1 //== ArrayBoundChecker.cpp ------------------------------*- C++ -*--==// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file defines ArrayBoundChecker, which is a path-sensitive check 10 // which looks for an out-of-bound array element access. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" 15 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 16 #include "clang/StaticAnalyzer/Core/Checker.h" 17 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 19 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 20 21 using namespace clang; 22 using namespace ento; 23 24 namespace { 25 class ArrayBoundChecker : 26 public Checker<check::Location> { 27 mutable std::unique_ptr<BuiltinBug> BT; 28 29 public: 30 void checkLocation(SVal l, bool isLoad, const Stmt* S, 31 CheckerContext &C) const; 32 }; 33 } 34 35 void ArrayBoundChecker::checkLocation(SVal l, bool isLoad, const Stmt* LoadS, 36 CheckerContext &C) const { 37 // Check for out of bound array element access. 38 const MemRegion *R = l.getAsRegion(); 39 if (!R) 40 return; 41 42 const ElementRegion *ER = dyn_cast<ElementRegion>(R); 43 if (!ER) 44 return; 45 46 // Get the index of the accessed element. 47 DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>(); 48 49 // Zero index is always in bound, this also passes ElementRegions created for 50 // pointer casts. 51 if (Idx.isZeroConstant()) 52 return; 53 54 ProgramStateRef state = C.getState(); 55 56 // Get the size of the array. 57 DefinedOrUnknownSVal NumElements 58 = C.getStoreManager().getSizeInElements(state, ER->getSuperRegion(), 59 ER->getValueType()); 60 61 ProgramStateRef StInBound = state->assumeInBound(Idx, NumElements, true); 62 ProgramStateRef StOutBound = state->assumeInBound(Idx, NumElements, false); 63 if (StOutBound && !StInBound) { 64 ExplodedNode *N = C.generateErrorNode(StOutBound); 65 if (!N) 66 return; 67 68 if (!BT) 69 BT.reset(new BuiltinBug( 70 this, "Out-of-bound array access", 71 "Access out-of-bound array element (buffer overflow)")); 72 73 // FIXME: It would be nice to eventually make this diagnostic more clear, 74 // e.g., by referencing the original declaration or by saying *why* this 75 // reference is outside the range. 76 77 // Generate a report for this bug. 78 auto report = llvm::make_unique<BugReport>(*BT, BT->getDescription(), N); 79 80 report->addRange(LoadS->getSourceRange()); 81 C.emitReport(std::move(report)); 82 return; 83 } 84 85 // Array bound check succeeded. From this point forward the array bound 86 // should always succeed. 87 C.addTransition(StInBound); 88 } 89 90 void ento::registerArrayBoundChecker(CheckerManager &mgr) { 91 mgr.registerChecker<ArrayBoundChecker>(); 92 } 93 94 bool ento::shouldRegisterArrayBoundChecker(const LangOptions &LO) { 95 return true; 96 } 97