CastSizeChecker.cpp revision e172e8b9e7fc67d7d03589af7e92fe777afcf33a 
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 "ClangSACheckers.h"
15#include "clang/StaticAnalyzer/Core/Checker.h"
16#include "clang/StaticAnalyzer/Core/CheckerManager.h"
17#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
18#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
19#include "clang/AST/CharUnits.h"
20
21using namespace clang;
22using namespace ento;
23
24namespace {
25class CastSizeChecker : public Checker< check::PreStmt<CastExpr> > {
26  mutable llvm::OwningPtr<BuiltinBug> BT;
27public:
28  void checkPreStmt(const CastExpr *CE, CheckerContext &C) const;
29};
30}
31
32void CastSizeChecker::checkPreStmt(const CastExpr *CE,CheckerContext &C) const {
33  const Expr *E = CE->getSubExpr();
34  ASTContext &Ctx = C.getASTContext();
35  QualType ToTy = Ctx.getCanonicalType(CE->getType());
36  const PointerType *ToPTy = dyn_cast<PointerType>(ToTy.getTypePtr());
37
38  if (!ToPTy)
39    return;
40
41  QualType ToPointeeTy = ToPTy->getPointeeType();
42
43  // Only perform the check if 'ToPointeeTy' is a complete type.
44  if (ToPointeeTy->isIncompleteType())
45    return;
46
47  const ProgramState *state = C.getState();
48  const MemRegion *R = state->getSVal(E).getAsRegion();
49  if (R == 0)
50    return;
51
52  const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
53  if (SR == 0)
54    return;
55
56  SValBuilder &svalBuilder = C.getSValBuilder();
57  SVal extent = SR->getExtent(svalBuilder);
58  const llvm::APSInt *extentInt = svalBuilder.getKnownValue(state, extent);
59  if (!extentInt)
60    return;
61
62  CharUnits regionSize = CharUnits::fromQuantity(extentInt->getSExtValue());
63  CharUnits typeSize = C.getASTContext().getTypeSizeInChars(ToPointeeTy);
64
65  // Ignore void, and a few other un-sizeable types.
66  if (typeSize.isZero())
67    return;
68
69  if (regionSize % typeSize != 0) {
70    if (ExplodedNode *errorNode = C.generateSink()) {
71      if (!BT)
72        BT.reset(new BuiltinBug("Cast region with wrong size.",
73                            "Cast a region whose size is not a multiple of the"
74                            " destination type size."));
75      BugReport *R = new BugReport(*BT, BT->getDescription(),
76                                               errorNode);
77      R->addRange(CE->getSourceRange());
78      C.EmitReport(R);
79    }
80  }
81}
82
83
84void ento::registerCastSizeChecker(CheckerManager &mgr) {
85  mgr.registerChecker<CastSizeChecker>();
86}
87