clang 19.0.0git
CastToStructChecker.cpp
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1//=== CastToStructChecker.cpp ----------------------------------*- 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// This files defines CastToStructChecker, a builtin checker that checks for
10// cast from non-struct pointer to struct pointer and widening struct data cast.
11// This check corresponds to CWE-588.
12//
13//===----------------------------------------------------------------------===//
14
21
22using namespace clang;
23using namespace ento;
24
25namespace {
26class CastToStructVisitor : public RecursiveASTVisitor<CastToStructVisitor> {
27 BugReporter &BR;
28 const CheckerBase *Checker;
30
31public:
32 explicit CastToStructVisitor(BugReporter &B, const CheckerBase *Checker,
34 : BR(B), Checker(Checker), AC(A) {}
35 bool VisitCastExpr(const CastExpr *CE);
36};
37}
38
39bool CastToStructVisitor::VisitCastExpr(const CastExpr *CE) {
40 const Expr *E = CE->getSubExpr();
41 ASTContext &Ctx = AC->getASTContext();
42 QualType OrigTy = Ctx.getCanonicalType(E->getType());
43 QualType ToTy = Ctx.getCanonicalType(CE->getType());
44
45 const PointerType *OrigPTy = dyn_cast<PointerType>(OrigTy.getTypePtr());
46 const PointerType *ToPTy = dyn_cast<PointerType>(ToTy.getTypePtr());
47
48 if (!ToPTy || !OrigPTy)
49 return true;
50
51 QualType OrigPointeeTy = OrigPTy->getPointeeType();
52 QualType ToPointeeTy = ToPTy->getPointeeType();
53
54 if (!ToPointeeTy->isStructureOrClassType())
55 return true;
56
57 // We allow cast from void*.
58 if (OrigPointeeTy->isVoidType())
59 return true;
60
61 // Now the cast-to-type is struct pointer, the original type is not void*.
62 if (!OrigPointeeTy->isRecordType()) {
63 SourceRange Sr[1] = {CE->getSourceRange()};
64 PathDiagnosticLocation Loc(CE, BR.getSourceManager(), AC);
65 BR.EmitBasicReport(
66 AC->getDecl(), Checker, "Cast from non-struct type to struct type",
67 categories::LogicError, "Casting a non-structure type to a structure "
68 "type and accessing a field can lead to memory "
69 "access errors or data corruption.",
70 Loc, Sr);
71 } else {
72 // Don't warn when size of data is unknown.
73 const auto *U = dyn_cast<UnaryOperator>(E);
74 if (!U || U->getOpcode() != UO_AddrOf)
75 return true;
76
77 // Don't warn for references
78 const ValueDecl *VD = nullptr;
79 if (const auto *SE = dyn_cast<DeclRefExpr>(U->getSubExpr()))
80 VD = SE->getDecl();
81 else if (const auto *SE = dyn_cast<MemberExpr>(U->getSubExpr()))
82 VD = SE->getMemberDecl();
83 if (!VD || VD->getType()->isReferenceType())
84 return true;
85
86 if (ToPointeeTy->isIncompleteType() ||
87 OrigPointeeTy->isIncompleteType())
88 return true;
89
90 // Warn when there is widening cast.
91 unsigned ToWidth = Ctx.getTypeInfo(ToPointeeTy).Width;
92 unsigned OrigWidth = Ctx.getTypeInfo(OrigPointeeTy).Width;
93 if (ToWidth <= OrigWidth)
94 return true;
95
96 PathDiagnosticLocation Loc(CE, BR.getSourceManager(), AC);
97 BR.EmitBasicReport(AC->getDecl(), Checker, "Widening cast to struct type",
99 "Casting data to a larger structure type and accessing "
100 "a field can lead to memory access errors or data "
101 "corruption.",
102 Loc, CE->getSourceRange());
103 }
104
105 return true;
106}
107
108namespace {
109class CastToStructChecker : public Checker<check::ASTCodeBody> {
110public:
111 void checkASTCodeBody(const Decl *D, AnalysisManager &Mgr,
112 BugReporter &BR) const {
113 CastToStructVisitor Visitor(BR, this, Mgr.getAnalysisDeclContext(D));
114 Visitor.TraverseDecl(const_cast<Decl *>(D));
115 }
116};
117} // end anonymous namespace
118
119void ento::registerCastToStructChecker(CheckerManager &mgr) {
120 mgr.registerChecker<CastToStructChecker>();
121}
122
123bool ento::shouldRegisterCastToStructChecker(const CheckerManager &mgr) {
124 return true;
125}
const Decl * D
Expr * E
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:186
CanQualType getCanonicalType(QualType T) const
Return the canonical (structural) type corresponding to the specified potentially non-canonical type ...
Definition: ASTContext.h:2616
TypeInfo getTypeInfo(const Type *T) const
Get the size and alignment of the specified complete type in bits.
AnalysisDeclContext contains the context data for the function, method or block under analysis.
CastExpr - Base class for type casts, including both implicit casts (ImplicitCastExpr) and explicit c...
Definition: Expr.h:3488
Expr * getSubExpr()
Definition: Expr.h:3538
Decl - This represents one declaration (or definition), e.g.
Definition: DeclBase.h:86
This represents one expression.
Definition: Expr.h:110
QualType getType() const
Definition: Expr.h:142
PointerType - C99 6.7.5.1 - Pointer Declarators.
Definition: Type.h:3158
QualType getPointeeType() const
Definition: Type.h:3168
A (possibly-)qualified type.
Definition: Type.h:942
const Type * getTypePtr() const
Retrieves a pointer to the underlying (unqualified) type.
Definition: Type.h:7744
A class that does preorder or postorder depth-first traversal on the entire Clang AST and visits each...
A trivial tuple used to represent a source range.
SourceRange getSourceRange() const LLVM_READONLY
SourceLocation tokens are not useful in isolation - they are low level value objects created/interpre...
Definition: Stmt.cpp:326
bool isVoidType() const
Definition: Type.h:8296
bool isReferenceType() const
Definition: Type.h:8011
bool isIncompleteType(NamedDecl **Def=nullptr) const
Types are partitioned into 3 broad categories (C99 6.2.5p1): object types, function types,...
Definition: Type.cpp:2361
bool isStructureOrClassType() const
Definition: Type.cpp:657
bool isRecordType() const
Definition: Type.h:8093
Represent the declaration of a variable (in which case it is an lvalue) a function (in which case it ...
Definition: Decl.h:706
QualType getType() const
Definition: Decl.h:717
AnalysisDeclContext * getAnalysisDeclContext(const Decl *D)
BugReporter is a utility class for generating PathDiagnostics for analysis.
Definition: BugReporter.h:585
CHECKER * registerChecker(AT &&... Args)
Used to register checkers.
The JSON file list parser is used to communicate input to InstallAPI.
uint64_t Width
Definition: ASTContext.h:157