| //=== PointerSubChecker.cpp - Pointer subtraction checker ------*- C++ -*--===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This files defines PointerSubChecker, a builtin checker that checks for |
| // pointer subtractions on two pointers pointing to different memory chunks. |
| // This check corresponds to CWE-469. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" |
| #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" |
| #include "clang/StaticAnalyzer/Core/Checker.h" |
| #include "clang/StaticAnalyzer/Core/CheckerManager.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" |
| |
| using namespace clang; |
| using namespace ento; |
| |
| namespace { |
| class PointerSubChecker |
| : public Checker< check::PreStmt<BinaryOperator> > { |
| mutable std::unique_ptr<BuiltinBug> BT; |
| |
| public: |
| void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const; |
| }; |
| } |
| |
| void PointerSubChecker::checkPreStmt(const BinaryOperator *B, |
| CheckerContext &C) const { |
| // When doing pointer subtraction, if the two pointers do not point to the |
| // same memory chunk, emit a warning. |
| if (B->getOpcode() != BO_Sub) |
| return; |
| |
| SVal LV = C.getSVal(B->getLHS()); |
| SVal RV = C.getSVal(B->getRHS()); |
| |
| const MemRegion *LR = LV.getAsRegion(); |
| const MemRegion *RR = RV.getAsRegion(); |
| |
| if (!(LR && RR)) |
| return; |
| |
| const MemRegion *BaseLR = LR->getBaseRegion(); |
| const MemRegion *BaseRR = RR->getBaseRegion(); |
| |
| if (BaseLR == BaseRR) |
| return; |
| |
| // Allow arithmetic on different symbolic regions. |
| if (isa<SymbolicRegion>(BaseLR) || isa<SymbolicRegion>(BaseRR)) |
| return; |
| |
| if (ExplodedNode *N = C.generateNonFatalErrorNode()) { |
| if (!BT) |
| BT.reset( |
| new BuiltinBug(this, "Pointer subtraction", |
| "Subtraction of two pointers that do not point to " |
| "the same memory chunk may cause incorrect result.")); |
| auto R = |
| std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N); |
| R->addRange(B->getSourceRange()); |
| C.emitReport(std::move(R)); |
| } |
| } |
| |
| void ento::registerPointerSubChecker(CheckerManager &mgr) { |
| mgr.registerChecker<PointerSubChecker>(); |
| } |
| |
| bool ento::shouldRegisterPointerSubChecker(const CheckerManager &mgr) { |
| return true; |
| } |