Clang Project

clang_source_code/lib/StaticAnalyzer/Checkers/CheckSizeofPointer.cpp
1//==- CheckSizeofPointer.cpp - Check for sizeof on pointers ------*- 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 file defines a check for unintended use of sizeof() on pointer
10//  expressions.
11//
12//===----------------------------------------------------------------------===//
13
14#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
15#include "clang/AST/StmtVisitor.h"
16#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
17#include "clang/StaticAnalyzer/Core/Checker.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
19
20using namespace clang;
21using namespace ento;
22
23namespace {
24class WalkAST : public StmtVisitor<WalkAST> {
25  BugReporter &BR;
26  const CheckerBase *Checker;
27  AnalysisDeclContext* AC;
28
29public:
30  WalkAST(BugReporter &br, const CheckerBase *checker, AnalysisDeclContext *ac)
31      : BR(br), Checker(checker), AC(ac) {}
32  void VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E);
33  void VisitStmt(Stmt *S) { VisitChildren(S); }
34  void VisitChildren(Stmt *S);
35};
36}
37
38void WalkAST::VisitChildren(Stmt *S) {
39  for (Stmt *Child : S->children())
40    if (Child)
41      Visit(Child);
42}
43
44// CWE-467: Use of sizeof() on a Pointer Type
45void WalkAST::VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E) {
46  if (E->getKind() != UETT_SizeOf)
47    return;
48
49  // If an explicit type is used in the code, usually the coder knows what they are
50  // doing.
51  if (E->isArgumentType())
52    return;
53
54  QualType T = E->getTypeOfArgument();
55  if (T->isPointerType()) {
56
57    // Many false positives have the form 'sizeof *p'. This is reasonable
58    // because people know what they are doing when they intentionally
59    // dereference the pointer.
60    Expr *ArgEx = E->getArgumentExpr();
61    if (!isa<DeclRefExpr>(ArgEx->IgnoreParens()))
62      return;
63
64    PathDiagnosticLocation ELoc =
65      PathDiagnosticLocation::createBegin(E, BR.getSourceManager(), AC);
66    BR.EmitBasicReport(AC->getDecl(), Checker,
67                       "Potential unintended use of sizeof() on pointer type",
68                       categories::LogicError,
69                       "The code calls sizeof() on a pointer type. "
70                       "This can produce an unexpected result.",
71                       ELoc, ArgEx->getSourceRange());
72  }
73}
74
75//===----------------------------------------------------------------------===//
76// SizeofPointerChecker
77//===----------------------------------------------------------------------===//
78
79namespace {
80class SizeofPointerChecker : public Checker<check::ASTCodeBody> {
81public:
82  void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
83                        BugReporter &BR) const {
84    WalkAST walker(BR, this, mgr.getAnalysisDeclContext(D));
85    walker.Visit(D->getBody());
86  }
87};
88}
89
90void ento::registerSizeofPointerChecker(CheckerManager &mgr) {
91  mgr.registerChecker<SizeofPointerChecker>();
92}
93
94bool ento::shouldRegisterSizeofPointerChecker(const LangOptions &LO) {
95  return true;
96}
97
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