MallocSizeofChecker.cpp revision d21c96409fee1d09331d9218bd673d0df7352874 
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 VisitImplicitCastExpr(const ImplicitCastExpr *E) {
122    return Visit(E->getSubExpr());
123  }
124
125  void VisitParenExpr(const ParenExpr *E) {
126    return Visit(E->getSubExpr());
127  }
128
129  void VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E) {
130    if (E->getKind() != UETT_SizeOf)
131      return;
132
133    Sizeofs.push_back(E);
134  }
135};
136
137// Determine if the pointee and sizeof types are compatible.  Here
138// we ignore constness of pointer types.
139static bool typesCompatible(ASTContext &C, QualType A, QualType B) {
140  while (true) {
141    A = A.getCanonicalType();
142    B = B.getCanonicalType();
143
144    if (A.getTypePtr() == B.getTypePtr())
145      return true;
146
147    if (const PointerType *ptrA = A->getAs<PointerType>())
148      if (const PointerType *ptrB = B->getAs<PointerType>()) {
149        A = ptrA->getPointeeType();
150        B = ptrB->getPointeeType();
151        continue;
152      }
153
154    break;
155  }
156
157  return false;
158}
159
160class MallocSizeofChecker : public Checker<check::ASTCodeBody> {
161public:
162  void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
163                        BugReporter &BR) const {
164    AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D);
165    CastedAllocFinder Finder(&BR.getContext());
166    Finder.Visit(D->getBody());
167    for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(),
168         e = Finder.Calls.end(); i != e; ++i) {
169      QualType CastedType = i->CastedExpr->getType();
170      if (!CastedType->isPointerType())
171        continue;
172      QualType PointeeType = CastedType->getAs<PointerType>()->getPointeeType();
173      if (PointeeType->isVoidType())
174        continue;
175
176      for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(),
177           ae = i->AllocCall->arg_end(); ai != ae; ++ai) {
178        if (!(*ai)->getType()->isIntegerType())
179          continue;
180
181        SizeofFinder SFinder;
182        SFinder.Visit(*ai);
183        if (SFinder.Sizeofs.size() != 1)
184          continue;
185
186        QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument();
187        if (!typesCompatible(BR.getContext(), PointeeType, SizeofType)) {
188          const TypeSourceInfo *TSI = 0;
189          if (i->CastedExprParent.is<const VarDecl *>()) {
190            TSI =
191              i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo();
192          } else {
193            TSI = i->ExplicitCastType;
194          }
195
196          SmallString<64> buf;
197          llvm::raw_svector_ostream OS(buf);
198
199          OS << "Result of ";
200          const FunctionDecl *Callee = i->AllocCall->getDirectCallee();
201          if (Callee && Callee->getIdentifier())
202            OS << '\'' << Callee->getIdentifier()->getName() << '\'';
203          else
204            OS << "call";
205          OS << " is converted to a pointer of type '"
206             << PointeeType.getAsString() << "', which is incompatible with "
207             << "sizeof operand type '" << SizeofType.getAsString() << "'";
208          llvm::SmallVector<SourceRange, 4> Ranges;
209          Ranges.push_back(i->AllocCall->getCallee()->getSourceRange());
210          Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange());
211          if (TSI)
212            Ranges.push_back(TSI->getTypeLoc().getSourceRange());
213
214          PathDiagnosticLocation L =
215            PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(),
216                                                BR.getSourceManager(), ADC);
217
218          BR.EmitBasicReport(D, "Allocator sizeof operand mismatch",
219                             categories::UnixAPI,
220                             OS.str(),
221                             L, Ranges.data(), Ranges.size());
222        }
223      }
224    }
225  }
226};
227
228}
229
230void ento::registerMallocSizeofChecker(CheckerManager &mgr) {
231  mgr.registerChecker<MallocSizeofChecker>();
232}
233