| //= CStringChecker.h - Checks calls to C string functions ----------*- C++ -*-// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This defines CStringChecker, which is an assortment of checks on calls |
| // to functions in <string.h>. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "ClangSACheckers.h" |
| #include "clang/StaticAnalyzer/Core/Checker.h" |
| #include "clang/StaticAnalyzer/Core/CheckerManager.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" |
| #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/GRStateTrait.h" |
| #include "llvm/ADT/StringSwitch.h" |
| |
| using namespace clang; |
| using namespace ento; |
| |
| namespace { |
| class CStringChecker : public Checker< eval::Call, |
| check::PreStmt<DeclStmt>, |
| check::LiveSymbols, |
| check::DeadSymbols, |
| check::RegionChanges |
| > { |
| mutable llvm::OwningPtr<BugType> BT_Null, BT_Bounds, |
| BT_Overlap, BT_NotCString, |
| BT_AdditionOverflow; |
| mutable const char *CurrentFunctionDescription; |
| |
| public: |
| static void *getTag() { static int tag; return &tag; } |
| |
| bool evalCall(const CallExpr *CE, CheckerContext &C) const; |
| void checkPreStmt(const DeclStmt *DS, CheckerContext &C) const; |
| void checkLiveSymbols(const GRState *state, SymbolReaper &SR) const; |
| void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const; |
| bool wantsRegionChangeUpdate(const GRState *state) const; |
| |
| const GRState *checkRegionChanges(const GRState *state, |
| const StoreManager::InvalidatedSymbols *, |
| const MemRegion * const *Begin, |
| const MemRegion * const *End) const; |
| |
| typedef void (CStringChecker::*FnCheck)(CheckerContext &, |
| const CallExpr *) const; |
| |
| void evalMemcpy(CheckerContext &C, const CallExpr *CE) const; |
| void evalMempcpy(CheckerContext &C, const CallExpr *CE) const; |
| void evalMemmove(CheckerContext &C, const CallExpr *CE) const; |
| void evalBcopy(CheckerContext &C, const CallExpr *CE) const; |
| void evalCopyCommon(CheckerContext &C, const CallExpr *CE, |
| const GRState *state, |
| const Expr *Size, const Expr *Source, const Expr *Dest, |
| bool Restricted = false, |
| bool IsMempcpy = false) const; |
| |
| void evalMemcmp(CheckerContext &C, const CallExpr *CE) const; |
| |
| void evalstrLength(CheckerContext &C, const CallExpr *CE) const; |
| void evalstrnLength(CheckerContext &C, const CallExpr *CE) const; |
| void evalstrLengthCommon(CheckerContext &C, const CallExpr *CE, |
| bool IsStrnlen = false) const; |
| |
| void evalStrcpy(CheckerContext &C, const CallExpr *CE) const; |
| void evalStrncpy(CheckerContext &C, const CallExpr *CE) const; |
| void evalStpcpy(CheckerContext &C, const CallExpr *CE) const; |
| void evalStrcpyCommon(CheckerContext &C, const CallExpr *CE, bool returnEnd, |
| bool isBounded, bool isAppending) const; |
| |
| void evalStrcat(CheckerContext &C, const CallExpr *CE) const; |
| void evalStrncat(CheckerContext &C, const CallExpr *CE) const; |
| |
| void evalStrcmp(CheckerContext &C, const CallExpr *CE) const; |
| void evalStrncmp(CheckerContext &C, const CallExpr *CE) const; |
| void evalStrcasecmp(CheckerContext &C, const CallExpr *CE) const; |
| void evalStrncasecmp(CheckerContext &C, const CallExpr *CE) const; |
| void evalStrcmpCommon(CheckerContext &C, const CallExpr *CE, |
| bool isBounded = false, bool ignoreCase = false) const; |
| |
| // Utility methods |
| std::pair<const GRState*, const GRState*> |
| static assumeZero(CheckerContext &C, |
| const GRState *state, SVal V, QualType Ty); |
| |
| static const GRState *setCStringLength(const GRState *state, |
| const MemRegion *MR, SVal strLength); |
| static SVal getCStringLengthForRegion(CheckerContext &C, |
| const GRState *&state, |
| const Expr *Ex, const MemRegion *MR, |
| bool hypothetical); |
| SVal getCStringLength(CheckerContext &C, const GRState *&state, |
| const Expr *Ex, SVal Buf, |
| bool hypothetical = false) const; |
| |
| const StringLiteral *getCStringLiteral(CheckerContext &C, |
| const GRState *&state, |
| const Expr *expr, |
| SVal val) const; |
| |
| static const GRState *InvalidateBuffer(CheckerContext &C, |
| const GRState *state, |
| const Expr *Ex, SVal V); |
| |
| static bool SummarizeRegion(raw_ostream &os, ASTContext &Ctx, |
| const MemRegion *MR); |
| |
| // Re-usable checks |
| const GRState *checkNonNull(CheckerContext &C, const GRState *state, |
| const Expr *S, SVal l) const; |
| const GRState *CheckLocation(CheckerContext &C, const GRState *state, |
| const Expr *S, SVal l, |
| const char *message = NULL) const; |
| const GRState *CheckBufferAccess(CheckerContext &C, const GRState *state, |
| const Expr *Size, |
| const Expr *FirstBuf, |
| const Expr *SecondBuf, |
| const char *firstMessage = NULL, |
| const char *secondMessage = NULL, |
| bool WarnAboutSize = false) const; |
| const GRState *CheckBufferAccess(CheckerContext &C, const GRState *state, |
| const Expr *Size, const Expr *Buf, |
| const char *message = NULL, |
| bool WarnAboutSize = false) const { |
| // This is a convenience override. |
| return CheckBufferAccess(C, state, Size, Buf, NULL, message, NULL, |
| WarnAboutSize); |
| } |
| const GRState *CheckOverlap(CheckerContext &C, const GRState *state, |
| const Expr *Size, const Expr *First, |
| const Expr *Second) const; |
| void emitOverlapBug(CheckerContext &C, const GRState *state, |
| const Stmt *First, const Stmt *Second) const; |
| const GRState *checkAdditionOverflow(CheckerContext &C, const GRState *state, |
| NonLoc left, NonLoc right) const; |
| }; |
| |
| class CStringLength { |
| public: |
| typedef llvm::ImmutableMap<const MemRegion *, SVal> EntryMap; |
| }; |
| } //end anonymous namespace |
| |
| namespace clang { |
| namespace ento { |
| template <> |
| struct GRStateTrait<CStringLength> |
| : public GRStatePartialTrait<CStringLength::EntryMap> { |
| static void *GDMIndex() { return CStringChecker::getTag(); } |
| }; |
| } |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Individual checks and utility methods. |
| //===----------------------------------------------------------------------===// |
| |
| std::pair<const GRState*, const GRState*> |
| CStringChecker::assumeZero(CheckerContext &C, const GRState *state, SVal V, |
| QualType Ty) { |
| DefinedSVal *val = dyn_cast<DefinedSVal>(&V); |
| if (!val) |
| return std::pair<const GRState*, const GRState *>(state, state); |
| |
| SValBuilder &svalBuilder = C.getSValBuilder(); |
| DefinedOrUnknownSVal zero = svalBuilder.makeZeroVal(Ty); |
| return state->assume(svalBuilder.evalEQ(state, *val, zero)); |
| } |
| |
| const GRState *CStringChecker::checkNonNull(CheckerContext &C, |
| const GRState *state, |
| const Expr *S, SVal l) const { |
| // If a previous check has failed, propagate the failure. |
| if (!state) |
| return NULL; |
| |
| const GRState *stateNull, *stateNonNull; |
| llvm::tie(stateNull, stateNonNull) = assumeZero(C, state, l, S->getType()); |
| |
| if (stateNull && !stateNonNull) { |
| ExplodedNode *N = C.generateSink(stateNull); |
| if (!N) |
| return NULL; |
| |
| if (!BT_Null) |
| BT_Null.reset(new BuiltinBug("API", |
| "Null pointer argument in call to byte string function")); |
| |
| llvm::SmallString<80> buf; |
| llvm::raw_svector_ostream os(buf); |
| assert(CurrentFunctionDescription); |
| os << "Null pointer argument in call to " << CurrentFunctionDescription; |
| |
| // Generate a report for this bug. |
| BuiltinBug *BT = static_cast<BuiltinBug*>(BT_Null.get()); |
| EnhancedBugReport *report = new EnhancedBugReport(*BT, os.str(), N); |
| |
| report->addRange(S->getSourceRange()); |
| report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue, S); |
| C.EmitReport(report); |
| return NULL; |
| } |
| |
| // From here on, assume that the value is non-null. |
| assert(stateNonNull); |
| return stateNonNull; |
| } |
| |
| // FIXME: This was originally copied from ArrayBoundChecker.cpp. Refactor? |
| const GRState *CStringChecker::CheckLocation(CheckerContext &C, |
| const GRState *state, |
| const Expr *S, SVal l, |
| const char *warningMsg) const { |
| // If a previous check has failed, propagate the failure. |
| if (!state) |
| return NULL; |
| |
| // Check for out of bound array element access. |
| const MemRegion *R = l.getAsRegion(); |
| if (!R) |
| return state; |
| |
| const ElementRegion *ER = dyn_cast<ElementRegion>(R); |
| if (!ER) |
| return state; |
| |
| assert(ER->getValueType() == C.getASTContext().CharTy && |
| "CheckLocation should only be called with char* ElementRegions"); |
| |
| // Get the size of the array. |
| const SubRegion *superReg = cast<SubRegion>(ER->getSuperRegion()); |
| SValBuilder &svalBuilder = C.getSValBuilder(); |
| SVal Extent = |
| svalBuilder.convertToArrayIndex(superReg->getExtent(svalBuilder)); |
| DefinedOrUnknownSVal Size = cast<DefinedOrUnknownSVal>(Extent); |
| |
| // Get the index of the accessed element. |
| DefinedOrUnknownSVal Idx = cast<DefinedOrUnknownSVal>(ER->getIndex()); |
| |
| const GRState *StInBound = state->assumeInBound(Idx, Size, true); |
| const GRState *StOutBound = state->assumeInBound(Idx, Size, false); |
| if (StOutBound && !StInBound) { |
| ExplodedNode *N = C.generateSink(StOutBound); |
| if (!N) |
| return NULL; |
| |
| if (!BT_Bounds) { |
| BT_Bounds.reset(new BuiltinBug("Out-of-bound array access", |
| "Byte string function accesses out-of-bound array element")); |
| } |
| BuiltinBug *BT = static_cast<BuiltinBug*>(BT_Bounds.get()); |
| |
| // Generate a report for this bug. |
| RangedBugReport *report; |
| if (warningMsg) { |
| report = new RangedBugReport(*BT, warningMsg, N); |
| } else { |
| assert(CurrentFunctionDescription); |
| assert(CurrentFunctionDescription[0] != '\0'); |
| |
| llvm::SmallString<80> buf; |
| llvm::raw_svector_ostream os(buf); |
| os << (char)toupper(CurrentFunctionDescription[0]) |
| << &CurrentFunctionDescription[1] |
| << " accesses out-of-bound array element"; |
| report = new RangedBugReport(*BT, os.str(), N); |
| } |
| |
| // FIXME: It would be nice to eventually make this diagnostic more clear, |
| // e.g., by referencing the original declaration or by saying *why* this |
| // reference is outside the range. |
| |
| report->addRange(S->getSourceRange()); |
| C.EmitReport(report); |
| return NULL; |
| } |
| |
| // Array bound check succeeded. From this point forward the array bound |
| // should always succeed. |
| return StInBound; |
| } |
| |
| const GRState *CStringChecker::CheckBufferAccess(CheckerContext &C, |
| const GRState *state, |
| const Expr *Size, |
| const Expr *FirstBuf, |
| const Expr *SecondBuf, |
| const char *firstMessage, |
| const char *secondMessage, |
| bool WarnAboutSize) const { |
| // If a previous check has failed, propagate the failure. |
| if (!state) |
| return NULL; |
| |
| SValBuilder &svalBuilder = C.getSValBuilder(); |
| ASTContext &Ctx = svalBuilder.getContext(); |
| |
| QualType sizeTy = Size->getType(); |
| QualType PtrTy = Ctx.getPointerType(Ctx.CharTy); |
| |
| // Check that the first buffer is non-null. |
| SVal BufVal = state->getSVal(FirstBuf); |
| state = checkNonNull(C, state, FirstBuf, BufVal); |
| if (!state) |
| return NULL; |
| |
| // Get the access length and make sure it is known. |
| // FIXME: This assumes the caller has already checked that the access length |
| // is positive. And that it's unsigned. |
| SVal LengthVal = state->getSVal(Size); |
| NonLoc *Length = dyn_cast<NonLoc>(&LengthVal); |
| if (!Length) |
| return state; |
| |
| // Compute the offset of the last element to be accessed: size-1. |
| NonLoc One = cast<NonLoc>(svalBuilder.makeIntVal(1, sizeTy)); |
| NonLoc LastOffset = cast<NonLoc>(svalBuilder.evalBinOpNN(state, BO_Sub, |
| *Length, One, sizeTy)); |
| |
| // Check that the first buffer is sufficiently long. |
| SVal BufStart = svalBuilder.evalCast(BufVal, PtrTy, FirstBuf->getType()); |
| if (Loc *BufLoc = dyn_cast<Loc>(&BufStart)) { |
| const Expr *warningExpr = (WarnAboutSize ? Size : FirstBuf); |
| |
| SVal BufEnd = svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc, |
| LastOffset, PtrTy); |
| state = CheckLocation(C, state, warningExpr, BufEnd, firstMessage); |
| |
| // If the buffer isn't large enough, abort. |
| if (!state) |
| return NULL; |
| } |
| |
| // If there's a second buffer, check it as well. |
| if (SecondBuf) { |
| BufVal = state->getSVal(SecondBuf); |
| state = checkNonNull(C, state, SecondBuf, BufVal); |
| if (!state) |
| return NULL; |
| |
| BufStart = svalBuilder.evalCast(BufVal, PtrTy, SecondBuf->getType()); |
| if (Loc *BufLoc = dyn_cast<Loc>(&BufStart)) { |
| const Expr *warningExpr = (WarnAboutSize ? Size : SecondBuf); |
| |
| SVal BufEnd = svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc, |
| LastOffset, PtrTy); |
| state = CheckLocation(C, state, warningExpr, BufEnd, secondMessage); |
| } |
| } |
| |
| // Large enough or not, return this state! |
| return state; |
| } |
| |
| const GRState *CStringChecker::CheckOverlap(CheckerContext &C, |
| const GRState *state, |
| const Expr *Size, |
| const Expr *First, |
| const Expr *Second) const { |
| // Do a simple check for overlap: if the two arguments are from the same |
| // buffer, see if the end of the first is greater than the start of the second |
| // or vice versa. |
| |
| // If a previous check has failed, propagate the failure. |
| if (!state) |
| return NULL; |
| |
| const GRState *stateTrue, *stateFalse; |
| |
| // Get the buffer values and make sure they're known locations. |
| SVal firstVal = state->getSVal(First); |
| SVal secondVal = state->getSVal(Second); |
| |
| Loc *firstLoc = dyn_cast<Loc>(&firstVal); |
| if (!firstLoc) |
| return state; |
| |
| Loc *secondLoc = dyn_cast<Loc>(&secondVal); |
| if (!secondLoc) |
| return state; |
| |
| // Are the two values the same? |
| SValBuilder &svalBuilder = C.getSValBuilder(); |
| llvm::tie(stateTrue, stateFalse) = |
| state->assume(svalBuilder.evalEQ(state, *firstLoc, *secondLoc)); |
| |
| if (stateTrue && !stateFalse) { |
| // If the values are known to be equal, that's automatically an overlap. |
| emitOverlapBug(C, stateTrue, First, Second); |
| return NULL; |
| } |
| |
| // assume the two expressions are not equal. |
| assert(stateFalse); |
| state = stateFalse; |
| |
| // Which value comes first? |
| QualType cmpTy = svalBuilder.getConditionType(); |
| SVal reverse = svalBuilder.evalBinOpLL(state, BO_GT, |
| *firstLoc, *secondLoc, cmpTy); |
| DefinedOrUnknownSVal *reverseTest = dyn_cast<DefinedOrUnknownSVal>(&reverse); |
| if (!reverseTest) |
| return state; |
| |
| llvm::tie(stateTrue, stateFalse) = state->assume(*reverseTest); |
| if (stateTrue) { |
| if (stateFalse) { |
| // If we don't know which one comes first, we can't perform this test. |
| return state; |
| } else { |
| // Switch the values so that firstVal is before secondVal. |
| Loc *tmpLoc = firstLoc; |
| firstLoc = secondLoc; |
| secondLoc = tmpLoc; |
| |
| // Switch the Exprs as well, so that they still correspond. |
| const Expr *tmpExpr = First; |
| First = Second; |
| Second = tmpExpr; |
| } |
| } |
| |
| // Get the length, and make sure it too is known. |
| SVal LengthVal = state->getSVal(Size); |
| NonLoc *Length = dyn_cast<NonLoc>(&LengthVal); |
| if (!Length) |
| return state; |
| |
| // Convert the first buffer's start address to char*. |
| // Bail out if the cast fails. |
| ASTContext &Ctx = svalBuilder.getContext(); |
| QualType CharPtrTy = Ctx.getPointerType(Ctx.CharTy); |
| SVal FirstStart = svalBuilder.evalCast(*firstLoc, CharPtrTy, |
| First->getType()); |
| Loc *FirstStartLoc = dyn_cast<Loc>(&FirstStart); |
| if (!FirstStartLoc) |
| return state; |
| |
| // Compute the end of the first buffer. Bail out if THAT fails. |
| SVal FirstEnd = svalBuilder.evalBinOpLN(state, BO_Add, |
| *FirstStartLoc, *Length, CharPtrTy); |
| Loc *FirstEndLoc = dyn_cast<Loc>(&FirstEnd); |
| if (!FirstEndLoc) |
| return state; |
| |
| // Is the end of the first buffer past the start of the second buffer? |
| SVal Overlap = svalBuilder.evalBinOpLL(state, BO_GT, |
| *FirstEndLoc, *secondLoc, cmpTy); |
| DefinedOrUnknownSVal *OverlapTest = dyn_cast<DefinedOrUnknownSVal>(&Overlap); |
| if (!OverlapTest) |
| return state; |
| |
| llvm::tie(stateTrue, stateFalse) = state->assume(*OverlapTest); |
| |
| if (stateTrue && !stateFalse) { |
| // Overlap! |
| emitOverlapBug(C, stateTrue, First, Second); |
| return NULL; |
| } |
| |
| // assume the two expressions don't overlap. |
| assert(stateFalse); |
| return stateFalse; |
| } |
| |
| void CStringChecker::emitOverlapBug(CheckerContext &C, const GRState *state, |
| const Stmt *First, const Stmt *Second) const { |
| ExplodedNode *N = C.generateSink(state); |
| if (!N) |
| return; |
| |
| if (!BT_Overlap) |
| BT_Overlap.reset(new BugType("Unix API", "Improper arguments")); |
| |
| // Generate a report for this bug. |
| RangedBugReport *report = |
| new RangedBugReport(*BT_Overlap, |
| "Arguments must not be overlapping buffers", N); |
| report->addRange(First->getSourceRange()); |
| report->addRange(Second->getSourceRange()); |
| |
| C.EmitReport(report); |
| } |
| |
| const GRState *CStringChecker::checkAdditionOverflow(CheckerContext &C, |
| const GRState *state, |
| NonLoc left, |
| NonLoc right) const { |
| // If a previous check has failed, propagate the failure. |
| if (!state) |
| return NULL; |
| |
| SValBuilder &svalBuilder = C.getSValBuilder(); |
| BasicValueFactory &BVF = svalBuilder.getBasicValueFactory(); |
| |
| QualType sizeTy = svalBuilder.getContext().getSizeType(); |
| const llvm::APSInt &maxValInt = BVF.getMaxValue(sizeTy); |
| NonLoc maxVal = svalBuilder.makeIntVal(maxValInt); |
| |
| SVal maxMinusRight = svalBuilder.evalBinOpNN(state, BO_Sub, maxVal, right, |
| sizeTy); |
| |
| if (maxMinusRight.isUnknownOrUndef()) { |
| // Try switching the operands. (The order of these two assignments is |
| // important!) |
| maxMinusRight = svalBuilder.evalBinOpNN(state, BO_Sub, maxVal, left, |
| sizeTy); |
| left = right; |
| } |
| |
| if (NonLoc *maxMinusRightNL = dyn_cast<NonLoc>(&maxMinusRight)) { |
| QualType cmpTy = svalBuilder.getConditionType(); |
| // If left > max - right, we have an overflow. |
| SVal willOverflow = svalBuilder.evalBinOpNN(state, BO_GT, left, |
| *maxMinusRightNL, cmpTy); |
| |
| const GRState *stateOverflow, *stateOkay; |
| llvm::tie(stateOverflow, stateOkay) = |
| state->assume(cast<DefinedOrUnknownSVal>(willOverflow)); |
| |
| if (stateOverflow && !stateOkay) { |
| // We have an overflow. Emit a bug report. |
| ExplodedNode *N = C.generateSink(stateOverflow); |
| if (!N) |
| return NULL; |
| |
| if (!BT_AdditionOverflow) |
| BT_AdditionOverflow.reset(new BuiltinBug("API", |
| "Sum of expressions causes overflow")); |
| |
| // This isn't a great error message, but this should never occur in real |
| // code anyway -- you'd have to create a buffer longer than a size_t can |
| // represent, which is sort of a contradiction. |
| const char *warning = |
| "This expression will create a string whose length is too big to " |
| "be represented as a size_t"; |
| |
| // Generate a report for this bug. |
| BugReport *report = new BugReport(*BT_AdditionOverflow, warning, N); |
| C.EmitReport(report); |
| |
| return NULL; |
| } |
| |
| // From now on, assume an overflow didn't occur. |
| assert(stateOkay); |
| state = stateOkay; |
| } |
| |
| return state; |
| } |
| |
| const GRState *CStringChecker::setCStringLength(const GRState *state, |
| const MemRegion *MR, |
| SVal strLength) { |
| assert(!strLength.isUndef() && "Attempt to set an undefined string length"); |
| |
| MR = MR->StripCasts(); |
| |
| switch (MR->getKind()) { |
| case MemRegion::StringRegionKind: |
| // FIXME: This can happen if we strcpy() into a string region. This is |
| // undefined [C99 6.4.5p6], but we should still warn about it. |
| return state; |
| |
| case MemRegion::SymbolicRegionKind: |
| case MemRegion::AllocaRegionKind: |
| case MemRegion::VarRegionKind: |
| case MemRegion::FieldRegionKind: |
| case MemRegion::ObjCIvarRegionKind: |
| // These are the types we can currently track string lengths for. |
| break; |
| |
| case MemRegion::ElementRegionKind: |
| // FIXME: Handle element regions by upper-bounding the parent region's |
| // string length. |
| return state; |
| |
| default: |
| // Other regions (mostly non-data) can't have a reliable C string length. |
| // For now, just ignore the change. |
| // FIXME: These are rare but not impossible. We should output some kind of |
| // warning for things like strcpy((char[]){'a', 0}, "b"); |
| return state; |
| } |
| |
| if (strLength.isUnknown()) |
| return state->remove<CStringLength>(MR); |
| |
| return state->set<CStringLength>(MR, strLength); |
| } |
| |
| SVal CStringChecker::getCStringLengthForRegion(CheckerContext &C, |
| const GRState *&state, |
| const Expr *Ex, |
| const MemRegion *MR, |
| bool hypothetical) { |
| if (!hypothetical) { |
| // If there's a recorded length, go ahead and return it. |
| const SVal *Recorded = state->get<CStringLength>(MR); |
| if (Recorded) |
| return *Recorded; |
| } |
| |
| // Otherwise, get a new symbol and update the state. |
| unsigned Count = C.getNodeBuilder().getCurrentBlockCount(); |
| SValBuilder &svalBuilder = C.getSValBuilder(); |
| QualType sizeTy = svalBuilder.getContext().getSizeType(); |
| SVal strLength = svalBuilder.getMetadataSymbolVal(CStringChecker::getTag(), |
| MR, Ex, sizeTy, Count); |
| |
| if (!hypothetical) |
| state = state->set<CStringLength>(MR, strLength); |
| |
| return strLength; |
| } |
| |
| SVal CStringChecker::getCStringLength(CheckerContext &C, const GRState *&state, |
| const Expr *Ex, SVal Buf, |
| bool hypothetical) const { |
| const MemRegion *MR = Buf.getAsRegion(); |
| if (!MR) { |
| // If we can't get a region, see if it's something we /know/ isn't a |
| // C string. In the context of locations, the only time we can issue such |
| // a warning is for labels. |
| if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&Buf)) { |
| if (ExplodedNode *N = C.generateNode(state)) { |
| if (!BT_NotCString) |
| BT_NotCString.reset(new BuiltinBug("API", |
| "Argument is not a null-terminated string.")); |
| |
| llvm::SmallString<120> buf; |
| llvm::raw_svector_ostream os(buf); |
| assert(CurrentFunctionDescription); |
| os << "Argument to " << CurrentFunctionDescription |
| << " is the address of the label '" << Label->getLabel()->getName() |
| << "', which is not a null-terminated string"; |
| |
| // Generate a report for this bug. |
| EnhancedBugReport *report = new EnhancedBugReport(*BT_NotCString, |
| os.str(), N); |
| |
| report->addRange(Ex->getSourceRange()); |
| C.EmitReport(report); |
| } |
| |
| return UndefinedVal(); |
| } |
| |
| // If it's not a region and not a label, give up. |
| return UnknownVal(); |
| } |
| |
| // If we have a region, strip casts from it and see if we can figure out |
| // its length. For anything we can't figure out, just return UnknownVal. |
| MR = MR->StripCasts(); |
| |
| switch (MR->getKind()) { |
| case MemRegion::StringRegionKind: { |
| // Modifying the contents of string regions is undefined [C99 6.4.5p6], |
| // so we can assume that the byte length is the correct C string length. |
| SValBuilder &svalBuilder = C.getSValBuilder(); |
| QualType sizeTy = svalBuilder.getContext().getSizeType(); |
| const StringLiteral *strLit = cast<StringRegion>(MR)->getStringLiteral(); |
| return svalBuilder.makeIntVal(strLit->getByteLength(), sizeTy); |
| } |
| case MemRegion::SymbolicRegionKind: |
| case MemRegion::AllocaRegionKind: |
| case MemRegion::VarRegionKind: |
| case MemRegion::FieldRegionKind: |
| case MemRegion::ObjCIvarRegionKind: |
| return getCStringLengthForRegion(C, state, Ex, MR, hypothetical); |
| case MemRegion::CompoundLiteralRegionKind: |
| // FIXME: Can we track this? Is it necessary? |
| return UnknownVal(); |
| case MemRegion::ElementRegionKind: |
| // FIXME: How can we handle this? It's not good enough to subtract the |
| // offset from the base string length; consider "123\x00567" and &a[5]. |
| return UnknownVal(); |
| default: |
| // Other regions (mostly non-data) can't have a reliable C string length. |
| // In this case, an error is emitted and UndefinedVal is returned. |
| // The caller should always be prepared to handle this case. |
| if (ExplodedNode *N = C.generateNode(state)) { |
| if (!BT_NotCString) |
| BT_NotCString.reset(new BuiltinBug("API", |
| "Argument is not a null-terminated string.")); |
| |
| llvm::SmallString<120> buf; |
| llvm::raw_svector_ostream os(buf); |
| |
| assert(CurrentFunctionDescription); |
| os << "Argument to " << CurrentFunctionDescription << " is "; |
| |
| if (SummarizeRegion(os, C.getASTContext(), MR)) |
| os << ", which is not a null-terminated string"; |
| else |
| os << "not a null-terminated string"; |
| |
| // Generate a report for this bug. |
| EnhancedBugReport *report = new EnhancedBugReport(*BT_NotCString, |
| os.str(), N); |
| |
| report->addRange(Ex->getSourceRange()); |
| C.EmitReport(report); |
| } |
| |
| return UndefinedVal(); |
| } |
| } |
| |
| const StringLiteral *CStringChecker::getCStringLiteral(CheckerContext &C, |
| const GRState *&state, const Expr *expr, SVal val) const { |
| |
| // Get the memory region pointed to by the val. |
| const MemRegion *bufRegion = val.getAsRegion(); |
| if (!bufRegion) |
| return NULL; |
| |
| // Strip casts off the memory region. |
| bufRegion = bufRegion->StripCasts(); |
| |
| // Cast the memory region to a string region. |
| const StringRegion *strRegion= dyn_cast<StringRegion>(bufRegion); |
| if (!strRegion) |
| return NULL; |
| |
| // Return the actual string in the string region. |
| return strRegion->getStringLiteral(); |
| } |
| |
| const GRState *CStringChecker::InvalidateBuffer(CheckerContext &C, |
| const GRState *state, |
| const Expr *E, SVal V) { |
| Loc *L = dyn_cast<Loc>(&V); |
| if (!L) |
| return state; |
| |
| // FIXME: This is a simplified version of what's in CFRefCount.cpp -- it makes |
| // some assumptions about the value that CFRefCount can't. Even so, it should |
| // probably be refactored. |
| if (loc::MemRegionVal* MR = dyn_cast<loc::MemRegionVal>(L)) { |
| const MemRegion *R = MR->getRegion()->StripCasts(); |
| |
| // Are we dealing with an ElementRegion? If so, we should be invalidating |
| // the super-region. |
| if (const ElementRegion *ER = dyn_cast<ElementRegion>(R)) { |
| R = ER->getSuperRegion(); |
| // FIXME: What about layers of ElementRegions? |
| } |
| |
| // Invalidate this region. |
| unsigned Count = C.getNodeBuilder().getCurrentBlockCount(); |
| return state->invalidateRegion(R, E, Count, NULL); |
| } |
| |
| // If we have a non-region value by chance, just remove the binding. |
| // FIXME: is this necessary or correct? This handles the non-Region |
| // cases. Is it ever valid to store to these? |
| return state->unbindLoc(*L); |
| } |
| |
| bool CStringChecker::SummarizeRegion(raw_ostream &os, ASTContext &Ctx, |
| const MemRegion *MR) { |
| const TypedValueRegion *TVR = dyn_cast<TypedValueRegion>(MR); |
| |
| switch (MR->getKind()) { |
| case MemRegion::FunctionTextRegionKind: { |
| const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl(); |
| if (FD) |
| os << "the address of the function '" << FD << "'"; |
| else |
| os << "the address of a function"; |
| return true; |
| } |
| case MemRegion::BlockTextRegionKind: |
| os << "block text"; |
| return true; |
| case MemRegion::BlockDataRegionKind: |
| os << "a block"; |
| return true; |
| case MemRegion::CXXThisRegionKind: |
| case MemRegion::CXXTempObjectRegionKind: |
| os << "a C++ temp object of type " << TVR->getValueType().getAsString(); |
| return true; |
| case MemRegion::VarRegionKind: |
| os << "a variable of type" << TVR->getValueType().getAsString(); |
| return true; |
| case MemRegion::FieldRegionKind: |
| os << "a field of type " << TVR->getValueType().getAsString(); |
| return true; |
| case MemRegion::ObjCIvarRegionKind: |
| os << "an instance variable of type " << TVR->getValueType().getAsString(); |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // evaluation of individual function calls. |
| //===----------------------------------------------------------------------===// |
| |
| void CStringChecker::evalCopyCommon(CheckerContext &C, |
| const CallExpr *CE, |
| const GRState *state, |
| const Expr *Size, const Expr *Dest, |
| const Expr *Source, bool Restricted, |
| bool IsMempcpy) const { |
| CurrentFunctionDescription = "memory copy function"; |
| |
| // See if the size argument is zero. |
| SVal sizeVal = state->getSVal(Size); |
| QualType sizeTy = Size->getType(); |
| |
| const GRState *stateZeroSize, *stateNonZeroSize; |
| llvm::tie(stateZeroSize, stateNonZeroSize) = |
| assumeZero(C, state, sizeVal, sizeTy); |
| |
| // Get the value of the Dest. |
| SVal destVal = state->getSVal(Dest); |
| |
| // If the size is zero, there won't be any actual memory access, so |
| // just bind the return value to the destination buffer and return. |
| if (stateZeroSize) { |
| stateZeroSize = stateZeroSize->BindExpr(CE, destVal); |
| C.addTransition(stateZeroSize); |
| } |
| |
| // If the size can be nonzero, we have to check the other arguments. |
| if (stateNonZeroSize) { |
| state = stateNonZeroSize; |
| |
| // Ensure the destination is not null. If it is NULL there will be a |
| // NULL pointer dereference. |
| state = checkNonNull(C, state, Dest, destVal); |
| if (!state) |
| return; |
| |
| // Get the value of the Src. |
| SVal srcVal = state->getSVal(Source); |
| |
| // Ensure the source is not null. If it is NULL there will be a |
| // NULL pointer dereference. |
| state = checkNonNull(C, state, Source, srcVal); |
| if (!state) |
| return; |
| |
| // Ensure the accesses are valid and that the buffers do not overlap. |
| const char * const writeWarning = |
| "Memory copy function overflows destination buffer"; |
| state = CheckBufferAccess(C, state, Size, Dest, Source, |
| writeWarning, /* sourceWarning = */ NULL); |
| if (Restricted) |
| state = CheckOverlap(C, state, Size, Dest, Source); |
| |
| if (!state) |
| return; |
| |
| // If this is mempcpy, get the byte after the last byte copied and |
| // bind the expr. |
| if (IsMempcpy) { |
| loc::MemRegionVal *destRegVal = dyn_cast<loc::MemRegionVal>(&destVal); |
| assert(destRegVal && "Destination should be a known MemRegionVal here"); |
| |
| // Get the length to copy. |
| NonLoc *lenValNonLoc = dyn_cast<NonLoc>(&sizeVal); |
| |
| if (lenValNonLoc) { |
| // Get the byte after the last byte copied. |
| SVal lastElement = C.getSValBuilder().evalBinOpLN(state, BO_Add, |
| *destRegVal, |
| *lenValNonLoc, |
| Dest->getType()); |
| |
| // The byte after the last byte copied is the return value. |
| state = state->BindExpr(CE, lastElement); |
| } else { |
| // If we don't know how much we copied, we can at least |
| // conjure a return value for later. |
| unsigned Count = C.getNodeBuilder().getCurrentBlockCount(); |
| SVal result = |
| C.getSValBuilder().getConjuredSymbolVal(NULL, CE, Count); |
| state = state->BindExpr(CE, result); |
| } |
| |
| } else { |
| // All other copies return the destination buffer. |
| // (Well, bcopy() has a void return type, but this won't hurt.) |
| state = state->BindExpr(CE, destVal); |
| } |
| |
| // Invalidate the destination. |
| // FIXME: Even if we can't perfectly model the copy, we should see if we |
| // can use LazyCompoundVals to copy the source values into the destination. |
| // This would probably remove any existing bindings past the end of the |
| // copied region, but that's still an improvement over blank invalidation. |
| state = InvalidateBuffer(C, state, Dest, state->getSVal(Dest)); |
| C.addTransition(state); |
| } |
| } |
| |
| |
| void CStringChecker::evalMemcpy(CheckerContext &C, const CallExpr *CE) const { |
| // void *memcpy(void *restrict dst, const void *restrict src, size_t n); |
| // The return value is the address of the destination buffer. |
| const Expr *Dest = CE->getArg(0); |
| const GRState *state = C.getState(); |
| |
| evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1), true); |
| } |
| |
| void CStringChecker::evalMempcpy(CheckerContext &C, const CallExpr *CE) const { |
| // void *mempcpy(void *restrict dst, const void *restrict src, size_t n); |
| // The return value is a pointer to the byte following the last written byte. |
| const Expr *Dest = CE->getArg(0); |
| const GRState *state = C.getState(); |
| |
| evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1), true, true); |
| } |
| |
| void CStringChecker::evalMemmove(CheckerContext &C, const CallExpr *CE) const { |
| // void *memmove(void *dst, const void *src, size_t n); |
| // The return value is the address of the destination buffer. |
| const Expr *Dest = CE->getArg(0); |
| const GRState *state = C.getState(); |
| |
| evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1)); |
| } |
| |
| void CStringChecker::evalBcopy(CheckerContext &C, const CallExpr *CE) const { |
| // void bcopy(const void *src, void *dst, size_t n); |
| evalCopyCommon(C, CE, C.getState(), |
| CE->getArg(2), CE->getArg(1), CE->getArg(0)); |
| } |
| |
| void CStringChecker::evalMemcmp(CheckerContext &C, const CallExpr *CE) const { |
| // int memcmp(const void *s1, const void *s2, size_t n); |
| CurrentFunctionDescription = "memory comparison function"; |
| |
| const Expr *Left = CE->getArg(0); |
| const Expr *Right = CE->getArg(1); |
| const Expr *Size = CE->getArg(2); |
| |
| const GRState *state = C.getState(); |
| SValBuilder &svalBuilder = C.getSValBuilder(); |
| |
| // See if the size argument is zero. |
| SVal sizeVal = state->getSVal(Size); |
| QualType sizeTy = Size->getType(); |
| |
| const GRState *stateZeroSize, *stateNonZeroSize; |
| llvm::tie(stateZeroSize, stateNonZeroSize) = |
| assumeZero(C, state, sizeVal, sizeTy); |
| |
| // If the size can be zero, the result will be 0 in that case, and we don't |
| // have to check either of the buffers. |
| if (stateZeroSize) { |
| state = stateZeroSize; |
| state = state->BindExpr(CE, svalBuilder.makeZeroVal(CE->getType())); |
| C.addTransition(state); |
| } |
| |
| // If the size can be nonzero, we have to check the other arguments. |
| if (stateNonZeroSize) { |
| state = stateNonZeroSize; |
| // If we know the two buffers are the same, we know the result is 0. |
| // First, get the two buffers' addresses. Another checker will have already |
| // made sure they're not undefined. |
| DefinedOrUnknownSVal LV = cast<DefinedOrUnknownSVal>(state->getSVal(Left)); |
| DefinedOrUnknownSVal RV = cast<DefinedOrUnknownSVal>(state->getSVal(Right)); |
| |
| // See if they are the same. |
| DefinedOrUnknownSVal SameBuf = svalBuilder.evalEQ(state, LV, RV); |
| const GRState *StSameBuf, *StNotSameBuf; |
| llvm::tie(StSameBuf, StNotSameBuf) = state->assume(SameBuf); |
| |
| // If the two arguments might be the same buffer, we know the result is 0, |
| // and we only need to check one size. |
| if (StSameBuf) { |
| state = StSameBuf; |
| state = CheckBufferAccess(C, state, Size, Left); |
| if (state) { |
| state = StSameBuf->BindExpr(CE, svalBuilder.makeZeroVal(CE->getType())); |
| C.addTransition(state); |
| } |
| } |
| |
| // If the two arguments might be different buffers, we have to check the |
| // size of both of them. |
| if (StNotSameBuf) { |
| state = StNotSameBuf; |
| state = CheckBufferAccess(C, state, Size, Left, Right); |
| if (state) { |
| // The return value is the comparison result, which we don't know. |
| unsigned Count = C.getNodeBuilder().getCurrentBlockCount(); |
| SVal CmpV = svalBuilder.getConjuredSymbolVal(NULL, CE, Count); |
| state = state->BindExpr(CE, CmpV); |
| C.addTransition(state); |
| } |
| } |
| } |
| } |
| |
| void CStringChecker::evalstrLength(CheckerContext &C, |
| const CallExpr *CE) const { |
| // size_t strlen(const char *s); |
| evalstrLengthCommon(C, CE, /* IsStrnlen = */ false); |
| } |
| |
| void CStringChecker::evalstrnLength(CheckerContext &C, |
| const CallExpr *CE) const { |
| // size_t strnlen(const char *s, size_t maxlen); |
| evalstrLengthCommon(C, CE, /* IsStrnlen = */ true); |
| } |
| |
| void CStringChecker::evalstrLengthCommon(CheckerContext &C, const CallExpr *CE, |
| bool IsStrnlen) const { |
| CurrentFunctionDescription = "string length function"; |
| const GRState *state = C.getState(); |
| |
| if (IsStrnlen) { |
| const Expr *maxlenExpr = CE->getArg(1); |
| SVal maxlenVal = state->getSVal(maxlenExpr); |
| |
| const GRState *stateZeroSize, *stateNonZeroSize; |
| llvm::tie(stateZeroSize, stateNonZeroSize) = |
| assumeZero(C, state, maxlenVal, maxlenExpr->getType()); |
| |
| // If the size can be zero, the result will be 0 in that case, and we don't |
| // have to check the string itself. |
| if (stateZeroSize) { |
| SVal zero = C.getSValBuilder().makeZeroVal(CE->getType()); |
| stateZeroSize = stateZeroSize->BindExpr(CE, zero); |
| C.addTransition(stateZeroSize); |
| } |
| |
| // If the size is GUARANTEED to be zero, we're done! |
| if (!stateNonZeroSize) |
| return; |
| |
| // Otherwise, record the assumption that the size is nonzero. |
| state = stateNonZeroSize; |
| } |
| |
| // Check that the string argument is non-null. |
| const Expr *Arg = CE->getArg(0); |
| SVal ArgVal = state->getSVal(Arg); |
| |
| state = checkNonNull(C, state, Arg, ArgVal); |
| |
| if (!state) |
| return; |
| |
| SVal strLength = getCStringLength(C, state, Arg, ArgVal); |
| |
| // If the argument isn't a valid C string, there's no valid state to |
| // transition to. |
| if (strLength.isUndef()) |
| return; |
| |
| DefinedOrUnknownSVal result = UnknownVal(); |
| |
| // If the check is for strnlen() then bind the return value to no more than |
| // the maxlen value. |
| if (IsStrnlen) { |
| QualType cmpTy = C.getSValBuilder().getConditionType(); |
| |
| // It's a little unfortunate to be getting this again, |
| // but it's not that expensive... |
| const Expr *maxlenExpr = CE->getArg(1); |
| SVal maxlenVal = state->getSVal(maxlenExpr); |
| |
| NonLoc *strLengthNL = dyn_cast<NonLoc>(&strLength); |
| NonLoc *maxlenValNL = dyn_cast<NonLoc>(&maxlenVal); |
| |
| if (strLengthNL && maxlenValNL) { |
| const GRState *stateStringTooLong, *stateStringNotTooLong; |
| |
| // Check if the strLength is greater than the maxlen. |
| llvm::tie(stateStringTooLong, stateStringNotTooLong) = |
| state->assume(cast<DefinedOrUnknownSVal> |
| (C.getSValBuilder().evalBinOpNN(state, BO_GT, |
| *strLengthNL, |
| *maxlenValNL, |
| cmpTy))); |
| |
| if (stateStringTooLong && !stateStringNotTooLong) { |
| // If the string is longer than maxlen, return maxlen. |
| result = *maxlenValNL; |
| } else if (stateStringNotTooLong && !stateStringTooLong) { |
| // If the string is shorter than maxlen, return its length. |
| result = *strLengthNL; |
| } |
| } |
| |
| if (result.isUnknown()) { |
| // If we don't have enough information for a comparison, there's |
| // no guarantee the full string length will actually be returned. |
| // All we know is the return value is the min of the string length |
| // and the limit. This is better than nothing. |
| unsigned Count = C.getNodeBuilder().getCurrentBlockCount(); |
| result = C.getSValBuilder().getConjuredSymbolVal(NULL, CE, Count); |
| NonLoc *resultNL = cast<NonLoc>(&result); |
| |
| if (strLengthNL) { |
| state = state->assume(cast<DefinedOrUnknownSVal> |
| (C.getSValBuilder().evalBinOpNN(state, BO_LE, |
| *resultNL, |
| *strLengthNL, |
| cmpTy)), true); |
| } |
| |
| if (maxlenValNL) { |
| state = state->assume(cast<DefinedOrUnknownSVal> |
| (C.getSValBuilder().evalBinOpNN(state, BO_LE, |
| *resultNL, |
| *maxlenValNL, |
| cmpTy)), true); |
| } |
| } |
| |
| } else { |
| // This is a plain strlen(), not strnlen(). |
| result = cast<DefinedOrUnknownSVal>(strLength); |
| |
| // If we don't know the length of the string, conjure a return |
| // value, so it can be used in constraints, at least. |
| if (result.isUnknown()) { |
| unsigned Count = C.getNodeBuilder().getCurrentBlockCount(); |
| result = C.getSValBuilder().getConjuredSymbolVal(NULL, CE, Count); |
| } |
| } |
| |
| // Bind the return value. |
| assert(!result.isUnknown() && "Should have conjured a value by now"); |
| state = state->BindExpr(CE, result); |
| C.addTransition(state); |
| } |
| |
| void CStringChecker::evalStrcpy(CheckerContext &C, const CallExpr *CE) const { |
| // char *strcpy(char *restrict dst, const char *restrict src); |
| evalStrcpyCommon(C, CE, |
| /* returnEnd = */ false, |
| /* isBounded = */ false, |
| /* isAppending = */ false); |
| } |
| |
| void CStringChecker::evalStrncpy(CheckerContext &C, const CallExpr *CE) const { |
| // char *strncpy(char *restrict dst, const char *restrict src, size_t n); |
| evalStrcpyCommon(C, CE, |
| /* returnEnd = */ false, |
| /* isBounded = */ true, |
| /* isAppending = */ false); |
| } |
| |
| void CStringChecker::evalStpcpy(CheckerContext &C, const CallExpr *CE) const { |
| // char *stpcpy(char *restrict dst, const char *restrict src); |
| evalStrcpyCommon(C, CE, |
| /* returnEnd = */ true, |
| /* isBounded = */ false, |
| /* isAppending = */ false); |
| } |
| |
| void CStringChecker::evalStrcat(CheckerContext &C, const CallExpr *CE) const { |
| //char *strcat(char *restrict s1, const char *restrict s2); |
| evalStrcpyCommon(C, CE, |
| /* returnEnd = */ false, |
| /* isBounded = */ false, |
| /* isAppending = */ true); |
| } |
| |
| void CStringChecker::evalStrncat(CheckerContext &C, const CallExpr *CE) const { |
| //char *strncat(char *restrict s1, const char *restrict s2, size_t n); |
| evalStrcpyCommon(C, CE, |
| /* returnEnd = */ false, |
| /* isBounded = */ true, |
| /* isAppending = */ true); |
| } |
| |
| void CStringChecker::evalStrcpyCommon(CheckerContext &C, const CallExpr *CE, |
| bool returnEnd, bool isBounded, |
| bool isAppending) const { |
| CurrentFunctionDescription = "string copy function"; |
| const GRState *state = C.getState(); |
| |
| // Check that the destination is non-null. |
| const Expr *Dst = CE->getArg(0); |
| SVal DstVal = state->getSVal(Dst); |
| |
| state = checkNonNull(C, state, Dst, DstVal); |
| if (!state) |
| return; |
| |
| // Check that the source is non-null. |
| const Expr *srcExpr = CE->getArg(1); |
| SVal srcVal = state->getSVal(srcExpr); |
| state = checkNonNull(C, state, srcExpr, srcVal); |
| if (!state) |
| return; |
| |
| // Get the string length of the source. |
| SVal strLength = getCStringLength(C, state, srcExpr, srcVal); |
| |
| // If the source isn't a valid C string, give up. |
| if (strLength.isUndef()) |
| return; |
| |
| SValBuilder &svalBuilder = C.getSValBuilder(); |
| QualType cmpTy = svalBuilder.getConditionType(); |
| QualType sizeTy = svalBuilder.getContext().getSizeType(); |
| |
| // These two values allow checking two kinds of errors: |
| // - actual overflows caused by a source that doesn't fit in the destination |
| // - potential overflows caused by a bound that could exceed the destination |
| SVal amountCopied = UnknownVal(); |
| SVal maxLastElementIndex = UnknownVal(); |
| const char *boundWarning = NULL; |
| |
| // If the function is strncpy, strncat, etc... it is bounded. |
| if (isBounded) { |
| // Get the max number of characters to copy. |
| const Expr *lenExpr = CE->getArg(2); |
| SVal lenVal = state->getSVal(lenExpr); |
| |
| // Protect against misdeclared strncpy(). |
| lenVal = svalBuilder.evalCast(lenVal, sizeTy, lenExpr->getType()); |
| |
| NonLoc *strLengthNL = dyn_cast<NonLoc>(&strLength); |
| NonLoc *lenValNL = dyn_cast<NonLoc>(&lenVal); |
| |
| // If we know both values, we might be able to figure out how much |
| // we're copying. |
| if (strLengthNL && lenValNL) { |
| const GRState *stateSourceTooLong, *stateSourceNotTooLong; |
| |
| // Check if the max number to copy is less than the length of the src. |
| // If the bound is equal to the source length, strncpy won't null- |
| // terminate the result! |
| llvm::tie(stateSourceTooLong, stateSourceNotTooLong) = |
| state->assume(cast<DefinedOrUnknownSVal> |
| (svalBuilder.evalBinOpNN(state, BO_GE, *strLengthNL, |
| *lenValNL, cmpTy))); |
| |
| if (stateSourceTooLong && !stateSourceNotTooLong) { |
| // Max number to copy is less than the length of the src, so the actual |
| // strLength copied is the max number arg. |
| state = stateSourceTooLong; |
| amountCopied = lenVal; |
| |
| } else if (!stateSourceTooLong && stateSourceNotTooLong) { |
| // The source buffer entirely fits in the bound. |
| state = stateSourceNotTooLong; |
| amountCopied = strLength; |
| } |
| } |
| |
| // We still want to know if the bound is known to be too large. |
| if (lenValNL) { |
| if (isAppending) { |
| // For strncat, the check is strlen(dst) + lenVal < sizeof(dst) |
| |
| // Get the string length of the destination. If the destination is |
| // memory that can't have a string length, we shouldn't be copying |
| // into it anyway. |
| SVal dstStrLength = getCStringLength(C, state, Dst, DstVal); |
| if (dstStrLength.isUndef()) |
| return; |
| |
| if (NonLoc *dstStrLengthNL = dyn_cast<NonLoc>(&dstStrLength)) { |
| maxLastElementIndex = svalBuilder.evalBinOpNN(state, BO_Add, |
| *lenValNL, |
| *dstStrLengthNL, |
| sizeTy); |
| boundWarning = "Size argument is greater than the free space in the " |
| "destination buffer"; |
| } |
| |
| } else { |
| // For strncpy, this is just checking that lenVal <= sizeof(dst) |
| // (Yes, strncpy and strncat differ in how they treat termination. |
| // strncat ALWAYS terminates, but strncpy doesn't.) |
| NonLoc one = cast<NonLoc>(svalBuilder.makeIntVal(1, sizeTy)); |
| maxLastElementIndex = svalBuilder.evalBinOpNN(state, BO_Sub, *lenValNL, |
| one, sizeTy); |
| boundWarning = "Size argument is greater than the length of the " |
| "destination buffer"; |
| } |
| } |
| |
| // If we couldn't pin down the copy length, at least bound it. |
| // FIXME: We should actually run this code path for append as well, but |
| // right now it creates problems with constraints (since we can end up |
| // trying to pass constraints from symbol to symbol). |
| if (amountCopied.isUnknown() && !isAppending) { |
| // Try to get a "hypothetical" string length symbol, which we can later |
| // set as a real value if that turns out to be the case. |
| amountCopied = getCStringLength(C, state, lenExpr, srcVal, true); |
| assert(!amountCopied.isUndef()); |
| |
| if (NonLoc *amountCopiedNL = dyn_cast<NonLoc>(&amountCopied)) { |
| if (lenValNL) { |
| // amountCopied <= lenVal |
| SVal copiedLessThanBound = svalBuilder.evalBinOpNN(state, BO_LE, |
| *amountCopiedNL, |
| *lenValNL, |
| cmpTy); |
| state = state->assume(cast<DefinedOrUnknownSVal>(copiedLessThanBound), |
| true); |
| if (!state) |
| return; |
| } |
| |
| if (strLengthNL) { |
| // amountCopied <= strlen(source) |
| SVal copiedLessThanSrc = svalBuilder.evalBinOpNN(state, BO_LE, |
| *amountCopiedNL, |
| *strLengthNL, |
| cmpTy); |
| state = state->assume(cast<DefinedOrUnknownSVal>(copiedLessThanSrc), |
| true); |
| if (!state) |
| return; |
| } |
| } |
| } |
| |
| } else { |
| // The function isn't bounded. The amount copied should match the length |
| // of the source buffer. |
| amountCopied = strLength; |
| } |
| |
| assert(state); |
| |
| // This represents the number of characters copied into the destination |
| // buffer. (It may not actually be the strlen if the destination buffer |
| // is not terminated.) |
| SVal finalStrLength = UnknownVal(); |
| |
| // If this is an appending function (strcat, strncat...) then set the |
| // string length to strlen(src) + strlen(dst) since the buffer will |
| // ultimately contain both. |
| if (isAppending) { |
| // Get the string length of the destination. If the destination is memory |
| // that can't have a string length, we shouldn't be copying into it anyway. |
| SVal dstStrLength = getCStringLength(C, state, Dst, DstVal); |
| if (dstStrLength.isUndef()) |
| return; |
| |
| NonLoc *srcStrLengthNL = dyn_cast<NonLoc>(&amountCopied); |
| NonLoc *dstStrLengthNL = dyn_cast<NonLoc>(&dstStrLength); |
| |
| // If we know both string lengths, we might know the final string length. |
| if (srcStrLengthNL && dstStrLengthNL) { |
| // Make sure the two lengths together don't overflow a size_t. |
| state = checkAdditionOverflow(C, state, *srcStrLengthNL, *dstStrLengthNL); |
| if (!state) |
| return; |
| |
| finalStrLength = svalBuilder.evalBinOpNN(state, BO_Add, *srcStrLengthNL, |
| *dstStrLengthNL, sizeTy); |
| } |
| |
| // If we couldn't get a single value for the final string length, |
| // we can at least bound it by the individual lengths. |
| if (finalStrLength.isUnknown()) { |
| // Try to get a "hypothetical" string length symbol, which we can later |
| // set as a real value if that turns out to be the case. |
| finalStrLength = getCStringLength(C, state, CE, DstVal, true); |
| assert(!finalStrLength.isUndef()); |
| |
| if (NonLoc *finalStrLengthNL = dyn_cast<NonLoc>(&finalStrLength)) { |
| if (srcStrLengthNL) { |
| // finalStrLength >= srcStrLength |
| SVal sourceInResult = svalBuilder.evalBinOpNN(state, BO_GE, |
| *finalStrLengthNL, |
| *srcStrLengthNL, |
| cmpTy); |
| state = state->assume(cast<DefinedOrUnknownSVal>(sourceInResult), |
| true); |
| if (!state) |
| return; |
| } |
| |
| if (dstStrLengthNL) { |
| // finalStrLength >= dstStrLength |
| SVal destInResult = svalBuilder.evalBinOpNN(state, BO_GE, |
| *finalStrLengthNL, |
| *dstStrLengthNL, |
| cmpTy); |
| state = state->assume(cast<DefinedOrUnknownSVal>(destInResult), |
| true); |
| if (!state) |
| return; |
| } |
| } |
| } |
| |
| } else { |
| // Otherwise, this is a copy-over function (strcpy, strncpy, ...), and |
| // the final string length will match the input string length. |
| finalStrLength = amountCopied; |
| } |
| |
| // The final result of the function will either be a pointer past the last |
| // copied element, or a pointer to the start of the destination buffer. |
| SVal Result = (returnEnd ? UnknownVal() : DstVal); |
| |
| assert(state); |
| |
| // If the destination is a MemRegion, try to check for a buffer overflow and |
| // record the new string length. |
| if (loc::MemRegionVal *dstRegVal = dyn_cast<loc::MemRegionVal>(&DstVal)) { |
| QualType ptrTy = Dst->getType(); |
| |
| // If we have an exact value on a bounded copy, use that to check for |
| // overflows, rather than our estimate about how much is actually copied. |
| if (boundWarning) { |
| if (NonLoc *maxLastNL = dyn_cast<NonLoc>(&maxLastElementIndex)) { |
| SVal maxLastElement = svalBuilder.evalBinOpLN(state, BO_Add, *dstRegVal, |
| *maxLastNL, ptrTy); |
| state = CheckLocation(C, state, CE->getArg(2), maxLastElement, |
| boundWarning); |
| if (!state) |
| return; |
| } |
| } |
| |
| // Then, if the final length is known... |
| if (NonLoc *knownStrLength = dyn_cast<NonLoc>(&finalStrLength)) { |
| SVal lastElement = svalBuilder.evalBinOpLN(state, BO_Add, *dstRegVal, |
| *knownStrLength, ptrTy); |
| |
| // ...and we haven't checked the bound, we'll check the actual copy. |
| if (!boundWarning) { |
| const char * const warningMsg = |
| "String copy function overflows destination buffer"; |
| state = CheckLocation(C, state, Dst, lastElement, warningMsg); |
| if (!state) |
| return; |
| } |
| |
| // If this is a stpcpy-style copy, the last element is the return value. |
| if (returnEnd) |
| Result = lastElement; |
| } |
| |
| // Invalidate the destination. This must happen before we set the C string |
| // length because invalidation will clear the length. |
| // FIXME: Even if we can't perfectly model the copy, we should see if we |
| // can use LazyCompoundVals to copy the source values into the destination. |
| // This would probably remove any existing bindings past the end of the |
| // string, but that's still an improvement over blank invalidation. |
| state = InvalidateBuffer(C, state, Dst, *dstRegVal); |
| |
| // Set the C string length of the destination, if we know it. |
| if (isBounded && !isAppending) { |
| // strncpy is annoying in that it doesn't guarantee to null-terminate |
| // the result string. If the original string didn't fit entirely inside |
| // the bound (including the null-terminator), we don't know how long the |
| // result is. |
| if (amountCopied != strLength) |
| finalStrLength = UnknownVal(); |
| } |
| state = setCStringLength(state, dstRegVal->getRegion(), finalStrLength); |
| } |
| |
| assert(state); |
| |
| // If this is a stpcpy-style copy, but we were unable to check for a buffer |
| // overflow, we still need a result. Conjure a return value. |
| if (returnEnd && Result.isUnknown()) { |
| unsigned Count = C.getNodeBuilder().getCurrentBlockCount(); |
| Result = svalBuilder.getConjuredSymbolVal(NULL, CE, Count); |
| } |
| |
| // Set the return value. |
| state = state->BindExpr(CE, Result); |
| C.addTransition(state); |
| } |
| |
| void CStringChecker::evalStrcmp(CheckerContext &C, const CallExpr *CE) const { |
| //int strcmp(const char *s1, const char *s2); |
| evalStrcmpCommon(C, CE, /* isBounded = */ false, /* ignoreCase = */ false); |
| } |
| |
| void CStringChecker::evalStrncmp(CheckerContext &C, const CallExpr *CE) const { |
| //int strncmp(const char *s1, const char *s2, size_t n); |
| evalStrcmpCommon(C, CE, /* isBounded = */ true, /* ignoreCase = */ false); |
| } |
| |
| void CStringChecker::evalStrcasecmp(CheckerContext &C, |
| const CallExpr *CE) const { |
| //int strcasecmp(const char *s1, const char *s2); |
| evalStrcmpCommon(C, CE, /* isBounded = */ false, /* ignoreCase = */ true); |
| } |
| |
| void CStringChecker::evalStrncasecmp(CheckerContext &C, |
| const CallExpr *CE) const { |
| //int strncasecmp(const char *s1, const char *s2, size_t n); |
| evalStrcmpCommon(C, CE, /* isBounded = */ true, /* ignoreCase = */ true); |
| } |
| |
| void CStringChecker::evalStrcmpCommon(CheckerContext &C, const CallExpr *CE, |
| bool isBounded, bool ignoreCase) const { |
| CurrentFunctionDescription = "string comparison function"; |
| const GRState *state = C.getState(); |
| |
| // Check that the first string is non-null |
| const Expr *s1 = CE->getArg(0); |
| SVal s1Val = state->getSVal(s1); |
| state = checkNonNull(C, state, s1, s1Val); |
| if (!state) |
| return; |
| |
| // Check that the second string is non-null. |
| const Expr *s2 = CE->getArg(1); |
| SVal s2Val = state->getSVal(s2); |
| state = checkNonNull(C, state, s2, s2Val); |
| if (!state) |
| return; |
| |
| // Get the string length of the first string or give up. |
| SVal s1Length = getCStringLength(C, state, s1, s1Val); |
| if (s1Length.isUndef()) |
| return; |
| |
| // Get the string length of the second string or give up. |
| SVal s2Length = getCStringLength(C, state, s2, s2Val); |
| if (s2Length.isUndef()) |
| return; |
| |
| // If we know the two buffers are the same, we know the result is 0. |
| // First, get the two buffers' addresses. Another checker will have already |
| // made sure they're not undefined. |
| DefinedOrUnknownSVal LV = cast<DefinedOrUnknownSVal>(s1Val); |
| DefinedOrUnknownSVal RV = cast<DefinedOrUnknownSVal>(s2Val); |
| |
| // See if they are the same. |
| SValBuilder &svalBuilder = C.getSValBuilder(); |
| DefinedOrUnknownSVal SameBuf = svalBuilder.evalEQ(state, LV, RV); |
| const GRState *StSameBuf, *StNotSameBuf; |
| llvm::tie(StSameBuf, StNotSameBuf) = state->assume(SameBuf); |
| |
| // If the two arguments might be the same buffer, we know the result is 0, |
| // and we only need to check one size. |
| if (StSameBuf) { |
| StSameBuf = StSameBuf->BindExpr(CE, svalBuilder.makeZeroVal(CE->getType())); |
| C.addTransition(StSameBuf); |
| |
| // If the two arguments are GUARANTEED to be the same, we're done! |
| if (!StNotSameBuf) |
| return; |
| } |
| |
| assert(StNotSameBuf); |
| state = StNotSameBuf; |
| |
| // At this point we can go about comparing the two buffers. |
| // For now, we only do this if they're both known string literals. |
| |
| // Attempt to extract string literals from both expressions. |
| const StringLiteral *s1StrLiteral = getCStringLiteral(C, state, s1, s1Val); |
| const StringLiteral *s2StrLiteral = getCStringLiteral(C, state, s2, s2Val); |
| bool canComputeResult = false; |
| |
| if (s1StrLiteral && s2StrLiteral) { |
| StringRef s1StrRef = s1StrLiteral->getString(); |
| StringRef s2StrRef = s2StrLiteral->getString(); |
| |
| if (isBounded) { |
| // Get the max number of characters to compare. |
| const Expr *lenExpr = CE->getArg(2); |
| SVal lenVal = state->getSVal(lenExpr); |
| |
| // If the length is known, we can get the right substrings. |
| if (const llvm::APSInt *len = svalBuilder.getKnownValue(state, lenVal)) { |
| // Create substrings of each to compare the prefix. |
| s1StrRef = s1StrRef.substr(0, (size_t)len->getZExtValue()); |
| s2StrRef = s2StrRef.substr(0, (size_t)len->getZExtValue()); |
| canComputeResult = true; |
| } |
| } else { |
| // This is a normal, unbounded strcmp. |
| canComputeResult = true; |
| } |
| |
| if (canComputeResult) { |
| // Real strcmp stops at null characters. |
| size_t s1Term = s1StrRef.find('\0'); |
| if (s1Term != StringRef::npos) |
| s1StrRef = s1StrRef.substr(0, s1Term); |
| |
| size_t s2Term = s2StrRef.find('\0'); |
| if (s2Term != StringRef::npos) |
| s2StrRef = s2StrRef.substr(0, s2Term); |
| |
| // Use StringRef's comparison methods to compute the actual result. |
| int result; |
| |
| if (ignoreCase) { |
| // Compare string 1 to string 2 the same way strcasecmp() does. |
| result = s1StrRef.compare_lower(s2StrRef); |
| } else { |
| // Compare string 1 to string 2 the same way strcmp() does. |
| result = s1StrRef.compare(s2StrRef); |
| } |
| |
| // Build the SVal of the comparison and bind the return value. |
| SVal resultVal = svalBuilder.makeIntVal(result, CE->getType()); |
| state = state->BindExpr(CE, resultVal); |
| } |
| } |
| |
| if (!canComputeResult) { |
| // Conjure a symbolic value. It's the best we can do. |
| unsigned Count = C.getNodeBuilder().getCurrentBlockCount(); |
| SVal resultVal = svalBuilder.getConjuredSymbolVal(NULL, CE, Count); |
| state = state->BindExpr(CE, resultVal); |
| } |
| |
| // Record this as a possible path. |
| C.addTransition(state); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // The driver method, and other Checker callbacks. |
| //===----------------------------------------------------------------------===// |
| |
| bool CStringChecker::evalCall(const CallExpr *CE, CheckerContext &C) const { |
| // Get the callee. All the functions we care about are C functions |
| // with simple identifiers. |
| const GRState *state = C.getState(); |
| const Expr *Callee = CE->getCallee(); |
| const FunctionDecl *FD = state->getSVal(Callee).getAsFunctionDecl(); |
| |
| if (!FD) |
| return false; |
| |
| // Get the name of the callee. If it's a builtin, strip off the prefix. |
| IdentifierInfo *II = FD->getIdentifier(); |
| if (!II) // if no identifier, not a simple C function |
| return false; |
| StringRef Name = II->getName(); |
| if (Name.startswith("__builtin_")) |
| Name = Name.substr(10); |
| |
| FnCheck evalFunction = llvm::StringSwitch<FnCheck>(Name) |
| .Cases("memcpy", "__memcpy_chk", &CStringChecker::evalMemcpy) |
| .Cases("mempcpy", "__mempcpy_chk", &CStringChecker::evalMempcpy) |
| .Cases("memcmp", "bcmp", &CStringChecker::evalMemcmp) |
| .Cases("memmove", "__memmove_chk", &CStringChecker::evalMemmove) |
| .Cases("strcpy", "__strcpy_chk", &CStringChecker::evalStrcpy) |
| .Cases("strncpy", "__strncpy_chk", &CStringChecker::evalStrncpy) |
| .Cases("stpcpy", "__stpcpy_chk", &CStringChecker::evalStpcpy) |
| .Cases("strcat", "__strcat_chk", &CStringChecker::evalStrcat) |
| .Cases("strncat", "__strncat_chk", &CStringChecker::evalStrncat) |
| .Case("strlen", &CStringChecker::evalstrLength) |
| .Case("strnlen", &CStringChecker::evalstrnLength) |
| .Case("strcmp", &CStringChecker::evalStrcmp) |
| .Case("strncmp", &CStringChecker::evalStrncmp) |
| .Case("strcasecmp", &CStringChecker::evalStrcasecmp) |
| .Case("strncasecmp", &CStringChecker::evalStrncasecmp) |
| .Case("bcopy", &CStringChecker::evalBcopy) |
| .Default(NULL); |
| |
| // If the callee isn't a string function, let another checker handle it. |
| if (!evalFunction) |
| return false; |
| |
| // Make sure each function sets its own description. |
| // (But don't bother in a release build.) |
| assert(!(CurrentFunctionDescription = NULL)); |
| |
| // Check and evaluate the call. |
| (this->*evalFunction)(C, CE); |
| return true; |
| } |
| |
| void CStringChecker::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const { |
| // Record string length for char a[] = "abc"; |
| const GRState *state = C.getState(); |
| |
| for (DeclStmt::const_decl_iterator I = DS->decl_begin(), E = DS->decl_end(); |
| I != E; ++I) { |
| const VarDecl *D = dyn_cast<VarDecl>(*I); |
| if (!D) |
| continue; |
| |
| // FIXME: Handle array fields of structs. |
| if (!D->getType()->isArrayType()) |
| continue; |
| |
| const Expr *Init = D->getInit(); |
| if (!Init) |
| continue; |
| if (!isa<StringLiteral>(Init)) |
| continue; |
| |
| Loc VarLoc = state->getLValue(D, C.getPredecessor()->getLocationContext()); |
| const MemRegion *MR = VarLoc.getAsRegion(); |
| if (!MR) |
| continue; |
| |
| SVal StrVal = state->getSVal(Init); |
| assert(StrVal.isValid() && "Initializer string is unknown or undefined"); |
| DefinedOrUnknownSVal strLength |
| = cast<DefinedOrUnknownSVal>(getCStringLength(C, state, Init, StrVal)); |
| |
| state = state->set<CStringLength>(MR, strLength); |
| } |
| |
| C.addTransition(state); |
| } |
| |
| bool CStringChecker::wantsRegionChangeUpdate(const GRState *state) const { |
| CStringLength::EntryMap Entries = state->get<CStringLength>(); |
| return !Entries.isEmpty(); |
| } |
| |
| const GRState * |
| CStringChecker::checkRegionChanges(const GRState *state, |
| const StoreManager::InvalidatedSymbols *, |
| const MemRegion * const *Begin, |
| const MemRegion * const *End) const { |
| CStringLength::EntryMap Entries = state->get<CStringLength>(); |
| if (Entries.isEmpty()) |
| return state; |
| |
| llvm::SmallPtrSet<const MemRegion *, 8> Invalidated; |
| llvm::SmallPtrSet<const MemRegion *, 32> SuperRegions; |
| |
| // First build sets for the changed regions and their super-regions. |
| for ( ; Begin != End; ++Begin) { |
| const MemRegion *MR = *Begin; |
| Invalidated.insert(MR); |
| |
| SuperRegions.insert(MR); |
| while (const SubRegion *SR = dyn_cast<SubRegion>(MR)) { |
| MR = SR->getSuperRegion(); |
| SuperRegions.insert(MR); |
| } |
| } |
| |
| CStringLength::EntryMap::Factory &F = state->get_context<CStringLength>(); |
| |
| // Then loop over the entries in the current state. |
| for (CStringLength::EntryMap::iterator I = Entries.begin(), |
| E = Entries.end(); I != E; ++I) { |
| const MemRegion *MR = I.getKey(); |
| |
| // Is this entry for a super-region of a changed region? |
| if (SuperRegions.count(MR)) { |
| Entries = F.remove(Entries, MR); |
| continue; |
| } |
| |
| // Is this entry for a sub-region of a changed region? |
| const MemRegion *Super = MR; |
| while (const SubRegion *SR = dyn_cast<SubRegion>(Super)) { |
| Super = SR->getSuperRegion(); |
| if (Invalidated.count(Super)) { |
| Entries = F.remove(Entries, MR); |
| break; |
| } |
| } |
| } |
| |
| return state->set<CStringLength>(Entries); |
| } |
| |
| void CStringChecker::checkLiveSymbols(const GRState *state, |
| SymbolReaper &SR) const { |
| // Mark all symbols in our string length map as valid. |
| CStringLength::EntryMap Entries = state->get<CStringLength>(); |
| |
| for (CStringLength::EntryMap::iterator I = Entries.begin(), E = Entries.end(); |
| I != E; ++I) { |
| SVal Len = I.getData(); |
| |
| for (SVal::symbol_iterator si = Len.symbol_begin(), se = Len.symbol_end(); |
| si != se; ++si) |
| SR.markInUse(*si); |
| } |
| } |
| |
| void CStringChecker::checkDeadSymbols(SymbolReaper &SR, |
| CheckerContext &C) const { |
| if (!SR.hasDeadSymbols()) |
| return; |
| |
| const GRState *state = C.getState(); |
| CStringLength::EntryMap Entries = state->get<CStringLength>(); |
| if (Entries.isEmpty()) |
| return; |
| |
| CStringLength::EntryMap::Factory &F = state->get_context<CStringLength>(); |
| for (CStringLength::EntryMap::iterator I = Entries.begin(), E = Entries.end(); |
| I != E; ++I) { |
| SVal Len = I.getData(); |
| if (SymbolRef Sym = Len.getAsSymbol()) { |
| if (SR.isDead(Sym)) |
| Entries = F.remove(Entries, I.getKey()); |
| } |
| } |
| |
| state = state->set<CStringLength>(Entries); |
| C.generateNode(state); |
| } |
| |
| void ento::registerCStringChecker(CheckerManager &mgr) { |
| mgr.registerChecker<CStringChecker>(); |
| } |