MallocSizeofChecker.cpp revision 88db6a2daa8bb55fe924773805f42616c8a4f314 
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
25using namespace clang;
26using namespace ento;
27
28namespace {
29
30typedef std::pair<const TypeSourceInfo *, const CallExpr *> TypeCallPair;
31typedef llvm::PointerUnion<const Stmt *, const VarDecl *> ExprParent;
32
33class CastedAllocFinder
34  : public ConstStmtVisitor<CastedAllocFinder, TypeCallPair> {
35  IdentifierInfo *II_malloc, *II_calloc, *II_realloc;
36
37public:
38  struct CallRecord {
39    ExprParent CastedExprParent;
40    const Expr *CastedExpr;
41    const TypeSourceInfo *ExplicitCastType;
42    const CallExpr *AllocCall;
43
44    CallRecord(ExprParent CastedExprParent, const Expr *CastedExpr,
45               const TypeSourceInfo *ExplicitCastType,
46               const CallExpr *AllocCall)
47      : CastedExprParent(CastedExprParent), CastedExpr(CastedExpr),
48        ExplicitCastType(ExplicitCastType), AllocCall(AllocCall) {}
49  };
50
51  typedef std::vector<CallRecord> CallVec;
52  CallVec Calls;
53
54  CastedAllocFinder(ASTContext *Ctx) :
55    II_malloc(&Ctx->Idents.get("malloc")),
56    II_calloc(&Ctx->Idents.get("calloc")),
57    II_realloc(&Ctx->Idents.get("realloc")) {}
58
59  void VisitChild(ExprParent Parent, const Stmt *S) {
60    TypeCallPair AllocCall = Visit(S);
61    if (AllocCall.second && AllocCall.second != S)
62      Calls.push_back(CallRecord(Parent, cast<Expr>(S), AllocCall.first,
63                                 AllocCall.second));
64  }
65
66  void VisitChildren(const Stmt *S) {
67    for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
68         I!=E; ++I)
69      if (const Stmt *child = *I)
70        VisitChild(S, child);
71  }
72
73  TypeCallPair VisitCastExpr(const CastExpr *E) {
74    return Visit(E->getSubExpr());
75  }
76
77  TypeCallPair VisitExplicitCastExpr(const ExplicitCastExpr *E) {
78    return TypeCallPair(E->getTypeInfoAsWritten(),
79                        Visit(E->getSubExpr()).second);
80  }
81
82  TypeCallPair VisitParenExpr(const ParenExpr *E) {
83    return Visit(E->getSubExpr());
84  }
85
86  TypeCallPair VisitStmt(const Stmt *S) {
87    VisitChildren(S);
88    return TypeCallPair();
89  }
90
91  TypeCallPair VisitCallExpr(const CallExpr *E) {
92    VisitChildren(E);
93    const FunctionDecl *FD = E->getDirectCallee();
94    if (FD) {
95      IdentifierInfo *II = FD->getIdentifier();
96      if (II == II_malloc || II == II_calloc || II == II_realloc)
97        return TypeCallPair((const TypeSourceInfo *)0, E);
98    }
99    return TypeCallPair();
100  }
101
102  TypeCallPair VisitDeclStmt(const DeclStmt *S) {
103    for (DeclStmt::const_decl_iterator I = S->decl_begin(), E = S->decl_end();
104         I!=E; ++I)
105      if (const VarDecl *VD = dyn_cast<VarDecl>(*I))
106        if (const Expr *Init = VD->getInit())
107          VisitChild(VD, Init);
108    return TypeCallPair();
109  }
110};
111
112class SizeofFinder : public ConstStmtVisitor<SizeofFinder> {
113public:
114  std::vector<const UnaryExprOrTypeTraitExpr *> Sizeofs;
115
116  void VisitBinMul(const BinaryOperator *E) {
117    Visit(E->getLHS());
118    Visit(E->getRHS());
119  }
120
121  void VisitBinAdd(const BinaryOperator *E) {
122    Visit(E->getLHS());
123    Visit(E->getRHS());
124  }
125
126  void VisitImplicitCastExpr(const ImplicitCastExpr *E) {
127    return Visit(E->getSubExpr());
128  }
129
130  void VisitParenExpr(const ParenExpr *E) {
131    return Visit(E->getSubExpr());
132  }
133
134  void VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E) {
135    if (E->getKind() != UETT_SizeOf)
136      return;
137
138    Sizeofs.push_back(E);
139  }
140};
141
142// Determine if the pointee and sizeof types are compatible.  Here
143// we ignore constness of pointer types.
144static bool typesCompatible(ASTContext &C, QualType A, QualType B) {
145  while (true) {
146    A = A.getCanonicalType();
147    B = B.getCanonicalType();
148
149    if (A.getTypePtr() == B.getTypePtr())
150      return true;
151
152    if (const PointerType *ptrA = A->getAs<PointerType>())
153      if (const PointerType *ptrB = B->getAs<PointerType>()) {
154	A = ptrA->getPointeeType();
155	B = ptrB->getPointeeType();
156	continue;
157      }
158
159    break;
160  }
161
162  return false;
163}
164
165class MallocSizeofChecker : public Checker<check::ASTCodeBody> {
166public:
167  void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
168                        BugReporter &BR) const {
169    AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D);
170    CastedAllocFinder Finder(&BR.getContext());
171    Finder.Visit(D->getBody());
172    for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(),
173         e = Finder.Calls.end(); i != e; ++i) {
174      QualType CastedType = i->CastedExpr->getType();
175      if (!CastedType->isPointerType())
176        continue;
177      QualType PointeeType = CastedType->getAs<PointerType>()->getPointeeType();
178      if (PointeeType->isVoidType())
179        continue;
180
181      for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(),
182           ae = i->AllocCall->arg_end(); ai != ae; ++ai) {
183        if (!(*ai)->getType()->isIntegerType())
184          continue;
185
186        SizeofFinder SFinder;
187        SFinder.Visit(*ai);
188        if (SFinder.Sizeofs.size() != 1)
189          continue;
190
191        QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument();
192        if (!typesCompatible(BR.getContext(), PointeeType, SizeofType)) {
193          const TypeSourceInfo *TSI = 0;
194          if (i->CastedExprParent.is<const VarDecl *>()) {
195            TSI =
196              i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo();
197          } else {
198            TSI = i->ExplicitCastType;
199          }
200
201          SmallString<64> buf;
202          llvm::raw_svector_ostream OS(buf);
203
204          OS << "Result of '"
205             << i->AllocCall->getDirectCallee()->getIdentifier()->getName()
206             << "' is converted to type '"
207             << CastedType.getAsString() << "', whose pointee type '"
208             << PointeeType.getAsString() << "' is incompatible with "
209             << "sizeof operand type '" << SizeofType.getAsString() << "'";
210          llvm::SmallVector<SourceRange, 4> Ranges;
211          Ranges.push_back(i->AllocCall->getCallee()->getSourceRange());
212          Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange());
213          if (TSI)
214            Ranges.push_back(TSI->getTypeLoc().getSourceRange());
215
216          PathDiagnosticLocation L =
217            PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(),
218                                                BR.getSourceManager(), ADC);
219
220          BR.EmitBasicReport(D, "allocator sizeof operand mismatch",
221                             categories::UnixAPI,
222                             OS.str(),
223                             L, Ranges.data(), Ranges.size());
224        }
225      }
226    }
227  }
228};
229
230}
231
232void ento::registerMallocSizeofChecker(CheckerManager &mgr) {
233  mgr.registerChecker<MallocSizeofChecker>();
234}
235