1 //== ArrayBoundChecker.cpp ------------------------------*- C++ -*--==// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file defines ArrayBoundChecker, which is a path-sensitive check 11 // which looks for an out-of-bound array element access. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "ClangSACheckers.h" 16 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 17 #include "clang/StaticAnalyzer/Core/Checker.h" 18 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 20 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 21 22 using namespace clang; 23 using namespace ento; 24 25 namespace { 26 class ArrayBoundChecker : 27 public Checker<check::Location> { 28 mutable OwningPtr<BuiltinBug> BT; 29 public: 30 void checkLocation(SVal l, bool isLoad, const Stmt* S, 31 CheckerContext &C) const; 32 }; 33 } 34 35 void ArrayBoundChecker::checkLocation(SVal l, bool isLoad, const Stmt* LoadS, 36 CheckerContext &C) const { 37 // Check for out of bound array element access. 38 const MemRegion *R = l.getAsRegion(); 39 if (!R) 40 return; 41 42 const ElementRegion *ER = dyn_cast<ElementRegion>(R); 43 if (!ER) 44 return; 45 46 // Get the index of the accessed element. 47 DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>(); 48 49 // Zero index is always in bound, this also passes ElementRegions created for 50 // pointer casts. 51 if (Idx.isZeroConstant()) 52 return; 53 54 ProgramStateRef state = C.getState(); 55 56 // Get the size of the array. 57 DefinedOrUnknownSVal NumElements 58 = C.getStoreManager().getSizeInElements(state, ER->getSuperRegion(), 59 ER->getValueType()); 60 61 ProgramStateRef StInBound = state->assumeInBound(Idx, NumElements, true); 62 ProgramStateRef StOutBound = state->assumeInBound(Idx, NumElements, false); 63 if (StOutBound && !StInBound) { 64 ExplodedNode *N = C.generateSink(StOutBound); 65 if (!N) 66 return; 67 68 if (!BT) 69 BT.reset(new BuiltinBug("Out-of-bound array access", 70 "Access out-of-bound array element (buffer overflow)")); 71 72 // FIXME: It would be nice to eventually make this diagnostic more clear, 73 // e.g., by referencing the original declaration or by saying *why* this 74 // reference is outside the range. 75 76 // Generate a report for this bug. 77 BugReport *report = 78 new BugReport(*BT, BT->getDescription(), N); 79 80 report->addRange(LoadS->getSourceRange()); 81 C.emitReport(report); 82 return; 83 } 84 85 // Array bound check succeeded. From this point forward the array bound 86 // should always succeed. 87 C.addTransition(StInBound); 88 } 89 90 void ento::registerArrayBoundChecker(CheckerManager &mgr) { 91 mgr.registerChecker<ArrayBoundChecker>(); 92 } 93
