CheckSizeofPointer.cpp revision 1d26f48dc2eea1c07431ca1519d7034a21b9bcff
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/Checker.h" 18#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.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("Potential unintended use of sizeof() on pointer type", 67 "Logic", 68 "The code calls sizeof() on a pointer type. " 69 "This can produce an unexpected result.", 70 ELoc, &R, 1); 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