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
20 using namespace clang;
21 using namespace ento;
22
23 namespace {
24 class WalkAST : public StmtVisitor<WalkAST> {
25 BugReporter &BR;
26 const CheckerBase *Checker;
27 AnalysisDeclContext* AC;
28
29 public:
WalkAST(BugReporter & br,const CheckerBase * checker,AnalysisDeclContext * ac)30 WalkAST(BugReporter &br, const CheckerBase *checker, AnalysisDeclContext *ac)
31 : BR(br), Checker(checker), AC(ac) {}
32 void VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E);
VisitStmt(Stmt * S)33 void VisitStmt(Stmt *S) { VisitChildren(S); }
34 void VisitChildren(Stmt *S);
35 };
36 }
37
VisitChildren(Stmt * S)38 void 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
VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr * E)45 void 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
79 namespace {
80 class SizeofPointerChecker : public Checker<check::ASTCodeBody> {
81 public:
checkASTCodeBody(const Decl * D,AnalysisManager & mgr,BugReporter & BR) const82 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
registerSizeofPointerChecker(CheckerManager & mgr)90 void ento::registerSizeofPointerChecker(CheckerManager &mgr) {
91 mgr.registerChecker<SizeofPointerChecker>();
92 }
93
shouldRegisterSizeofPointerChecker(const LangOptions & LO)94 bool ento::shouldRegisterSizeofPointerChecker(const LangOptions &LO) {
95 return true;
96 }
97