1//==- CheckSizeofPointer.cpp - Check for sizeof on pointers ------*- C++ -*-==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10//  This file defines a check for unintended use of sizeof() on pointer
11//  expressions.
12//
13//===----------------------------------------------------------------------===//
14
15#include "ClangSACheckers.h"
16#include "clang/AST/StmtVisitor.h"
17#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
18#include "clang/StaticAnalyzer/Core/Checker.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
20
21using namespace clang;
22using namespace ento;
23
24namespace {
25class WalkAST : public StmtVisitor<WalkAST> {
26  BugReporter &BR;
27  AnalysisDeclContext* AC;
28
29public:
30  WalkAST(BugReporter &br, AnalysisDeclContext* ac) : BR(br), AC(ac) {}
31  void VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E);
32  void VisitStmt(Stmt *S) { VisitChildren(S); }
33  void VisitChildren(Stmt *S);
34};
35}
36
37void WalkAST::VisitChildren(Stmt *S) {
38  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
39    if (Stmt *child = *I)
40      Visit(child);
41}
42
43// CWE-467: Use of sizeof() on a Pointer Type
44void WalkAST::VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E) {
45  if (E->getKind() != UETT_SizeOf)
46    return;
47
48  // If an explicit type is used in the code, usually the coder knows what he is
49  // doing.
50  if (E->isArgumentType())
51    return;
52
53  QualType T = E->getTypeOfArgument();
54  if (T->isPointerType()) {
55
56    // Many false positives have the form 'sizeof *p'. This is reasonable
57    // because people know what they are doing when they intentionally
58    // dereference the pointer.
59    Expr *ArgEx = E->getArgumentExpr();
60    if (!isa<DeclRefExpr>(ArgEx->IgnoreParens()))
61      return;
62
63    PathDiagnosticLocation ELoc =
64      PathDiagnosticLocation::createBegin(E, BR.getSourceManager(), AC);
65    BR.EmitBasicReport(AC->getDecl(),
66                       "Potential unintended use of sizeof() on pointer type",
67                       categories::LogicError,
68                       "The code calls sizeof() on a pointer type. "
69                       "This can produce an unexpected result.",
70                       ELoc, ArgEx->getSourceRange());
71  }
72}
73
74//===----------------------------------------------------------------------===//
75// SizeofPointerChecker
76//===----------------------------------------------------------------------===//
77
78namespace {
79class SizeofPointerChecker : public Checker<check::ASTCodeBody> {
80public:
81  void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
82                        BugReporter &BR) const {
83    WalkAST walker(BR, mgr.getAnalysisDeclContext(D));
84    walker.Visit(D->getBody());
85  }
86};
87}
88
89void ento::registerSizeofPointerChecker(CheckerManager &mgr) {
90  mgr.registerChecker<SizeofPointerChecker>();
91}
92