MallocSizeofChecker.cpp revision a93d0f280693b8418bc88cf7a8c93325f7fcf4c6 
1// MallocSizeofChecker.cpp - Check for dubious malloc arguments ---*- 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// Reports inconsistencies between the casted type of the return value of a
11// malloc/calloc/realloc call and the operand of any sizeof expressions
12// contained within its argument(s).
13//
14//===----------------------------------------------------------------------===//
15
16#include "ClangSACheckers.h"
17#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
18#include "clang/StaticAnalyzer/Core/Checker.h"
19#include "clang/StaticAnalyzer/Core/CheckerManager.h"
20#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
21#include "clang/AST/StmtVisitor.h"
22#include "clang/AST/TypeLoc.h"
23#include "llvm/ADT/SmallString.h"
24#include "llvm/Support/raw_ostream.h"
25
26using namespace clang;
27using namespace ento;
28
29namespace {
30
31typedef std::pair<const TypeSourceInfo *, const CallExpr *> TypeCallPair;
32typedef llvm::PointerUnion<const Stmt *, const VarDecl *> ExprParent;
33
34class CastedAllocFinder
35  : public ConstStmtVisitor<CastedAllocFinder, TypeCallPair> {
36  IdentifierInfo *II_malloc, *II_calloc, *II_realloc;
37
38public:
39  struct CallRecord {
40    ExprParent CastedExprParent;
41    const Expr *CastedExpr;
42    const TypeSourceInfo *ExplicitCastType;
43    const CallExpr *AllocCall;
44
45    CallRecord(ExprParent CastedExprParent, const Expr *CastedExpr,
46               const TypeSourceInfo *ExplicitCastType,
47               const CallExpr *AllocCall)
48      : CastedExprParent(CastedExprParent), CastedExpr(CastedExpr),
49        ExplicitCastType(ExplicitCastType), AllocCall(AllocCall) {}
50  };
51
52  typedef std::vector<CallRecord> CallVec;
53  CallVec Calls;
54
55  CastedAllocFinder(ASTContext *Ctx) :
56    II_malloc(&Ctx->Idents.get("malloc")),
57    II_calloc(&Ctx->Idents.get("calloc")),
58    II_realloc(&Ctx->Idents.get("realloc")) {}
59
60  void VisitChild(ExprParent Parent, const Stmt *S) {
61    TypeCallPair AllocCall = Visit(S);
62    if (AllocCall.second && AllocCall.second != S)
63      Calls.push_back(CallRecord(Parent, cast<Expr>(S), AllocCall.first,
64                                 AllocCall.second));
65  }
66
67  void VisitChildren(const Stmt *S) {
68    for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
69         I!=E; ++I)
70      if (const Stmt *child = *I)
71        VisitChild(S, child);
72  }
73
74  TypeCallPair VisitCastExpr(const CastExpr *E) {
75    return Visit(E->getSubExpr());
76  }
77
78  TypeCallPair VisitExplicitCastExpr(const ExplicitCastExpr *E) {
79    return TypeCallPair(E->getTypeInfoAsWritten(),
80                        Visit(E->getSubExpr()).second);
81  }
82
83  TypeCallPair VisitParenExpr(const ParenExpr *E) {
84    return Visit(E->getSubExpr());
85  }
86
87  TypeCallPair VisitStmt(const Stmt *S) {
88    VisitChildren(S);
89    return TypeCallPair();
90  }
91
92  TypeCallPair VisitCallExpr(const CallExpr *E) {
93    VisitChildren(E);
94    const FunctionDecl *FD = E->getDirectCallee();
95    if (FD) {
96      IdentifierInfo *II = FD->getIdentifier();
97      if (II == II_malloc || II == II_calloc || II == II_realloc)
98        return TypeCallPair((const TypeSourceInfo *)0, E);
99    }
100    return TypeCallPair();
101  }
102
103  TypeCallPair VisitDeclStmt(const DeclStmt *S) {
104    for (DeclStmt::const_decl_iterator I = S->decl_begin(), E = S->decl_end();
105         I!=E; ++I)
106      if (const VarDecl *VD = dyn_cast<VarDecl>(*I))
107        if (const Expr *Init = VD->getInit())
108          VisitChild(VD, Init);
109    return TypeCallPair();
110  }
111};
112
113class SizeofFinder : public ConstStmtVisitor<SizeofFinder> {
114public:
115  std::vector<const UnaryExprOrTypeTraitExpr *> Sizeofs;
116
117  void VisitBinMul(const BinaryOperator *E) {
118    Visit(E->getLHS());
119    Visit(E->getRHS());
120  }
121
122  void VisitImplicitCastExpr(const ImplicitCastExpr *E) {
123    return Visit(E->getSubExpr());
124  }
125
126  void VisitParenExpr(const ParenExpr *E) {
127    return Visit(E->getSubExpr());
128  }
129
130  void VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E) {
131    if (E->getKind() != UETT_SizeOf)
132      return;
133
134    Sizeofs.push_back(E);
135  }
136};
137
138// Determine if the pointee and sizeof types are compatible.  Here
139// we ignore constness of pointer types.
140static bool typesCompatible(ASTContext &C, QualType A, QualType B) {
141  while (true) {
142    A = A.getCanonicalType();
143    B = B.getCanonicalType();
144
145    if (A.getTypePtr() == B.getTypePtr())
146      return true;
147
148    if (const PointerType *ptrA = A->getAs<PointerType>())
149      if (const PointerType *ptrB = B->getAs<PointerType>()) {
150        A = ptrA->getPointeeType();
151        B = ptrB->getPointeeType();
152        continue;
153      }
154
155    break;
156  }
157
158  return false;
159}
160
161static bool compatibleWithArrayType(ASTContext &C, QualType PT, QualType T) {
162  // Ex: 'int a[10][2]' is compatible with 'int', 'int[2]', 'int[10][2]'.
163  while (const ArrayType *AT = T->getAsArrayTypeUnsafe()) {
164    QualType ElemType = AT->getElementType();
165    if (typesCompatible(C, PT, AT->getElementType()))
166      return true;
167    T = ElemType;
168  }
169
170  return false;
171}
172
173class MallocSizeofChecker : public Checker<check::ASTCodeBody> {
174public:
175  void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
176                        BugReporter &BR) const {
177    AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D);
178    CastedAllocFinder Finder(&BR.getContext());
179    Finder.Visit(D->getBody());
180    for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(),
181         e = Finder.Calls.end(); i != e; ++i) {
182      QualType CastedType = i->CastedExpr->getType();
183      if (!CastedType->isPointerType())
184        continue;
185      QualType PointeeType = CastedType->getAs<PointerType>()->getPointeeType();
186      if (PointeeType->isVoidType())
187        continue;
188
189      for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(),
190           ae = i->AllocCall->arg_end(); ai != ae; ++ai) {
191        if (!(*ai)->getType()->isIntegerType())
192          continue;
193
194        SizeofFinder SFinder;
195        SFinder.Visit(*ai);
196        if (SFinder.Sizeofs.size() != 1)
197          continue;
198
199        QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument();
200
201        if (typesCompatible(BR.getContext(), PointeeType, SizeofType))
202          continue;
203
204        // If the argument to sizeof is an array, the result could be a
205        // pointer to any array element.
206        if (compatibleWithArrayType(BR.getContext(), PointeeType, SizeofType))
207          continue;
208
209        const TypeSourceInfo *TSI = 0;
210        if (i->CastedExprParent.is<const VarDecl *>()) {
211          TSI =
212              i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo();
213        } else {
214          TSI = i->ExplicitCastType;
215        }
216
217        SmallString<64> buf;
218        llvm::raw_svector_ostream OS(buf);
219
220        OS << "Result of ";
221        const FunctionDecl *Callee = i->AllocCall->getDirectCallee();
222        if (Callee && Callee->getIdentifier())
223          OS << '\'' << Callee->getIdentifier()->getName() << '\'';
224        else
225          OS << "call";
226        OS << " is converted to a pointer of type '"
227            << PointeeType.getAsString() << "', which is incompatible with "
228            << "sizeof operand type '" << SizeofType.getAsString() << "'";
229        llvm::SmallVector<SourceRange, 4> Ranges;
230        Ranges.push_back(i->AllocCall->getCallee()->getSourceRange());
231        Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange());
232        if (TSI)
233          Ranges.push_back(TSI->getTypeLoc().getSourceRange());
234
235        PathDiagnosticLocation L =
236            PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(),
237                BR.getSourceManager(), ADC);
238
239        BR.EmitBasicReport(D, "Allocator sizeof operand mismatch",
240            categories::UnixAPI,
241            OS.str(),
242            L, Ranges.data(), Ranges.size());
243      }
244    }
245  }
246};
247
248}
249
250void ento::registerMallocSizeofChecker(CheckerManager &mgr) {
251  mgr.registerChecker<MallocSizeofChecker>();
252}
253