PointerArithChecker.cpp revision 18c66fdc3c4008d335885695fe36fb5353c5f672 
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 "ClangSACheckers.h"
16#include "clang/StaticAnalyzer/Core/Checker.h"
17#include "clang/StaticAnalyzer/Core/CheckerManager.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
20
21using namespace clang;
22using namespace ento;
23
24namespace {
25class PointerArithChecker
26  : public Checker< check::PreStmt<BinaryOperator> > {
27  mutable llvm::OwningPtr<BuiltinBug> BT;
28
29public:
30  void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
31};
32}
33
34void PointerArithChecker::checkPreStmt(const BinaryOperator *B,
35                                       CheckerContext &C) const {
36  if (B->getOpcode() != BO_Sub && B->getOpcode() != BO_Add)
37    return;
38
39  const ProgramState *state = C.getState();
40  SVal LV = state->getSVal(B->getLHS());
41  SVal RV = state->getSVal(B->getRHS());
42
43  const MemRegion *LR = LV.getAsRegion();
44
45  if (!LR || !RV.isConstant())
46    return;
47
48  // If pointer arithmetic is done on variables of non-array type, this often
49  // means behavior rely on memory organization, which is dangerous.
50  if (isa<VarRegion>(LR) || isa<CodeTextRegion>(LR) ||
51      isa<CompoundLiteralRegion>(LR)) {
52
53    if (ExplodedNode *N = C.generateNode()) {
54      if (!BT)
55        BT.reset(new BuiltinBug("Dangerous pointer arithmetic",
56                            "Pointer arithmetic done on non-array variables "
57                            "means reliance on memory layout, which is "
58                            "dangerous."));
59      RangedBugReport *R = new RangedBugReport(*BT, BT->getDescription(), N);
60      R->addRange(B->getSourceRange());
61      C.EmitReport(R);
62    }
63  }
64}
65
66void ento::registerPointerArithChecker(CheckerManager &mgr) {
67  mgr.registerChecker<PointerArithChecker>();
68}
69