CheckSizeofPointer.cpp revision 10a61586e12fcd94dad877cbcf09cc34aec980d8 
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    SourceRange R = ArgEx->getSourceRange();
64    PathDiagnosticLocation ELoc =
65      PathDiagnosticLocation::createBegin(E, BR.getSourceManager(), AC);
66    BR.EmitBasicReport(AC->getDecl(),
67                       "Potential unintended use of sizeof() on pointer type",
68                       "Logic",
69                       "The code calls sizeof() on a pointer type. "
70                       "This can produce an unexpected result.",
71                       ELoc, &R, 1);
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, mgr.getAnalysisDeclContext(D));
85    walker.Visit(D->getBody());
86  }
87};
88}
89
90void ento::registerSizeofPointerChecker(CheckerManager &mgr) {
91  mgr.registerChecker<SizeofPointerChecker>();
92}
93