1 // MallocSizeofChecker.cpp - Check for dubious malloc arguments ---*- C++ -*-=//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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).
14 //===----------------------------------------------------------------------===//
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"
26 using namespace clang;
31 typedef std::pair<const TypeSourceInfo *, const CallExpr *> TypeCallPair;
32 typedef llvm::PointerUnion<const Stmt *, const VarDecl *> ExprParent;
34 class CastedAllocFinder
35 : public ConstStmtVisitor<CastedAllocFinder, TypeCallPair> {
36 IdentifierInfo *II_malloc, *II_calloc, *II_realloc;
40 ExprParent CastedExprParent;
41 const Expr *CastedExpr;
42 const TypeSourceInfo *ExplicitCastType;
43 const CallExpr *AllocCall;
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) {}
52 typedef std::vector<CallRecord> CallVec;
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")) {}
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,
67 void VisitChildren(const Stmt *S) {
68 for (const Stmt *Child : S->children())
73 TypeCallPair VisitCastExpr(const CastExpr *E) {
74 return Visit(E->getSubExpr());
77 TypeCallPair VisitExplicitCastExpr(const ExplicitCastExpr *E) {
78 return TypeCallPair(E->getTypeInfoAsWritten(),
79 Visit(E->getSubExpr()).second);
82 TypeCallPair VisitParenExpr(const ParenExpr *E) {
83 return Visit(E->getSubExpr());
86 TypeCallPair VisitStmt(const Stmt *S) {
88 return TypeCallPair();
91 TypeCallPair VisitCallExpr(const CallExpr *E) {
93 const FunctionDecl *FD = E->getDirectCallee();
95 IdentifierInfo *II = FD->getIdentifier();
96 if (II == II_malloc || II == II_calloc || II == II_realloc)
97 return TypeCallPair((const TypeSourceInfo *)nullptr, E);
99 return TypeCallPair();
102 TypeCallPair VisitDeclStmt(const DeclStmt *S) {
103 for (const auto *I : S->decls())
104 if (const VarDecl *VD = dyn_cast<VarDecl>(I))
105 if (const Expr *Init = VD->getInit())
106 VisitChild(VD, Init);
107 return TypeCallPair();
111 class SizeofFinder : public ConstStmtVisitor<SizeofFinder> {
113 std::vector<const UnaryExprOrTypeTraitExpr *> Sizeofs;
115 void VisitBinMul(const BinaryOperator *E) {
120 void VisitImplicitCastExpr(const ImplicitCastExpr *E) {
121 return Visit(E->getSubExpr());
124 void VisitParenExpr(const ParenExpr *E) {
125 return Visit(E->getSubExpr());
128 void VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E) {
129 if (E->getKind() != UETT_SizeOf)
132 Sizeofs.push_back(E);
136 // Determine if the pointee and sizeof types are compatible. Here
137 // we ignore constness of pointer types.
138 static bool typesCompatible(ASTContext &C, QualType A, QualType B) {
139 // sizeof(void*) is compatible with any other pointer.
140 if (B->isVoidPointerType() && A->getAs<PointerType>())
144 A = A.getCanonicalType();
145 B = B.getCanonicalType();
147 if (A.getTypePtr() == B.getTypePtr())
150 if (const PointerType *ptrA = A->getAs<PointerType>())
151 if (const PointerType *ptrB = B->getAs<PointerType>()) {
152 A = ptrA->getPointeeType();
153 B = ptrB->getPointeeType();
163 static bool compatibleWithArrayType(ASTContext &C, QualType PT, QualType T) {
164 // Ex: 'int a[10][2]' is compatible with 'int', 'int[2]', 'int[10][2]'.
165 while (const ArrayType *AT = T->getAsArrayTypeUnsafe()) {
166 QualType ElemType = AT->getElementType();
167 if (typesCompatible(C, PT, AT->getElementType()))
175 class MallocSizeofChecker : public Checker<check::ASTCodeBody> {
177 void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
178 BugReporter &BR) const {
179 AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D);
180 CastedAllocFinder Finder(&BR.getContext());
181 Finder.Visit(D->getBody());
182 for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(),
183 e = Finder.Calls.end(); i != e; ++i) {
184 QualType CastedType = i->CastedExpr->getType();
185 if (!CastedType->isPointerType())
187 QualType PointeeType = CastedType->getAs<PointerType>()->getPointeeType();
188 if (PointeeType->isVoidType())
191 for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(),
192 ae = i->AllocCall->arg_end(); ai != ae; ++ai) {
193 if (!(*ai)->getType()->isIntegralOrUnscopedEnumerationType())
196 SizeofFinder SFinder;
198 if (SFinder.Sizeofs.size() != 1)
201 QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument();
203 if (typesCompatible(BR.getContext(), PointeeType, SizeofType))
206 // If the argument to sizeof is an array, the result could be a
207 // pointer to any array element.
208 if (compatibleWithArrayType(BR.getContext(), PointeeType, SizeofType))
211 const TypeSourceInfo *TSI = nullptr;
212 if (i->CastedExprParent.is<const VarDecl *>()) {
214 i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo();
216 TSI = i->ExplicitCastType;
220 llvm::raw_svector_ostream OS(buf);
223 const FunctionDecl *Callee = i->AllocCall->getDirectCallee();
224 if (Callee && Callee->getIdentifier())
225 OS << '\'' << Callee->getIdentifier()->getName() << '\'';
228 OS << " is converted to a pointer of type '"
229 << PointeeType.getAsString() << "', which is incompatible with "
230 << "sizeof operand type '" << SizeofType.getAsString() << "'";
231 SmallVector<SourceRange, 4> Ranges;
232 Ranges.push_back(i->AllocCall->getCallee()->getSourceRange());
233 Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange());
235 Ranges.push_back(TSI->getTypeLoc().getSourceRange());
237 PathDiagnosticLocation L =
238 PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(),
239 BR.getSourceManager(), ADC);
241 BR.EmitBasicReport(D, this, "Allocator sizeof operand mismatch",
242 categories::UnixAPI, OS.str(), L, Ranges);
250 void ento::registerMallocSizeofChecker(CheckerManager &mgr) {
251 mgr.registerChecker<MallocSizeofChecker>();