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/AST/CharUnits.h"
16 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
17 #include "clang/StaticAnalyzer/Core/Checker.h"
18 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20 
21 using namespace clang;
22 using namespace ento;
23 
24 namespace {
25 class CastSizeChecker : public Checker< check::PreStmt<CastExpr> > {
26   mutable OwningPtr<BuiltinBug> BT;
27 public:
28   void checkPreStmt(const CastExpr *CE, CheckerContext &C) const;
29 };
30 }
31 
32 void 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   ProgramStateRef state = C.getState();
48   const MemRegion *R = state->getSVal(E, C.getLocationContext()).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 
84 void ento::registerCastSizeChecker(CheckerManager &mgr) {
85   mgr.registerChecker<CastSizeChecker>();
86 }
87