CastSizeChecker.cpp revision 04291a7c76e16a2dc5433c80c3d13c826bf372dc 
1//=== CastSizeChecker.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// CastSizeChecker checks when casting a malloc'ed symbolic region to type T,
11// whether the size of the symbolic region is a multiple of the size of T.
12//
13//===----------------------------------------------------------------------===//
14#include "clang/AST/CharUnits.h"
15#include "clang/StaticAnalyzer/BugReporter/BugType.h"
16#include "clang/StaticAnalyzer/PathSensitive/CheckerVisitor.h"
17#include "InternalChecks.h"
18
19using namespace clang;
20using namespace ento;
21
22namespace {
23class CastSizeChecker : public CheckerVisitor<CastSizeChecker> {
24  BuiltinBug *BT;
25public:
26  CastSizeChecker() : BT(0) {}
27  static void *getTag();
28  void PreVisitCastExpr(CheckerContext &C, const CastExpr *B);
29};
30}
31
32void *CastSizeChecker::getTag() {
33  static int x;
34  return &x;
35}
36
37void CastSizeChecker::PreVisitCastExpr(CheckerContext &C, const CastExpr *CE) {
38  const Expr *E = CE->getSubExpr();
39  ASTContext &Ctx = C.getASTContext();
40  QualType ToTy = Ctx.getCanonicalType(CE->getType());
41  const PointerType *ToPTy = dyn_cast<PointerType>(ToTy.getTypePtr());
42
43  if (!ToPTy)
44    return;
45
46  QualType ToPointeeTy = ToPTy->getPointeeType();
47
48  // Only perform the check if 'ToPointeeTy' is a complete type.
49  if (ToPointeeTy->isIncompleteType())
50    return;
51
52  const GRState *state = C.getState();
53  const MemRegion *R = state->getSVal(E).getAsRegion();
54  if (R == 0)
55    return;
56
57  const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
58  if (SR == 0)
59    return;
60
61  SValBuilder &svalBuilder = C.getSValBuilder();
62  SVal extent = SR->getExtent(svalBuilder);
63  const llvm::APSInt *extentInt = svalBuilder.getKnownValue(state, extent);
64  if (!extentInt)
65    return;
66
67  CharUnits regionSize = CharUnits::fromQuantity(extentInt->getSExtValue());
68  CharUnits typeSize = C.getASTContext().getTypeSizeInChars(ToPointeeTy);
69
70  // Ignore void, and a few other un-sizeable types.
71  if (typeSize.isZero())
72    return;
73
74  if (regionSize % typeSize != 0) {
75    if (ExplodedNode *errorNode = C.generateSink()) {
76      if (!BT)
77        BT = new BuiltinBug("Cast region with wrong size.",
78                            "Cast a region whose size is not a multiple of the"
79                            " destination type size.");
80      RangedBugReport *R = new RangedBugReport(*BT, BT->getDescription(),
81                                               errorNode);
82      R->addRange(CE->getSourceRange());
83      C.EmitReport(R);
84    }
85  }
86}
87
88
89void ento::RegisterCastSizeChecker(ExprEngine &Eng) {
90  Eng.registerCheck(new CastSizeChecker());
91}
92