1 //=== PointerSubChecker.cpp - Pointer subtraction checker ------*- C++ -*--===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This files defines PointerSubChecker, a builtin checker that checks for 11 // pointer subtractions on two pointers pointing to different memory chunks. 12 // This check corresponds to CWE-469. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "ClangSACheckers.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/BugReporter/BugType.h" 21 22 using namespace clang; 23 using namespace ento; 24 25 namespace { 26 class PointerSubChecker 27 : public Checker< check::PreStmt<BinaryOperator> > { 28 mutable llvm::OwningPtr<BuiltinBug> BT; 29 30 public: 31 void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const; 32 }; 33 } 34 35 void PointerSubChecker::checkPreStmt(const BinaryOperator *B, 36 CheckerContext &C) const { 37 // When doing pointer subtraction, if the two pointers do not point to the 38 // same memory chunk, emit a warning. 39 if (B->getOpcode() != BO_Sub) 40 return; 41 42 const ProgramState *state = C.getState(); 43 SVal LV = state->getSVal(B->getLHS()); 44 SVal RV = state->getSVal(B->getRHS()); 45 46 const MemRegion *LR = LV.getAsRegion(); 47 const MemRegion *RR = RV.getAsRegion(); 48 49 if (!(LR && RR)) 50 return; 51 52 const MemRegion *BaseLR = LR->getBaseRegion(); 53 const MemRegion *BaseRR = RR->getBaseRegion(); 54 55 if (BaseLR == BaseRR) 56 return; 57 58 // Allow arithmetic on different symbolic regions. 59 if (isa<SymbolicRegion>(BaseLR) || isa<SymbolicRegion>(BaseRR)) 60 return; 61 62 if (ExplodedNode *N = C.generateNode()) { 63 if (!BT) 64 BT.reset(new BuiltinBug("Pointer subtraction", 65 "Subtraction of two pointers that do not point to " 66 "the same memory chunk may cause incorrect result.")); 67 BugReport *R = new BugReport(*BT, BT->getDescription(), N); 68 R->addRange(B->getSourceRange()); 69 C.EmitReport(R); 70 } 71 } 72 73 void ento::registerPointerSubChecker(CheckerManager &mgr) { 74 mgr.registerChecker<PointerSubChecker>(); 75 } 76
