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/DynamicExtent.h" 20 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 21 22 using namespace clang; 23 using namespace ento; 24 25 namespace { 26 class ArrayBoundChecker : 27 public Checker<check::Location> { 28 mutable std::unique_ptr<BuiltinBug> BT; 29 30 public: 31 void checkLocation(SVal l, bool isLoad, const Stmt* S, 32 CheckerContext &C) const; 33 }; 34 } 35 36 void ArrayBoundChecker::checkLocation(SVal l, bool isLoad, const Stmt* LoadS, 37 CheckerContext &C) const { 38 // Check for out of bound array element access. 39 const MemRegion *R = l.getAsRegion(); 40 if (!R) 41 return; 42 43 const ElementRegion *ER = dyn_cast<ElementRegion>(R); 44 if (!ER) 45 return; 46 47 // Get the index of the accessed element. 48 DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>(); 49 50 // Zero index is always in bound, this also passes ElementRegions created for 51 // pointer casts. 52 if (Idx.isZeroConstant()) 53 return; 54 55 ProgramStateRef state = C.getState(); 56 57 // Get the size of the array. 58 DefinedOrUnknownSVal ElementCount = getDynamicElementCount( 59 state, ER->getSuperRegion(), C.getSValBuilder(), ER->getValueType()); 60 61 ProgramStateRef StInBound, StOutBound; 62 std::tie(StInBound, StOutBound) = state->assumeInBoundDual(Idx, ElementCount); 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 = 79 std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N); 80 81 report->addRange(LoadS->getSourceRange()); 82 C.emitReport(std::move(report)); 83 return; 84 } 85 86 // Array bound check succeeded. From this point forward the array bound 87 // should always succeed. 88 C.addTransition(StInBound); 89 } 90 91 void ento::registerArrayBoundChecker(CheckerManager &mgr) { 92 mgr.registerChecker<ArrayBoundChecker>(); 93 } 94 95 bool ento::shouldRegisterArrayBoundChecker(const CheckerManager &mgr) { 96 return true; 97 } 98