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/AST/StmtVisitor.h"
18 #include "clang/AST/TypeLoc.h"
19 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
20 #include "clang/StaticAnalyzer/Core/Checker.h"
21 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
22 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
23 #include "llvm/ADT/SmallString.h"
24 #include "llvm/Support/raw_ostream.h"
25
26 using namespace clang;
27 using namespace ento;
28
29 namespace {
30
31 typedef std::pair<const TypeSourceInfo *, const CallExpr *> TypeCallPair;
32 typedef llvm::PointerUnion<const Stmt *, const VarDecl *> ExprParent;
33
34 class CastedAllocFinder
35 : public ConstStmtVisitor<CastedAllocFinder, TypeCallPair> {
36 IdentifierInfo *II_malloc, *II_calloc, *II_realloc;
37
38 public:
39 struct CallRecord {
40 ExprParent CastedExprParent;
41 const Expr *CastedExpr;
42 const TypeSourceInfo *ExplicitCastType;
43 const CallExpr *AllocCall;
44
CallRecord__anon4d425d760111::CastedAllocFinder::CallRecord45 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
CastedAllocFinder(ASTContext * Ctx)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
VisitChild(ExprParent Parent,const Stmt * S)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
VisitChildren(const Stmt * S)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
VisitCastExpr(const CastExpr * E)74 TypeCallPair VisitCastExpr(const CastExpr *E) {
75 return Visit(E->getSubExpr());
76 }
77
VisitExplicitCastExpr(const ExplicitCastExpr * E)78 TypeCallPair VisitExplicitCastExpr(const ExplicitCastExpr *E) {
79 return TypeCallPair(E->getTypeInfoAsWritten(),
80 Visit(E->getSubExpr()).second);
81 }
82
VisitParenExpr(const ParenExpr * E)83 TypeCallPair VisitParenExpr(const ParenExpr *E) {
84 return Visit(E->getSubExpr());
85 }
86
VisitStmt(const Stmt * S)87 TypeCallPair VisitStmt(const Stmt *S) {
88 VisitChildren(S);
89 return TypeCallPair();
90 }
91
VisitCallExpr(const CallExpr * E)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 *)nullptr, E);
99 }
100 return TypeCallPair();
101 }
102
VisitDeclStmt(const DeclStmt * S)103 TypeCallPair VisitDeclStmt(const DeclStmt *S) {
104 for (const auto *I : S->decls())
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
112 class SizeofFinder : public ConstStmtVisitor<SizeofFinder> {
113 public:
114 std::vector<const UnaryExprOrTypeTraitExpr *> Sizeofs;
115
VisitBinMul(const BinaryOperator * E)116 void VisitBinMul(const BinaryOperator *E) {
117 Visit(E->getLHS());
118 Visit(E->getRHS());
119 }
120
VisitImplicitCastExpr(const ImplicitCastExpr * E)121 void VisitImplicitCastExpr(const ImplicitCastExpr *E) {
122 return Visit(E->getSubExpr());
123 }
124
VisitParenExpr(const ParenExpr * E)125 void VisitParenExpr(const ParenExpr *E) {
126 return Visit(E->getSubExpr());
127 }
128
VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr * E)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.
typesCompatible(ASTContext & C,QualType A,QualType B)139 static bool typesCompatible(ASTContext &C, QualType A, QualType B) {
140 // sizeof(void*) is compatible with any other pointer.
141 if (B->isVoidPointerType() && A->getAs<PointerType>())
142 return true;
143
144 while (true) {
145 A = A.getCanonicalType();
146 B = B.getCanonicalType();
147
148 if (A.getTypePtr() == B.getTypePtr())
149 return true;
150
151 if (const PointerType *ptrA = A->getAs<PointerType>())
152 if (const PointerType *ptrB = B->getAs<PointerType>()) {
153 A = ptrA->getPointeeType();
154 B = ptrB->getPointeeType();
155 continue;
156 }
157
158 break;
159 }
160
161 return false;
162 }
163
compatibleWithArrayType(ASTContext & C,QualType PT,QualType T)164 static bool compatibleWithArrayType(ASTContext &C, QualType PT, QualType T) {
165 // Ex: 'int a[10][2]' is compatible with 'int', 'int[2]', 'int[10][2]'.
166 while (const ArrayType *AT = T->getAsArrayTypeUnsafe()) {
167 QualType ElemType = AT->getElementType();
168 if (typesCompatible(C, PT, AT->getElementType()))
169 return true;
170 T = ElemType;
171 }
172
173 return false;
174 }
175
176 class MallocSizeofChecker : public Checker<check::ASTCodeBody> {
177 public:
checkASTCodeBody(const Decl * D,AnalysisManager & mgr,BugReporter & BR) const178 void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
179 BugReporter &BR) const {
180 AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D);
181 CastedAllocFinder Finder(&BR.getContext());
182 Finder.Visit(D->getBody());
183 for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(),
184 e = Finder.Calls.end(); i != e; ++i) {
185 QualType CastedType = i->CastedExpr->getType();
186 if (!CastedType->isPointerType())
187 continue;
188 QualType PointeeType = CastedType->getAs<PointerType>()->getPointeeType();
189 if (PointeeType->isVoidType())
190 continue;
191
192 for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(),
193 ae = i->AllocCall->arg_end(); ai != ae; ++ai) {
194 if (!(*ai)->getType()->isIntegralOrUnscopedEnumerationType())
195 continue;
196
197 SizeofFinder SFinder;
198 SFinder.Visit(*ai);
199 if (SFinder.Sizeofs.size() != 1)
200 continue;
201
202 QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument();
203
204 if (typesCompatible(BR.getContext(), PointeeType, SizeofType))
205 continue;
206
207 // If the argument to sizeof is an array, the result could be a
208 // pointer to any array element.
209 if (compatibleWithArrayType(BR.getContext(), PointeeType, SizeofType))
210 continue;
211
212 const TypeSourceInfo *TSI = nullptr;
213 if (i->CastedExprParent.is<const VarDecl *>()) {
214 TSI =
215 i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo();
216 } else {
217 TSI = i->ExplicitCastType;
218 }
219
220 SmallString<64> buf;
221 llvm::raw_svector_ostream OS(buf);
222
223 OS << "Result of ";
224 const FunctionDecl *Callee = i->AllocCall->getDirectCallee();
225 if (Callee && Callee->getIdentifier())
226 OS << '\'' << Callee->getIdentifier()->getName() << '\'';
227 else
228 OS << "call";
229 OS << " is converted to a pointer of type '"
230 << PointeeType.getAsString() << "', which is incompatible with "
231 << "sizeof operand type '" << SizeofType.getAsString() << "'";
232 SmallVector<SourceRange, 4> Ranges;
233 Ranges.push_back(i->AllocCall->getCallee()->getSourceRange());
234 Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange());
235 if (TSI)
236 Ranges.push_back(TSI->getTypeLoc().getSourceRange());
237
238 PathDiagnosticLocation L =
239 PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(),
240 BR.getSourceManager(), ADC);
241
242 BR.EmitBasicReport(D, this, "Allocator sizeof operand mismatch",
243 categories::UnixAPI, OS.str(), L, Ranges);
244 }
245 }
246 }
247 };
248
249 }
250
registerMallocSizeofChecker(CheckerManager & mgr)251 void ento::registerMallocSizeofChecker(CheckerManager &mgr) {
252 mgr.registerChecker<MallocSizeofChecker>();
253 }
254