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 AnalysisDeclContext* AC; 28 29 public: 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 37 void 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 44 void 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 79 namespace { 80 class SizeofPointerChecker : public Checker<check::ASTCodeBody> { 81 public: 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 90 void ento::registerSizeofPointerChecker(CheckerManager &mgr) { 91 mgr.registerChecker<SizeofPointerChecker>(); 92 } 93
