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
25 using namespace clang;
26 using namespace ento;
27
28 namespace {
29
30 typedef std::pair<const TypeSourceInfo *, const CallExpr *> TypeCallPair;
31 typedef llvm::PointerUnion<const Stmt *, const VarDecl *> ExprParent;
32
33 class CastedAllocFinder
34 : public ConstStmtVisitor<CastedAllocFinder, TypeCallPair> {
35 IdentifierInfo *II_malloc, *II_calloc, *II_realloc;
36
37 public:
38 struct CallRecord {
39 ExprParent CastedExprParent;
40 const Expr *CastedExpr;
41 const TypeSourceInfo *ExplicitCastType;
42 const CallExpr *AllocCall;
43
CallRecord__anon3b837e310111::CastedAllocFinder::CallRecord44 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
CastedAllocFinder(ASTContext * Ctx)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
VisitChild(ExprParent Parent,const Stmt * S)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
VisitChildren(const Stmt * S)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
VisitCastExpr(const CastExpr * E)73 TypeCallPair VisitCastExpr(const CastExpr *E) {
74 return Visit(E->getSubExpr());
75 }
76
VisitExplicitCastExpr(const ExplicitCastExpr * E)77 TypeCallPair VisitExplicitCastExpr(const ExplicitCastExpr *E) {
78 return TypeCallPair(E->getTypeInfoAsWritten(),
79 Visit(E->getSubExpr()).second);
80 }
81
VisitParenExpr(const ParenExpr * E)82 TypeCallPair VisitParenExpr(const ParenExpr *E) {
83 return Visit(E->getSubExpr());
84 }
85
VisitStmt(const Stmt * S)86 TypeCallPair VisitStmt(const Stmt *S) {
87 VisitChildren(S);
88 return TypeCallPair();
89 }
90
VisitCallExpr(const CallExpr * E)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
VisitDeclStmt(const DeclStmt * S)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
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
VisitBinAdd(const BinaryOperator * E)121 void VisitBinAdd(const BinaryOperator *E) {
122 Visit(E->getLHS());
123 Visit(E->getRHS());
124 }
125
VisitImplicitCastExpr(const ImplicitCastExpr * E)126 void VisitImplicitCastExpr(const ImplicitCastExpr *E) {
127 return Visit(E->getSubExpr());
128 }
129
VisitParenExpr(const ParenExpr * E)130 void VisitParenExpr(const ParenExpr *E) {
131 return Visit(E->getSubExpr());
132 }
133
VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr * E)134 void VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E) {
135 if (E->getKind() != UETT_SizeOf)
136 return;
137
138 Sizeofs.push_back(E);
139 }
140 };
141
142 class MallocSizeofChecker : public Checker<check::ASTCodeBody> {
143 public:
checkASTCodeBody(const Decl * D,AnalysisManager & mgr,BugReporter & BR) const144 void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
145 BugReporter &BR) const {
146 AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D);
147 CastedAllocFinder Finder(&BR.getContext());
148 Finder.Visit(D->getBody());
149 for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(),
150 e = Finder.Calls.end(); i != e; ++i) {
151 QualType CastedType = i->CastedExpr->getType();
152 if (!CastedType->isPointerType())
153 continue;
154 QualType PointeeType = CastedType->getAs<PointerType>()->getPointeeType();
155 if (PointeeType->isVoidType())
156 continue;
157
158 for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(),
159 ae = i->AllocCall->arg_end(); ai != ae; ++ai) {
160 if (!(*ai)->getType()->isIntegerType())
161 continue;
162
163 SizeofFinder SFinder;
164 SFinder.Visit(*ai);
165 if (SFinder.Sizeofs.size() != 1)
166 continue;
167
168 QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument();
169 if (!BR.getContext().hasSameUnqualifiedType(PointeeType, SizeofType)) {
170 const TypeSourceInfo *TSI = 0;
171 if (i->CastedExprParent.is<const VarDecl *>()) {
172 TSI =
173 i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo();
174 } else {
175 TSI = i->ExplicitCastType;
176 }
177
178 SmallString<64> buf;
179 llvm::raw_svector_ostream OS(buf);
180
181 OS << "Result of '"
182 << i->AllocCall->getDirectCallee()->getIdentifier()->getName()
183 << "' is converted to type '"
184 << CastedType.getAsString() << "', whose pointee type '"
185 << PointeeType.getAsString() << "' is incompatible with "
186 << "sizeof operand type '" << SizeofType.getAsString() << "'";
187 llvm::SmallVector<SourceRange, 4> Ranges;
188 Ranges.push_back(i->AllocCall->getCallee()->getSourceRange());
189 Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange());
190 if (TSI)
191 Ranges.push_back(TSI->getTypeLoc().getSourceRange());
192
193 PathDiagnosticLocation L =
194 PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(),
195 BR.getSourceManager(), ADC);
196
197 BR.EmitBasicReport(D, "allocator sizeof operand mismatch",
198 categories::UnixAPI,
199 OS.str(),
200 L, Ranges.data(), Ranges.size());
201 }
202 }
203 }
204 }
205 };
206
207 }
208
registerMallocSizeofChecker(CheckerManager & mgr)209 void ento::registerMallocSizeofChecker(CheckerManager &mgr) {
210 mgr.registerChecker<MallocSizeofChecker>();
211 }
212