lib/StaticAnalyzer/EntoSA/Checkers/PointerArithChecker.cpp

   1 //=== PointerArithChecker.cpp - Pointer arithmetic 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 PointerArithChecker, a builtin checker that checks for
  11 // pointer arithmetic on locations other than array elements.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "ExprEngineInternalChecks.h"
  16 #include "clang/StaticAnalyzer/BugReporter/BugType.h"
  17 #include "clang/StaticAnalyzer/PathSensitive/CheckerVisitor.h"
  18
  19 using namespace clang;
  20 using namespace ento;
  21
  22 namespace {
  23 class PointerArithChecker
  24   : public CheckerVisitor<PointerArithChecker> {
  25   BuiltinBug *BT;
  26 public:
  27   PointerArithChecker() : BT(0) {}
  28   static void *getTag();
  29   void PreVisitBinaryOperator(CheckerContext &C, const BinaryOperator *B);
  30 };
  31 }
  32
  33 void *PointerArithChecker::getTag() {
  34   static int x;
  35   return &x;
  36 }
  37
  38 void PointerArithChecker::PreVisitBinaryOperator(CheckerContext &C,
  39                                                  const BinaryOperator *B) {
  40   if (B->getOpcode() != BO_Sub && B->getOpcode() != BO_Add)
  41     return;
  42
  43   const GRState *state = C.getState();
  44   SVal LV = state->getSVal(B->getLHS());
  45   SVal RV = state->getSVal(B->getRHS());
  46
  47   const MemRegion *LR = LV.getAsRegion();
  48
  49   if (!LR || !RV.isConstant())
  50     return;
  51
  52   // If pointer arithmetic is done on variables of non-array type, this often
  53   // means behavior rely on memory organization, which is dangerous.
  54   if (isa<VarRegion>(LR) || isa<CodeTextRegion>(LR) ||
  55       isa<CompoundLiteralRegion>(LR)) {
  56
  57     if (ExplodedNode *N = C.generateNode()) {
  58       if (!BT)
  59         BT = new BuiltinBug("Dangerous pointer arithmetic",
  60                             "Pointer arithmetic done on non-array variables "
  61                             "means reliance on memory layout, which is "
  62                             "dangerous.");
  63       RangedBugReport *R = new RangedBugReport(*BT, BT->getDescription(), N);
  64       R->addRange(B->getSourceRange());
  65       C.EmitReport(R);
  66     }
  67   }
  68 }
  69
  70 void ento::RegisterPointerArithChecker(ExprEngine &Eng) {
  71   Eng.registerCheck(new PointerArithChecker());
  72 }