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