PointerArithChecker.cpp revision 5eca482fe895ea57bc82410222e6426c09e63284 
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  const LocationContext *LCtx = C.getLocationContext();
41  SVal LV = state->getSVal(B->getLHS(), LCtx);
42  SVal RV = state->getSVal(B->getRHS(), LCtx);
43
44  const MemRegion *LR = LV.getAsRegion();
45
46  if (!LR || !RV.isConstant())
47    return;
48
49  // If pointer arithmetic is done on variables of non-array type, this often
50  // means behavior rely on memory organization, which is dangerous.
51  if (isa<VarRegion>(LR) || isa<CodeTextRegion>(LR) ||
52      isa<CompoundLiteralRegion>(LR)) {
53
54    if (ExplodedNode *N = C.addTransition()) {
55      if (!BT)
56        BT.reset(new BuiltinBug("Dangerous pointer arithmetic",
57                            "Pointer arithmetic done on non-array variables "
58                            "means reliance on memory layout, which is "
59                            "dangerous."));
60      BugReport *R = new BugReport(*BT, BT->getDescription(), N);
61      R->addRange(B->getSourceRange());
62      C.EmitReport(R);
63    }
64  }
65}
66
67void ento::registerPointerArithChecker(CheckerManager &mgr) {
68  mgr.registerChecker<PointerArithChecker>();
69}
70