xref: /freebsd/contrib/llvm-project/clang/lib/StaticAnalyzer/Checkers/MallocSizeofChecker.cpp (revision ebacd8013fe5f7fdf9f6a5b286f6680dd2891036) 
1 // MallocSizeofChecker.cpp - Check for dubious malloc arguments ---*- C++ -*-=//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // Reports inconsistencies between the casted type of the return value of a
10 // malloc/calloc/realloc call and the operand of any sizeof expressions
11 // contained within its argument(s).
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
16 #include "clang/AST/StmtVisitor.h"
17 #include "clang/AST/TypeLoc.h"
18 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
19 #include "clang/StaticAnalyzer/Core/Checker.h"
20 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
21 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
22 #include "llvm/ADT/SmallString.h"
23 #include "llvm/Support/raw_ostream.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 
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 (const Stmt *Child : S->children())
68       if (Child)
69         VisitChild(S, Child);
70   }
71 
72   TypeCallPair VisitCastExpr(const CastExpr *E) {
73     return Visit(E->getSubExpr());
74   }
75 
76   TypeCallPair VisitExplicitCastExpr(const ExplicitCastExpr *E) {
77     return TypeCallPair(E->getTypeInfoAsWritten(),
78                         Visit(E->getSubExpr()).second);
79   }
80 
81   TypeCallPair VisitParenExpr(const ParenExpr *E) {
82     return Visit(E->getSubExpr());
83   }
84 
85   TypeCallPair VisitStmt(const Stmt *S) {
86     VisitChildren(S);
87     return TypeCallPair();
88   }
89 
90   TypeCallPair VisitCallExpr(const CallExpr *E) {
91     VisitChildren(E);
92     const FunctionDecl *FD = E->getDirectCallee();
93     if (FD) {
94       IdentifierInfo *II = FD->getIdentifier();
95       if (II == II_malloc || II == II_calloc || II == II_realloc)
96         return TypeCallPair((const TypeSourceInfo *)nullptr, E);
97     }
98     return TypeCallPair();
99   }
100 
101   TypeCallPair VisitDeclStmt(const DeclStmt *S) {
102     for (const auto *I : S->decls())
103       if (const VarDecl *VD = dyn_cast<VarDecl>(I))
104         if (const Expr *Init = VD->getInit())
105           VisitChild(VD, Init);
106     return TypeCallPair();
107   }
108 };
109 
110 class SizeofFinder : public ConstStmtVisitor<SizeofFinder> {
111 public:
112   std::vector<const UnaryExprOrTypeTraitExpr *> Sizeofs;
113 
114   void VisitBinMul(const BinaryOperator *E) {
115     Visit(E->getLHS());
116     Visit(E->getRHS());
117   }
118 
119   void VisitImplicitCastExpr(const ImplicitCastExpr *E) {
120     return Visit(E->getSubExpr());
121   }
122 
123   void VisitParenExpr(const ParenExpr *E) {
124     return Visit(E->getSubExpr());
125   }
126 
127   void VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E) {
128     if (E->getKind() != UETT_SizeOf)
129       return;
130 
131     Sizeofs.push_back(E);
132   }
133 };
134 
135 // Determine if the pointee and sizeof types are compatible.  Here
136 // we ignore constness of pointer types.
137 static bool typesCompatible(ASTContext &C, QualType A, QualType B) {
138   // sizeof(void*) is compatible with any other pointer.
139   if (B->isVoidPointerType() && A->getAs<PointerType>())
140     return true;
141 
142   // sizeof(pointer type) is compatible with void*
143   if (A->isVoidPointerType() && B->getAs<PointerType>())
144     return true;
145 
146   while (true) {
147     A = A.getCanonicalType();
148     B = B.getCanonicalType();
149 
150     if (A.getTypePtr() == B.getTypePtr())
151       return true;
152 
153     if (const PointerType *ptrA = A->getAs<PointerType>())
154       if (const PointerType *ptrB = B->getAs<PointerType>()) {
155         A = ptrA->getPointeeType();
156         B = ptrB->getPointeeType();
157         continue;
158       }
159 
160     break;
161   }
162 
163   return false;
164 }
165 
166 static bool compatibleWithArrayType(ASTContext &C, QualType PT, QualType T) {
167   // Ex: 'int a[10][2]' is compatible with 'int', 'int[2]', 'int[10][2]'.
168   while (const ArrayType *AT = T->getAsArrayTypeUnsafe()) {
169     QualType ElemType = AT->getElementType();
170     if (typesCompatible(C, PT, AT->getElementType()))
171       return true;
172     T = ElemType;
173   }
174 
175   return false;
176 }
177 
178 class MallocSizeofChecker : public Checker<check::ASTCodeBody> {
179 public:
180   void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
181                         BugReporter &BR) const {
182     AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D);
183     CastedAllocFinder Finder(&BR.getContext());
184     Finder.Visit(D->getBody());
185     for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(),
186          e = Finder.Calls.end(); i != e; ++i) {
187       QualType CastedType = i->CastedExpr->getType();
188       if (!CastedType->isPointerType())
189         continue;
190       QualType PointeeType = CastedType->getPointeeType();
191       if (PointeeType->isVoidType())
192         continue;
193 
194       for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(),
195            ae = i->AllocCall->arg_end(); ai != ae; ++ai) {
196         if (!(*ai)->getType()->isIntegralOrUnscopedEnumerationType())
197           continue;
198 
199         SizeofFinder SFinder;
200         SFinder.Visit(*ai);
201         if (SFinder.Sizeofs.size() != 1)
202           continue;
203 
204         QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument();
205 
206         if (typesCompatible(BR.getContext(), PointeeType, SizeofType))
207           continue;
208 
209         // If the argument to sizeof is an array, the result could be a
210         // pointer to any array element.
211         if (compatibleWithArrayType(BR.getContext(), PointeeType, SizeofType))
212           continue;
213 
214         const TypeSourceInfo *TSI = nullptr;
215         if (i->CastedExprParent.is<const VarDecl *>()) {
216           TSI =
217               i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo();
218         } else {
219           TSI = i->ExplicitCastType;
220         }
221 
222         SmallString<64> buf;
223         llvm::raw_svector_ostream OS(buf);
224 
225         OS << "Result of ";
226         const FunctionDecl *Callee = i->AllocCall->getDirectCallee();
227         if (Callee && Callee->getIdentifier())
228           OS << '\'' << Callee->getIdentifier()->getName() << '\'';
229         else
230           OS << "call";
231         OS << " is converted to a pointer of type '" << PointeeType
232            << "', which is incompatible with "
233            << "sizeof operand type '" << SizeofType << "'";
234         SmallVector<SourceRange, 4> Ranges;
235         Ranges.push_back(i->AllocCall->getCallee()->getSourceRange());
236         Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange());
237         if (TSI)
238           Ranges.push_back(TSI->getTypeLoc().getSourceRange());
239 
240         PathDiagnosticLocation L =
241             PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(),
242                 BR.getSourceManager(), ADC);
243 
244         BR.EmitBasicReport(D, this, "Allocator sizeof operand mismatch",
245                            categories::UnixAPI, OS.str(), L, Ranges);
246       }
247     }
248   }
249 };
250 
251 }
252 
253 void ento::registerMallocSizeofChecker(CheckerManager &mgr) {
254   mgr.registerChecker<MallocSizeofChecker>();
255 }
256 
257 bool ento::shouldRegisterMallocSizeofChecker(const CheckerManager &mgr) {
258   return true;
259 }
260