO_Div, maxValInt,
687 NonLoc maxLength = svalBuilder.makeIntVal(*maxLengthInt);
688 SVal evalLength = svalBuilder.evalBinOpNN(state, BO_LE, *strLn,
690 state = state->assume(evalLength.castAs<DefinedOrUnknownSVal>(), true);
692 state = state->set<CStringLength>(MR, strLength);
698 SVal CStringChecker::getCStringLength(CheckerContext &C, ProgramStateRef &state,
699 const Expr *Ex, SVal Buf,
700 bool hypothetical) const {
701 const MemRegion *MR = Buf.getAsRegion();
703 // If we can't get a region, see if it's something we /know/ isn't a
704 // C string. In the context of locations, the only time we can issue such
705 // a warning is for labels.
706 if (Optional<loc::GotoLabel> Label = Buf.getAs<loc::GotoLabel>()) {
707 if (!Filter.CheckCStringNotNullTerm)
708 return UndefinedVal();
710 if (ExplodedNode *N = C.addTransition(state)) {
712 BT_NotCString.reset(new BuiltinBug(
713 Filter.CheckNameCStringNotNullTerm, categories::UnixAPI,
714 "Argument is not a null-terminated string."));
716 SmallString<120> buf;
717 llvm::raw_svector_ostream os(buf);
718 assert(CurrentFunctionDescription);
719 os << "Argument to " << CurrentFunctionDescription
720 << " is the address of the label '" << Label->getLabel()->getName()
721 << "', which is not a null-terminated string";
723 // Generate a report for this bug.
724 BugReport *report = new BugReport(*BT_NotCString, os.str(), N);
726 report->addRange(Ex->getSourceRange());
727 C.emitReport(report);
729 return UndefinedVal();
733 // If it's not a region and not a label, give up.
737 // If we have a region, strip casts from it and see if we can figure out
738 // its length. For anything we can't figure out, just return UnknownVal.
739 MR = MR->StripCasts();
741 switch (MR->getKind()) {
742 case MemRegion::StringRegionKind: {
743 // Modifying the contents of string regions is undefined [C99 6.4.5p6],
744 // so we can assume that the byte length is the correct C string length.
745 SValBuilder &svalBuilder = C.getSValBuilder();
746 QualType sizeTy = svalBuilder.getContext().getSizeType();
747 const StringLiteral *strLit = cast<StringRegion>(MR)->getStringLiteral();
748 return svalBuilder.makeIntVal(strLit->getByteLength(), sizeTy);
750 case MemRegion::SymbolicRegionKind:
751 case MemRegion::AllocaRegionKind:
752 case MemRegion::VarRegionKind:
753 case MemRegion::FieldRegionKind:
754 case MemRegion::ObjCIvarRegionKind:
755 return getCStringLengthForRegion(C, state, Ex, MR, hypothetical);
756 case MemRegion::CompoundLiteralRegionKind:
757 // FIXME: Can we track this? Is it necessary?
759 case MemRegion::ElementRegionKind:
760 // FIXME: How can we handle this? It's not good enough to subtract the
761 // offset from the base string length; consider "123\x00567" and &a[5].
764 // Other regions (mostly non-data) can't have a reliable C string length.
765 // In this case, an error is emitted and UndefinedVal is returned.
766 // The caller should always be prepared to handle this case.
767 if (!Filter.CheckCStringNotNullTerm)
768 return UndefinedVal();
770 if (ExplodedNode *N = C.addTransition(state)) {
772 BT_NotCString.reset(new BuiltinBug(
773 Filter.CheckNameCStringNotNullTerm, categories::UnixAPI,
774 "Argument is not a null-terminated string."));
776 SmallString<120> buf;
777 llvm::raw_svector_ostream os(buf);
779 assert(CurrentFunctionDescription);
780 os << "Argument to " << CurrentFunctionDescription << " is ";
782 if (SummarizeRegion(os, C.getASTContext(), MR))
783 os << ", which is not a null-terminated string";
785 os << "not a null-terminated string";
787 // Generate a report for this bug.
788 BugReport *report = new BugReport(*BT_NotCString,
791 report->addRange(Ex->getSourceRange());
792 C.emitReport(report);
795 return UndefinedVal();
799 const StringLiteral *CStringChecker::getCStringLiteral(CheckerContext &C,
800 ProgramStateRef &state, const Expr *expr, SVal val) const {
802 // Get the memory region pointed to by the val.
803 const MemRegion *bufRegion = val.getAsRegion();
807 // Strip casts off the memory region.
808 bufRegion = bufRegion->StripCasts();
810 // Cast the memory region to a string region.
811 const StringRegion *strRegion= dyn_cast<StringRegion>(bufRegion);
815 // Return the actual string in the string region.
816 return strRegion->getStringLiteral();
819 ProgramStateRef CStringChecker::InvalidateBuffer(CheckerContext &C,
820 ProgramStateRef state,
821 const Expr *E, SVal V,
822 bool IsSourceBuffer) {
823 Optional<Loc> L = V.getAs<Loc>();
827 // FIXME: This is a simplified version of what's in CFRefCount.cpp -- it makes
828 // some assumptions about the value that CFRefCount can't. Even so, it should
829 // probably be refactored.
830 if (Optional<loc::MemRegionVal> MR = L->getAs<loc::MemRegionVal>()) {
831 const MemRegion *R = MR->getRegion()->StripCasts();
833 // Are we dealing with an ElementRegion? If so, we should be invalidating
835 if (const ElementRegion *ER = dyn_cast<ElementRegion>(R)) {
836 R = ER->getSuperRegion();
837 // FIXME: What about layers of ElementRegions?
840 // Invalidate this region.
841 const LocationContext *LCtx = C.getPredecessor()->getLocationContext();
843 bool CausesPointerEscape = false;
844 RegionAndSymbolInvalidationTraits ITraits;
845 // Invalidate and escape only indirect regions accessible through the source
847 if (IsSourceBuffer) {
849 RegionAndSymbolInvalidationTraits::TK_PreserveContents);
850 ITraits.setTrait(R, RegionAndSymbolInvalidationTraits::TK_SuppressEscape);
851 CausesPointerEscape = true;
854 return state->invalidateRegions(R, E, C.blockCount(), LCtx,
855 CausesPointerEscape, nullptr, nullptr,
859 // If we have a non-region value by chance, just remove the binding.
860 // FIXME: is this necessary or correct? This handles the non-Region
861 // cases. Is it ever valid to store to these?
862 return state->killBinding(*L);
865 bool CStringChecker::SummarizeRegion(raw_ostream &os, ASTContext &Ctx,
866 const MemRegion *MR) {
867 const TypedValueRegion *TVR = dyn_cast<TypedValueRegion>(MR);
869 switch (MR->getKind()) {
870 case MemRegion::FunctionTextRegionKind: {
871 const NamedDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
873 os << "the address of the function '" << *FD << '\'';
875 os << "the address of a function";
878 case MemRegion::BlockTextRegionKind:
881 case MemRegion::BlockDataRegionKind:
884 case MemRegion::CXXThisRegionKind:
885 case MemRegion::CXXTempObjectRegionKind:
886 os << "a C++ temp object of type " << TVR->getValueType().getAsString();
888 case MemRegion::VarRegionKind:
889 os << "a variable of type" << TVR->getValueType().getAsString();
891 case MemRegion::FieldRegionKind:
892 os << "a field of type " << TVR->getValueType().getAsString();
894 case MemRegion::ObjCIvarRegionKind:
895 os << "an instance variable of type " << TVR->getValueType().getAsString();
902 //===----------------------------------------------------------------------===//
903 // evaluation of individual function calls.
904 //===----------------------------------------------------------------------===//
906 void CStringChecker::evalCopyCommon(CheckerContext &C,
908 ProgramStateRef state,
909 const Expr *Size, const Expr *Dest,
910 const Expr *Source, bool Restricted,
911 bool IsMempcpy) const {
912 CurrentFunctionDescription = "memory copy function";
914 // See if the size argument is zero.
915 const LocationContext *LCtx = C.getLocationContext();
916 SVal sizeVal = state->getSVal(Size, LCtx);
917 QualType sizeTy = Size->getType();
919 ProgramStateRef stateZeroSize, stateNonZeroSize;
920 std::tie(stateZeroSize, stateNonZeroSize) =
921 assumeZero(C, state, sizeVal, sizeTy);
923 // Get the value of the Dest.
924 SVal destVal = state->getSVal(Dest, LCtx);
926 // If the size is zero, there won't be any actual memory access, so
927 // just bind the return value to the destination buffer and return.
928 if (stateZeroSize && !stateNonZeroSize) {
929 stateZeroSize = stateZeroSize->BindExpr(CE, LCtx, destVal);
930 C.addTransition(stateZeroSize);
934 // If the size can be nonzero, we have to check the other arguments.
935 if (stateNonZeroSize) {
936 state = stateNonZeroSize;
938 // Ensure the destination is not null. If it is NULL there will be a
939 // NULL pointer dereference.
940 state = checkNonNull(C, state, Dest, destVal);
944 // Get the value of the Src.
945 SVal srcVal = state->getSVal(Source, LCtx);
947 // Ensure the source is not null. If it is NULL there will be a
948 // NULL pointer dereference.
949 state = checkNonNull(C, state, Source, srcVal);
953 // Ensure the accesses are valid and that the buffers do not overlap.
954 const char * const writeWarning =
955 "Memory copy function overflows destination buffer";
956 state = CheckBufferAccess(C, state, Size, Dest, Source,
957 writeWarning, /* sourceWarning = */ nullptr);
959 state = CheckOverlap(C, state, Size, Dest, Source);
964 // If this is mempcpy, get the byte after the last byte copied and
967 loc::MemRegionVal destRegVal = destVal.castAs<loc::MemRegionVal>();
969 // Get the length to copy.
970 if (Optional<NonLoc> lenValNonLoc = sizeVal.getAs<NonLoc>()) {
971 // Get the byte after the last byte copied.
972 SVal lastElement = C.getSValBuilder().evalBinOpLN(state, BO_Add,
977 // The byte after the last byte copied is the return value.
978 state = state->BindExpr(CE, LCtx, lastElement);
980 // If we don't know how much we copied, we can at least
981 // conjure a return value for later.
982 SVal result = C.getSValBuilder().conjureSymbolVal(nullptr, CE, LCtx,
984 state = state->BindExpr(CE, LCtx, result);
988 // All other copies return the destination buffer.
989 // (Well, bcopy() has a void return type, but this won't hurt.)
990 state = state->BindExpr(CE, LCtx, destVal);
993 // Invalidate the destination (regular invalidation without pointer-escaping
994 // the address of the top-level region).
995 // FIXME: Even if we can't perfectly model the copy, we should see if we
996 // can use LazyCompoundVals to copy the source values into the destination.
997 // This would probably remove any existing bindings past the end of the
998 // copied region, but that's still an improvement over blank invalidation.
999 state = InvalidateBuffer(C, state, Dest, C.getSVal(Dest),
1000 /*IsSourceBuffer*/false);
1002 // Invalidate the source (const-invalidation without const-pointer-escaping
1003 // the address of the top-level region).
1004 state = InvalidateBuffer(C, state, Source, C.getSVal(Source),
1005 /*IsSourceBuffer*/true);
1007 C.addTransition(state);
1012 void CStringChecker::evalMemcpy(CheckerContext &C, const CallExpr *CE) const {
1013 if (CE->getNumArgs() < 3)
1016 // void *memcpy(void *restrict dst, const void *restrict src, size_t n);
1017 // The return value is the address of the destination buffer.
1018 const Expr *Dest = CE->getArg(0);
1019 ProgramStateRef state = C.getState();
1021 evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1), true);
1024 void CStringChecker::evalMempcpy(CheckerContext &C, const CallExpr *CE) const {
1025 if (CE->getNumArgs() < 3)
1028 // void *mempcpy(void *restrict dst, const void *restrict src, size_t n);
1029 // The return value is a pointer to the byte following the last written byte.
1030 const Expr *Dest = CE->getArg(0);
1031 ProgramStateRef state = C.getState();
1033 evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1), true, true);
1036 void CStringChecker::evalMemmove(CheckerContext &C, const CallExpr *CE) const {
1037 if (CE->getNumArgs() < 3)
1040 // void *memmove(void *dst, const void *src, size_t n);
1041 // The return value is the address of the destination buffer.
1042 const Expr *Dest = CE->getArg(0);
1043 ProgramStateRef state = C.getState();
1045 evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1));
1048 void CStringChecker::evalBcopy(CheckerContext &C, const CallExpr *CE) const {
1049 if (CE->getNumArgs() < 3)
1052 // void bcopy(const void *src, void *dst, size_t n);
1053 evalCopyCommon(C, CE, C.getState(),
1054 CE->getArg(2), CE->getArg(1), CE->getArg(0));
1057 void CStringChecker::evalMemcmp(CheckerContext &C, const CallExpr *CE) const {
1058 if (CE->getNumArgs() < 3)
1061 // int memcmp(const void *s1, const void *s2, size_t n);
1062 CurrentFunctionDescription = "memory comparison function";
1064 const Expr *Left = CE->getArg(0);
1065 const Expr *Right = CE->getArg(1);
1066 const Expr *Size = CE->getArg(2);
1068 ProgramStateRef state = C.getState();
1069 SValBuilder &svalBuilder = C.getSValBuilder();
1071 // See if the size argument is zero.
1072 const LocationContext *LCtx = C.getLocationContext();
1073 SVal sizeVal = state->getSVal(Size, LCtx);
1074 QualType sizeTy = Size->getType();
1076 ProgramStateRef stateZeroSize, stateNonZeroSize;
1077 std::tie(stateZeroSize, stateNonZeroSize) =
1078 assumeZero(C, state, sizeVal, sizeTy);
1080 // If the size can be zero, the result will be 0 in that case, and we don't
1081 // have to check either of the buffers.
1082 if (stateZeroSize) {
1083 state = stateZeroSize;
1084 state = state->BindExpr(CE, LCtx,
1085 svalBuilder.makeZeroVal(CE->getType()));
1086 C.addTransition(state);
1089 // If the size can be nonzero, we have to check the other arguments.
1090 if (stateNonZeroSize) {
1091 state = stateNonZeroSize;
1092 // If we know the two buffers are the same, we know the result is 0.
1093 // First, get the two buffers' addresses. Another checker will have already
1094 // made sure they're not undefined.
1095 DefinedOrUnknownSVal LV =
1096 state->getSVal(Left, LCtx).castAs<DefinedOrUnknownSVal>();
1097 DefinedOrUnknownSVal RV =
1098 state->getSVal(Right, LCtx).castAs<DefinedOrUnknownSVal>();
1100 // See if they are the same.
1101 DefinedOrUnknownSVal SameBuf = svalBuilder.evalEQ(state, LV, RV);
1102 ProgramStateRef StSameBuf, StNotSameBuf;
1103 std::tie(StSameBuf, StNotSameBuf) = state->assume(SameBuf);
1105 // If the two arguments might be the same buffer, we know the result is 0,
1106 // and we only need to check one size.
1109 state = CheckBufferAccess(C, state, Size, Left);
1111 state = StSameBuf->BindExpr(CE, LCtx,
1112 svalBuilder.makeZeroVal(CE->getType()));
1113 C.addTransition(state);
1117 // If the two arguments might be different buffers, we have to check the
1118 // size of both of them.
1120 state = StNotSameBuf;
1121 state = CheckBufferAccess(C, state, Size, Left, Right);
1123 // The return value is the comparison result, which we don't know.
1124 SVal CmpV = svalBuilder.conjureSymbolVal(nullptr, CE, LCtx,
1126 state = state->BindExpr(CE, LCtx, CmpV);
1127 C.addTransition(state);
1133 void CStringChecker::evalstrLength(CheckerContext &C,
1134 const CallExpr *CE) const {
1135 if (CE->getNumArgs() < 1)
1138 // size_t strlen(const char *s);
1139 evalstrLengthCommon(C, CE, /* IsStrnlen = */ false);
1142 void CStringChecker::evalstrnLength(CheckerContext &C,
1143 const CallExpr *CE) const {
1144 if (CE->getNumArgs() < 2)
1147 // size_t strnlen(const char *s, size_t maxlen);
1148 evalstrLengthCommon(C, CE, /* IsStrnlen = */ true);
1151 void CStringChecker::evalstrLengthCommon(CheckerContext &C, const CallExpr *CE,
1152 bool IsStrnlen) const {
1153 CurrentFunctionDescription = "string length function";
1154 ProgramStateRef state = C.getState();
1155 const LocationContext *LCtx = C.getLocationContext();
1158 const Expr *maxlenExpr = CE->getArg(1);
1159 SVal maxlenVal = state->getSVal(maxlenExpr, LCtx);
1161 ProgramStateRef stateZeroSize, stateNonZeroSize;
1162 std::tie(stateZeroSize, stateNonZeroSize) =
1163 assumeZero(C, state, maxlenVal, maxlenExpr->getType());
1165 // If the size can be zero, the result will be 0 in that case, and we don't
1166 // have to check the string itself.
1167 if (stateZeroSize) {
1168 SVal zero = C.getSValBuilder().makeZeroVal(CE->getType());
1169 stateZeroSize = stateZeroSize->BindExpr(CE, LCtx, zero);
1170 C.addTransition(stateZeroSize);
1173 // If the size is GUARANTEED to be zero, we're done!
1174 if (!stateNonZeroSize)
1177 // Otherwise, record the assumption that the size is nonzero.
1178 state = stateNonZeroSize;
1181 // Check that the string argument is non-null.
1182 const Expr *Arg = CE->getArg(0);
1183 SVal ArgVal = state->getSVal(Arg, LCtx);
1185 state = checkNonNull(C, state, Arg, ArgVal);
1190 SVal strLength = getCStringLength(C, state, Arg, ArgVal);
1192 // If the argument isn't a valid C string, there's no valid state to
1194 if (strLength.isUndef())
1197 DefinedOrUnknownSVal result = UnknownVal();
1199 // If the check is for strnlen() then bind the return value to no more than
1200 // the maxlen value.
1202 QualType cmpTy = C.getSValBuilder().getConditionType();
1204 // It's a little unfortunate to be getting this again,
1205 // but it's not that expensive...
1206 const Expr *maxlenExpr = CE->getArg(1);
1207 SVal maxlenVal = state->getSVal(maxlenExpr, LCtx);
1209 Optional<NonLoc> strLengthNL = strLength.getAs<NonLoc>();
1210 Optional<NonLoc> maxlenValNL = maxlenVal.getAs<NonLoc>();
1212 if (strLengthNL && maxlenValNL) {
1213 ProgramStateRef stateStringTooLong, stateStringNotTooLong;
1215 // Check if the strLength is greater than the maxlen.
1216 std::tie(stateStringTooLong, stateStringNotTooLong) = state->assume(
1218 .evalBinOpNN(state, BO_GT, *strLengthNL, *maxlenValNL, cmpTy)
1219 .castAs<DefinedOrUnknownSVal>());
1221 if (stateStringTooLong && !stateStringNotTooLong) {
1222 // If the string is longer than maxlen, return maxlen.
1223 result = *maxlenValNL;
1224 } else if (stateStringNotTooLong && !stateStringTooLong) {
1225 // If the string is shorter than maxlen, return its length.
1226 result = *strLengthNL;
1230 if (result.isUnknown()) {
1231 // If we don't have enough information for a comparison, there's
1232 // no guarantee the full string length will actually be returned.
1233 // All we know is the return value is the min of the string length
1234 // and the limit. This is better than nothing.
1235 result = C.getSValBuilder().conjureSymbolVal(nullptr, CE, LCtx,
1237 NonLoc resultNL = result.castAs<NonLoc>();
1240 state = state->assume(C.getSValBuilder().evalBinOpNN(
1241 state, BO_LE, resultNL, *strLengthNL, cmpTy)
1242 .castAs<DefinedOrUnknownSVal>(), true);
1246 state = state->assume(C.getSValBuilder().evalBinOpNN(
1247 state, BO_LE, resultNL, *maxlenValNL, cmpTy)
1248 .castAs<DefinedOrUnknownSVal>(), true);
1253 // This is a plain strlen(), not strnlen().
1254 result = strLength.castAs<DefinedOrUnknownSVal>();
1256 // If we don't know the length of the string, conjure a return
1257 // value, so it can be used in constraints, at least.
1258 if (result.isUnknown()) {
1259 result = C.getSValBuilder().conjureSymbolVal(nullptr, CE, LCtx,
1264 // Bind the return value.
1265 assert(!result.isUnknown() && "Should have conjured a value by now");
1266 state = state->BindExpr(CE, LCtx, result);
1267 C.addTransition(state);
1270 void CStringChecker::evalStrcpy(CheckerContext &C, const CallExpr *CE) const {
1271 if (CE->getNumArgs() < 2)
1274 // char *strcpy(char *restrict dst, const char *restrict src);
1275 evalStrcpyCommon(C, CE,
1276 /* returnEnd = */ false,
1277 /* isBounded = */ false,
1278 /* isAppending = */ false);
1281 void CStringChecker::evalStrncpy(CheckerContext &C, const CallExpr *CE) const {
1282 if (CE->getNumArgs() < 3)
1285 // char *strncpy(char *restrict dst, const char *restrict src, size_t n);
1286 evalStrcpyCommon(C, CE,
1287 /* returnEnd = */ false,
1288 /* isBounded = */ true,
1289 /* isAppending = */ false);
1292 void CStringChecker::evalStpcpy(CheckerContext &C, const CallExpr *CE) const {
1293 if (CE->getNumArgs() < 2)
1296 // char *stpcpy(char *restrict dst, const char *restrict src);
1297 evalStrcpyCommon(C, CE,
1298 /* returnEnd = */ true,
1299 /* isBounded = */ false,
1300 /* isAppending = */ false);
1303 void CStringChecker::evalStrcat(CheckerContext &C, const CallExpr *CE) const {
1304 if (CE->getNumArgs() < 2)
1307 //char *strcat(char *restrict s1, const char *restrict s2);
1308 evalStrcpyCommon(C, CE,
1309 /* returnEnd = */ false,
1310 /* isBounded = */ false,
1311 /* isAppending = */ true);
1314 void CStringChecker::evalStrncat(CheckerContext &C, const CallExpr *CE) const {
1315 if (CE->getNumArgs() < 3)
1318 //char *strncat(char *restrict s1, const char *restrict s2, size_t n);
1319 evalStrcpyCommon(C, CE,
1320 /* returnEnd = */ false,
1321 /* isBounded = */ true,
1322 /* isAppending = */ true);
1325 void CStringChecker::evalStrcpyCommon(CheckerContext &C, const CallExpr *CE,
1326 bool returnEnd, bool isBounded,
1327 bool isAppending) const {
1328 CurrentFunctionDescription = "string copy function";
1329 ProgramStateRef state = C.getState();
1330 const LocationContext *LCtx = C.getLocationContext();
1332 // Check that the destination is non-null.
1333 const Expr *Dst = CE->getArg(0);
1334 SVal DstVal = state->getSVal(Dst, LCtx);
1336 state = checkNonNull(C, state, Dst, DstVal);
1340 // Check that the source is non-null.
1341 const Expr *srcExpr = CE->getArg(1);
1342 SVal srcVal = state->getSVal(srcExpr, LCtx);
1343 state = checkNonNull(C, state, srcExpr, srcVal);
1347 // Get the string length of the source.
1348 SVal strLength = getCStringLength(C, state, srcExpr, srcVal);
1350 // If the source isn't a valid C string, give up.
1351 if (strLength.isUndef())
1354 SValBuilder &svalBuilder = C.getSValBuilder();
1355 QualType cmpTy = svalBuilder.getConditionType();
1356 QualType sizeTy = svalBuilder.getContext().getSizeType();
1358 // These two values allow checking two kinds of errors:
1359 // - actual overflows caused by a source that doesn't fit in the destination
1360 // - potential overflows caused by a bound that could exceed the destination
1361 SVal amountCopied = UnknownVal();
1362 SVal maxLastElementIndex = UnknownVal();
1363 const char *boundWarning = nullptr;
1365 // If the function is strncpy, strncat, etc... it is bounded.
1367 // Get the max number of characters to copy.
1368 const Expr *lenExpr = CE->getArg(2);
1369 SVal lenVal = state->getSVal(lenExpr, LCtx);
1371 // Protect against misdeclared strncpy().
1372 lenVal = svalBuilder.evalCast(lenVal, sizeTy, lenExpr->getType());
1374 Optional<NonLoc> strLengthNL = strLength.getAs<NonLoc>();
1375 Optional<NonLoc> lenValNL = lenVal.getAs<NonLoc>();
1377 // If we know both values, we might be able to figure out how much
1379 if (strLengthNL && lenValNL) {
1380 ProgramStateRef stateSourceTooLong, stateSourceNotTooLong;
1382 // Check if the max number to copy is less than the length of the src.
1383 // If the bound is equal to the source length, strncpy won't null-
1384 // terminate the result!
1385 std::tie(stateSourceTooLong, stateSourceNotTooLong) = state->assume(
1386 svalBuilder.evalBinOpNN(state, BO_GE, *strLengthNL, *lenValNL, cmpTy)
1387 .castAs<DefinedOrUnknownSVal>());
1389 if (stateSourceTooLong && !stateSourceNotTooLong) {
1390 // Max number to copy is less than the length of the src, so the actual
1391 // strLength copied is the max number arg.
1392 state = stateSourceTooLong;
1393 amountCopied = lenVal;
1395 } else if (!stateSourceTooLong && stateSourceNotTooLong) {
1396 // The source buffer entirely fits in the bound.
1397 state = stateSourceNotTooLong;
1398 amountCopied = strLength;
1402 // We still want to know if the bound is known to be too large.
1405 // For strncat, the check is strlen(dst) + lenVal < sizeof(dst)
1407 // Get the string length of the destination. If the destination is
1408 // memory that can't have a string length, we shouldn't be copying
1410 SVal dstStrLength = getCStringLength(C, state, Dst, DstVal);
1411 if (dstStrLength.isUndef())
1414 if (Optional<NonLoc> dstStrLengthNL = dstStrLength.getAs<NonLoc>()) {
1415 maxLastElementIndex = svalBuilder.evalBinOpNN(state, BO_Add,
1419 boundWarning = "Size argument is greater than the free space in the "
1420 "destination buffer";
1424 // For strncpy, this is just checking that lenVal <= sizeof(dst)
1425 // (Yes, strncpy and strncat differ in how they treat termination.
1426 // strncat ALWAYS terminates, but strncpy doesn't.)
1428 // We need a special case for when the copy size is zero, in which
1429 // case strncpy will do no work at all. Our bounds check uses n-1
1430 // as the last element accessed, so n == 0 is problematic.
1431 ProgramStateRef StateZeroSize, StateNonZeroSize;
1432 std::tie(StateZeroSize, StateNonZeroSize) =
1433 assumeZero(C, state, *lenValNL, sizeTy);
1435 // If the size is known to be zero, we're done.
1436 if (StateZeroSize && !StateNonZeroSize) {
1437 StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, DstVal);
1438 C.addTransition(StateZeroSize);
1442 // Otherwise, go ahead and figure out the last element we'll touch.
1443 // We don't record the non-zero assumption here because we can't
1444 // be sure. We won't warn on a possible zero.
1445 NonLoc one = svalBuilder.makeIntVal(1, sizeTy).castAs<NonLoc>();
1446 maxLastElementIndex = svalBuilder.evalBinOpNN(state, BO_Sub, *lenValNL,
1448 boundWarning = "Size argument is greater than the length of the "
1449 "destination buffer";
1453 // If we couldn't pin down the copy length, at least bound it.
1454 // FIXME: We should actually run this code path for append as well, but
1455 // right now it creates problems with constraints (since we can end up
1456 // trying to pass constraints from symbol to symbol).
1457 if (amountCopied.isUnknown() && !isAppending) {
1458 // Try to get a "hypothetical" string length symbol, which we can later
1459 // set as a real value if that turns out to be the case.
1460 amountCopied = getCStringLength(C, state, lenExpr, srcVal, true);
1461 assert(!amountCopied.isUndef());
1463 if (Optional<NonLoc> amountCopiedNL = amountCopied.getAs<NonLoc>()) {
1465 // amountCopied <= lenVal
1466 SVal copiedLessThanBound = svalBuilder.evalBinOpNN(state, BO_LE,
1470 state = state->assume(
1471 copiedLessThanBound.castAs<DefinedOrUnknownSVal>(), true);
1477 // amountCopied <= strlen(source)
1478 SVal copiedLessThanSrc = svalBuilder.evalBinOpNN(state, BO_LE,
1482 state = state->assume(
1483 copiedLessThanSrc.castAs<DefinedOrUnknownSVal>(), true);
1491 // The function isn't bounded. The amount copied should match the length
1492 // of the source buffer.
1493 amountCopied = strLength;
1498 // This represents the number of characters copied into the destination
1499 // buffer. (It may not actually be the strlen if the destination buffer
1500 // is not terminated.)
1501 SVal finalStrLength = UnknownVal();
1503 // If this is an appending function (strcat, strncat...) then set the
1504 // string length to strlen(src) + strlen(dst) since the buffer will
1505 // ultimately contain both.
1507 // Get the string length of the destination. If the destination is memory
1508 // that can't have a string length, we shouldn't be copying into it anyway.
1509 SVal dstStrLength = getCStringLength(C, state, Dst, DstVal);
1510 if (dstStrLength.isUndef())
1513 Optional<NonLoc> srcStrLengthNL = amountCopied.getAs<NonLoc>();
1514 Optional<NonLoc> dstStrLengthNL = dstStrLength.getAs<NonLoc>();
1516 // If we know both string lengths, we might know the final string length.
1517 if (srcStrLengthNL && dstStrLengthNL) {
1518 // Make sure the two lengths together don't overflow a size_t.
1519 state = checkAdditionOverflow(C, state, *srcStrLengthNL, *dstStrLengthNL);
1523 finalStrLength = svalBuilder.evalBinOpNN(state, BO_Add, *srcStrLengthNL,
1524 *dstStrLengthNL, sizeTy);
1527 // If we couldn't get a single value for the final string length,
1528 // we can at least bound it by the individual lengths.
1529 if (finalStrLength.isUnknown()) {
1530 // Try to get a "hypothetical" string length symbol, which we can later
1531 // set as a real value if that turns out to be the case.
1532 finalStrLength = getCStringLength(C, state, CE, DstVal, true);
1533 assert(!finalStrLength.isUndef());
1535 if (Optional<NonLoc> finalStrLengthNL = finalStrLength.getAs<NonLoc>()) {
1536 if (srcStrLengthNL) {
1537 // finalStrLength >= srcStrLength
1538 SVal sourceInResult = svalBuilder.evalBinOpNN(state, BO_GE,
1542 state = state->assume(sourceInResult.castAs<DefinedOrUnknownSVal>(),
1548 if (dstStrLengthNL) {
1549 // finalStrLength >= dstStrLength
1550 SVal destInResult = svalBuilder.evalBinOpNN(state, BO_GE,
1555 state->assume(destInResult.castAs<DefinedOrUnknownSVal>(), true);
1563 // Otherwise, this is a copy-over function (strcpy, strncpy, ...), and
1564 // the final string length will match the input string length.
1565 finalStrLength = amountCopied;
1568 // The final result of the function will either be a pointer past the last
1569 // copied element, or a pointer to the start of the destination buffer.
1570 SVal Result = (returnEnd ? UnknownVal() : DstVal);
1574 // If the destination is a MemRegion, try to check for a buffer overflow and
1575 // record the new string length.
1576 if (Optional<loc::MemRegionVal> dstRegVal =
1577 DstVal.getAs<loc::MemRegionVal>()) {
1578 QualType ptrTy = Dst->getType();
1580 // If we have an exact value on a bounded copy, use that to check for
1581 // overflows, rather than our estimate about how much is actually copied.
1583 if (Optional<NonLoc> maxLastNL = maxLastElementIndex.getAs<NonLoc>()) {
1584 SVal maxLastElement = svalBuilder.evalBinOpLN(state, BO_Add, *dstRegVal,
1586 state = CheckLocation(C, state, CE->getArg(2), maxLastElement,
1593 // Then, if the final length is known...
1594 if (Optional<NonLoc> knownStrLength = finalStrLength.getAs<NonLoc>()) {
1595 SVal lastElement = svalBuilder.evalBinOpLN(state, BO_Add, *dstRegVal,
1596 *knownStrLength, ptrTy);
1598 // ...and we haven't checked the bound, we'll check the actual copy.
1599 if (!boundWarning) {
1600 const char * const warningMsg =
1601 "String copy function overflows destination buffer";
1602 state = CheckLocation(C, state, Dst, lastElement, warningMsg);
1607 // If this is a stpcpy-style copy, the last element is the return value.
1609 Result = lastElement;
1612 // Invalidate the destination (regular invalidation without pointer-escaping
1613 // the address of the top-level region). This must happen before we set the
1614 // C string length because invalidation will clear the length.
1615 // FIXME: Even if we can't perfectly model the copy, we should see if we
1616 // can use LazyCompoundVals to copy the source values into the destination.
1617 // This would probably remove any existing bindings past the end of the
1618 // string, but that's still an improvement over blank invalidation.
1619 state = InvalidateBuffer(C, state, Dst, *dstRegVal,
1620 /*IsSourceBuffer*/false);
1622 // Invalidate the source (const-invalidation without const-pointer-escaping
1623 // the address of the top-level region).
1624 state = InvalidateBuffer(C, state, srcExpr, srcVal, /*IsSourceBuffer*/true);
1626 // Set the C string length of the destination, if we know it.
1627 if (isBounded && !isAppending) {
1628 // strncpy is annoying in that it doesn't guarantee to null-terminate
1629 // the result string. If the original string didn't fit entirely inside
1630 // the bound (including the null-terminator), we don't know how long the
1632 if (amountCopied != strLength)
1633 finalStrLength = UnknownVal();
1635 state = setCStringLength(state, dstRegVal->getRegion(), finalStrLength);
1640 // If this is a stpcpy-style copy, but we were unable to check for a buffer
1641 // overflow, we still need a result. Conjure a return value.
1642 if (returnEnd && Result.isUnknown()) {
1643 Result = svalBuilder.conjureSymbolVal(nullptr, CE, LCtx, C.blockCount());
1646 // Set the return value.
1647 state = state->BindExpr(CE, LCtx, Result);
1648 C.addTransition(state);
1651 void CStringChecker::evalStrcmp(CheckerContext &C, const CallExpr *CE) const {
1652 if (CE->getNumArgs() < 2)
1655 //int strcmp(const char *s1, const char *s2);
1656 evalStrcmpCommon(C, CE, /* isBounded = */ false, /* ignoreCase = */ false);
1659 void CStringChecker::evalStrncmp(CheckerContext &C, const CallExpr *CE) const {
1660 if (CE->getNumArgs() < 3)
1663 //int strncmp(const char *s1, const char *s2, size_t n);
1664 evalStrcmpCommon(C, CE, /* isBounded = */ true, /* ignoreCase = */ false);
1667 void CStringChecker::evalStrcasecmp(CheckerContext &C,
1668 const CallExpr *CE) const {
1669 if (CE->getNumArgs() < 2)
1672 //int strcasecmp(const char *s1, const char *s2);
1673 evalStrcmpCommon(C, CE, /* isBounded = */ false, /* ignoreCase = */ true);
1676 void CStringChecker::evalStrncasecmp(CheckerContext &C,
1677 const CallExpr *CE) const {
1678 if (CE->getNumArgs() < 3)
1681 //int strncasecmp(const char *s1, const char *s2, size_t n);
1682 evalStrcmpCommon(C, CE, /* isBounded = */ true, /* ignoreCase = */ true);
1685 void CStringChecker::evalStrcmpCommon(CheckerContext &C, const CallExpr *CE,
1686 bool isBounded, bool ignoreCase) const {
1687 CurrentFunctionDescription = "string comparison function";
1688 ProgramStateRef state = C.getState();
1689 const LocationContext *LCtx = C.getLocationContext();
1691 // Check that the first string is non-null
1692 const Expr *s1 = CE->getArg(0);
1693 SVal s1Val = state->getSVal(s1, LCtx);
1694 state = checkNonNull(C, state, s1, s1Val);
1698 // Check that the second string is non-null.
1699 const Expr *s2 = CE->getArg(1);
1700 SVal s2Val = state->getSVal(s2, LCtx);
1701 state = checkNonNull(C, state, s2, s2Val);
1705 // Get the string length of the first string or give up.
1706 SVal s1Length = getCStringLength(C, state, s1, s1Val);
1707 if (s1Length.isUndef())
1710 // Get the string length of the second string or give up.
1711 SVal s2Length = getCStringLength(C, state, s2, s2Val);
1712 if (s2Length.isUndef())
1715 // If we know the two buffers are the same, we know the result is 0.
1716 // First, get the two buffers' addresses. Another checker will have already
1717 // made sure they're not undefined.
1718 DefinedOrUnknownSVal LV = s1Val.castAs<DefinedOrUnknownSVal>();
1719 DefinedOrUnknownSVal RV = s2Val.castAs<DefinedOrUnknownSVal>();
1721 // See if they are the same.
1722 SValBuilder &svalBuilder = C.getSValBuilder();
1723 DefinedOrUnknownSVal SameBuf = svalBuilder.evalEQ(state, LV, RV);
1724 ProgramStateRef StSameBuf, StNotSameBuf;
1725 std::tie(StSameBuf, StNotSameBuf) = state->assume(SameBuf);
1727 // If the two arguments might be the same buffer, we know the result is 0,
1728 // and we only need to check one size.
1730 StSameBuf = StSameBuf->BindExpr(CE, LCtx,
1731 svalBuilder.makeZeroVal(CE->getType()));
1732 C.addTransition(StSameBuf);
1734 // If the two arguments are GUARANTEED to be the same, we're done!
1739 assert(StNotSameBuf);
1740 state = StNotSameBuf;
1742 // At this point we can go about comparing the two buffers.
1743 // For now, we only do this if they're both known string literals.
1745 // Attempt to extract string literals from both expressions.
1746 const StringLiteral *s1StrLiteral = getCStringLiteral(C, state, s1, s1Val);
1747 const StringLiteral *s2StrLiteral = getCStringLiteral(C, state, s2, s2Val);
1748 bool canComputeResult = false;
1750 if (s1StrLiteral && s2StrLiteral) {
1751 StringRef s1StrRef = s1StrLiteral->getString();
1752 StringRef s2StrRef = s2StrLiteral->getString();
1755 // Get the max number of characters to compare.
1756 const Expr *lenExpr = CE->getArg(2);
1757 SVal lenVal = state->getSVal(lenExpr, LCtx);
1759 // If the length is known, we can get the right substrings.
1760 if (const llvm::APSInt *len = svalBuilder.getKnownValue(state, lenVal)) {
1761 // Create substrings of each to compare the prefix.
1762 s1StrRef = s1StrRef.substr(0, (size_t)len->getZExtValue());
1763 s2StrRef = s2StrRef.substr(0, (size_t)len->getZExtValue());
1764 canComputeResult = true;
1767 // This is a normal, unbounded strcmp.
1768 canComputeResult = true;
1771 if (canComputeResult) {
1772 // Real strcmp stops at null characters.
1773 size_t s1Term = s1StrRef.find('\0');
1774 if (s1Term != StringRef::npos)
1775 s1StrRef = s1StrRef.substr(0, s1Term);
1777 size_t s2Term = s2StrRef.find('\0');
1778 if (s2Term != StringRef::npos)
1779 s2StrRef = s2StrRef.substr(0, s2Term);
1781 // Use StringRef's comparison methods to compute the actual result.
1785 // Compare string 1 to string 2 the same way strcasecmp() does.
1786 result = s1StrRef.compare_lower(s2StrRef);
1788 // Compare string 1 to string 2 the same way strcmp() does.
1789 result = s1StrRef.compare(s2StrRef);
1792 // Build the SVal of the comparison and bind the return value.
1793 SVal resultVal = svalBuilder.makeIntVal(result, CE->getType());
1794 state = state->BindExpr(CE, LCtx, resultVal);
1798 if (!canComputeResult) {
1799 // Conjure a symbolic value. It's the best we can do.
1800 SVal resultVal = svalBuilder.conjureSymbolVal(nullptr, CE, LCtx,
1802 state = state->BindExpr(CE, LCtx, resultVal);
1805 // Record this as a possible path.
1806 C.addTransition(state);
1809 void CStringChecker::evalStrsep(CheckerContext &C, const CallExpr *CE) const {
1810 //char *strsep(char **stringp, const char *delim);
1811 if (CE->getNumArgs() < 2)
1814 // Sanity: does the search string parameter match the return type?
1815 const Expr *SearchStrPtr = CE->getArg(0);
1816 QualType CharPtrTy = SearchStrPtr->getType()->getPointeeType();
1817 if (CharPtrTy.isNull() ||
1818 CE->getType().getUnqualifiedType() != CharPtrTy.getUnqualifiedType())
1821 CurrentFunctionDescription = "strsep()";
1822 ProgramStateRef State = C.getState();
1823 const LocationContext *LCtx = C.getLocationContext();
1825 // Check that the search string pointer is non-null (though it may point to
1827 SVal SearchStrVal = State->getSVal(SearchStrPtr, LCtx);
1828 State = checkNonNull(C, State, SearchStrPtr, SearchStrVal);
1832 // Check that the delimiter string is non-null.
1833 const Expr *DelimStr = CE->getArg(1);
1834 SVal DelimStrVal = State->getSVal(DelimStr, LCtx);
1835 State = checkNonNull(C, State, DelimStr, DelimStrVal);
1839 SValBuilder &SVB = C.getSValBuilder();
1841 if (Optional<Loc> SearchStrLoc = SearchStrVal.getAs<Loc>()) {
1842 // Get the current value of the search string pointer, as a char*.
1843 Result = State->getSVal(*SearchStrLoc, CharPtrTy);
1845 // Invalidate the search string, representing the change of one delimiter
1846 // character to NUL.
1847 State = InvalidateBuffer(C, State, SearchStrPtr, Result,
1848 /*IsSourceBuffer*/false);
1850 // Overwrite the search string pointer. The new value is either an address
1851 // further along in the same string, or NULL if there are no more tokens.
1852 State = State->bindLoc(*SearchStrLoc,
1853 SVB.conjureSymbolVal(getTag(), CE, LCtx, CharPtrTy,
1856 assert(SearchStrVal.isUnknown());
1857 // Conjure a symbolic value. It's the best we can do.
1858 Result = SVB.conjureSymbolVal(nullptr, CE, LCtx, C.blockCount());
1861 // Set the return value, and finish.
1862 State = State->BindExpr(CE, LCtx, Result);
1863 C.addTransition(State);
1867 //===----------------------------------------------------------------------===//
1868 // The driver method, and other Checker callbacks.
1869 //===----------------------------------------------------------------------===//
1871 bool CStringChecker::evalCall(const CallExpr *CE, CheckerContext &C) const {
1872 const FunctionDecl *FDecl = C.getCalleeDecl(CE);
1877 // FIXME: Poorly-factored string switches are slow.
1878 FnCheck evalFunction = nullptr;
1879 if (C.isCLibraryFunction(FDecl, "memcpy"))
1880 evalFunction = &CStringChecker::evalMemcpy;
1881 else if (C.isCLibraryFunction(FDecl, "mempcpy"))
1882 evalFunction = &CStringChecker::evalMempcpy;
1883 else if (C.isCLibraryFunction(FDecl, "memcmp"))
1884 evalFunction = &CStringChecker::evalMemcmp;
1885 else if (C.isCLibraryFunction(FDecl, "memmove"))
1886 evalFunction = &CStringChecker::evalMemmove;
1887 else if (C.isCLibraryFunction(FDecl, "strcpy"))
1888 evalFunction = &CStringChecker::evalStrcpy;
1889 else if (C.isCLibraryFunction(FDecl, "strncpy"))
1890 evalFunction = &CStringChecker::evalStrncpy;
1891 else if (C.isCLibraryFunction(FDecl, "stpcpy"))
1892 evalFunction = &CStringChecker::evalStpcpy;
1893 else if (C.isCLibraryFunction(FDecl, "strcat"))
1894 evalFunction = &CStringChecker::evalStrcat;
1895 else if (C.isCLibraryFunction(FDecl, "strncat"))
1896 evalFunction = &CStringChecker::evalStrncat;
1897 else if (C.isCLibraryFunction(FDecl, "strlen"))
1898 evalFunction = &CStringChecker::evalstrLength;
1899 else if (C.isCLibraryFunction(FDecl, "strnlen"))
1900 evalFunction = &CStringChecker::evalstrnLength;
1901 else if (C.isCLibraryFunction(FDecl, "strcmp"))
1902 evalFunction = &CStringChecker::evalStrcmp;
1903 else if (C.isCLibraryFunction(FDecl, "strncmp"))
1904 evalFunction = &CStringChecker::evalStrncmp;
1905 else if (C.isCLibraryFunction(FDecl, "strcasecmp"))
1906 evalFunction = &CStringChecker::evalStrcasecmp;
1907 else if (C.isCLibraryFunction(FDecl, "strncasecmp"))
1908 evalFunction = &CStringChecker::evalStrncasecmp;
1909 else if (C.isCLibraryFunction(FDecl, "strsep"))
1910 evalFunction = &CStringChecker::evalStrsep;
1911 else if (C.isCLibraryFunction(FDecl, "bcopy"))
1912 evalFunction = &CStringChecker::evalBcopy;
1913 else if (C.isCLibraryFunction(FDecl, "bcmp"))
1914 evalFunction = &CStringChecker::evalMemcmp;
1916 // If the callee isn't a string function, let another checker handle it.
1920 // Make sure each function sets its own description.
1921 // (But don't bother in a release build.)
1922 assert(!(CurrentFunctionDescription = nullptr));
1924 // Check and evaluate the call.
1925 (this->*evalFunction)(C, CE);
1927 // If the evaluate call resulted in no change, chain to the next eval call
1929 // Note, the custom CString evaluation calls assume that basic safety
1930 // properties are held. However, if the user chooses to turn off some of these
1931 // checks, we ignore the issues and leave the call evaluation to a generic
1933 if (!C.isDifferent())
1939 void CStringChecker::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const {
1940 // Record string length for char a[] = "abc";
1941 ProgramStateRef state = C.getState();
1943 for (const auto *I : DS->decls()) {
1944 const VarDecl *D = dyn_cast<VarDecl>(I);
1948 // FIXME: Handle array fields of structs.
1949 if (!D->getType()->isArrayType())
1952 const Expr *Init = D->getInit();
1955 if (!isa<StringLiteral>(Init))
1958 Loc VarLoc = state->getLValue(D, C.getLocationContext());
1959 const MemRegion *MR = VarLoc.getAsRegion();
1963 SVal StrVal = state->getSVal(Init, C.getLocationContext());
1964 assert(StrVal.isValid() && "Initializer string is unknown or undefined");
1965 DefinedOrUnknownSVal strLength =
1966 getCStringLength(C, state, Init, StrVal).castAs<DefinedOrUnknownSVal>();
1968 state = state->set<CStringLength>(MR, strLength);
1971 C.addTransition(state);
1974 bool CStringChecker::wantsRegionChangeUpdate(ProgramStateRef state) const {
1975 CStringLengthTy Entries = state->get<CStringLength>();
1976 return !Entries.isEmpty();
1980 CStringChecker::checkRegionChanges(ProgramStateRef state,
1981 const InvalidatedSymbols *,
1982 ArrayRef<const MemRegion *> ExplicitRegions,
1983 ArrayRef<const MemRegion *> Regions,
1984 const CallEvent *Call) const {
1985 CStringLengthTy Entries = state->get<CStringLength>();
1986 if (Entries.isEmpty())
1989 llvm::SmallPtrSet<const MemRegion *, 8> Invalidated;
1990 llvm::SmallPtrSet<const MemRegion *, 32> SuperRegions;
1992 // First build sets for the changed regions and their super-regions.
1993 for (ArrayRef<const MemRegion *>::iterator
1994 I = Regions.begin(), E = Regions.end(); I != E; ++I) {
1995 const MemRegion *MR = *I;
1996 Invalidated.insert(MR);
1998 SuperRegions.insert(MR);
1999 while (const SubRegion *SR = dyn_cast<SubRegion>(MR)) {
2000 MR = SR->getSuperRegion();
2001 SuperRegions.insert(MR);
2005 CStringLengthTy::Factory &F = state->get_context<CStringLength>();
2007 // Then loop over the entries in the current state.
2008 for (CStringLengthTy::iterator I = Entries.begin(),
2009 E = Entries.end(); I != E; ++I) {
2010 const MemRegion *MR = I.getKey();
2012 // Is this entry for a super-region of a changed region?
2013 if (SuperRegions.count(MR)) {
2014 Entries = F.remove(Entries, MR);
2018 // Is this entry for a sub-region of a changed region?
2019 const MemRegion *Super = MR;
2020 while (const SubRegion *SR = dyn_cast<SubRegion>(Super)) {
2021 Super = SR->getSuperRegion();
2022 if (Invalidated.count(Super)) {
2023 Entries = F.remove(Entries, MR);
2029 return state->set<CStringLength>(Entries);
2032 void CStringChecker::checkLiveSymbols(ProgramStateRef state,
2033 SymbolReaper &SR) const {
2034 // Mark all symbols in our string length map as valid.
2035 CStringLengthTy Entries = state->get<CStringLength>();
2037 for (CStringLengthTy::iterator I = Entries.begin(), E = Entries.end();
2039 SVal Len = I.getData();
2041 for (SymExpr::symbol_iterator si = Len.symbol_begin(),
2042 se = Len.symbol_end(); si != se; ++si)
2047 void CStringChecker::checkDeadSymbols(SymbolReaper &SR,
2048 CheckerContext &C) const {
2049 if (!SR.hasDeadSymbols())
2052 ProgramStateRef state = C.getState();
2053 CStringLengthTy Entries = state->get<CStringLength>();
2054 if (Entries.isEmpty())
2057 CStringLengthTy::Factory &F = state->get_context<CStringLength>();
2058 for (CStringLengthTy::iterator I = Entries.begin(), E = Entries.end();
2060 SVal Len = I.getData();
2061 if (SymbolRef Sym = Len.getAsSymbol()) {
2063 Entries = F.remove(Entries, I.getKey());
2067 state = state->set<CStringLength>(Entries);
2068 C.addTransition(state);
2071 #define REGISTER_CHECKER(name) \
2072 void ento::register##name(CheckerManager &mgr) { \
2073 CStringChecker *checker = mgr.registerChecker<CStringChecker>(); \
2074 checker->Filter.Check##name = true; \
2075 checker->Filter.CheckName##name = mgr.getCurrentCheckName(); \
2078 REGISTER_CHECKER(CStringNullArg)
2079 REGISTER_CHECKER(CStringOutOfBounds)
2080 REGISTER_CHECKER(CStringBufferOverlap)
2081 REGISTER_CHECKER(CStringNotNullTerm)
2083 void ento::registerCStringCheckerBasic(CheckerManager &Mgr) {
2084 registerCStringNullArg(Mgr);