| 1 | //=== PointerSubChecker.cpp - Pointer subtraction checker ------*- 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 files defines PointerSubChecker, a builtin checker that checks for |
| 10 | // pointer subtractions on two pointers pointing to different memory chunks. |
| 11 | // This check corresponds to CWE-469. |
| 12 | // |
| 13 | //===----------------------------------------------------------------------===// |
| 14 | |
| 15 | #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" |
| 16 | #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" |
| 17 | #include "clang/StaticAnalyzer/Core/Checker.h" |
| 18 | #include "clang/StaticAnalyzer/Core/CheckerManager.h" |
| 19 | #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" |
| 20 | #include "llvm/ADT/StringRef.h" |
| 21 | |
| 22 | using namespace clang; |
| 23 | using namespace ento; |
| 24 | |
| 25 | namespace { |
| 26 | class PointerSubChecker |
| 27 | : public Checker< check::PreStmt<BinaryOperator> > { |
| 28 | const BugType BT{this, "Pointer subtraction"}; |
| 29 | |
| 30 | public: |
| 31 | void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const; |
| 32 | }; |
| 33 | } |
| 34 | |
| 35 | void PointerSubChecker::checkPreStmt(const BinaryOperator *B, |
| 36 | CheckerContext &C) const { |
| 37 | // When doing pointer subtraction, if the two pointers do not point to the |
| 38 | // same memory chunk, emit a warning. |
| 39 | if (B->getOpcode() != BO_Sub) |
| 40 | return; |
| 41 | |
| 42 | SVal LV = C.getSVal(B->getLHS()); |
| 43 | SVal RV = C.getSVal(B->getRHS()); |
| 44 | |
| 45 | const MemRegion *LR = LV.getAsRegion(); |
| 46 | const MemRegion *RR = RV.getAsRegion(); |
| 47 | |
| 48 | if (!(LR && RR)) |
| 49 | return; |
| 50 | |
| 51 | const MemRegion *BaseLR = LR->getBaseRegion(); |
| 52 | const MemRegion *BaseRR = RR->getBaseRegion(); |
| 53 | |
| 54 | if (BaseLR == BaseRR) |
| 55 | return; |
| 56 | |
| 57 | // Allow arithmetic on different symbolic regions. |
| 58 | if (isa<SymbolicRegion>(Val: BaseLR) || isa<SymbolicRegion>(Val: BaseRR)) |
| 59 | return; |
| 60 | |
| 61 | if (ExplodedNode *N = C.generateNonFatalErrorNode()) { |
| 62 | constexpr llvm::StringLiteral Msg = |
| 63 | "Subtraction of two pointers that do not point to the same memory " |
| 64 | "chunk may cause incorrect result."; |
| 65 | auto R = std::make_unique<PathSensitiveBugReport>(args: BT, args: Msg, args&: N); |
| 66 | R->addRange(R: B->getSourceRange()); |
| 67 | C.emitReport(R: std::move(R)); |
| 68 | } |
| 69 | } |
| 70 | |
| 71 | void ento::registerPointerSubChecker(CheckerManager &mgr) { |
| 72 | mgr.registerChecker<PointerSubChecker>(); |
| 73 | } |
| 74 | |
| 75 | bool ento::shouldRegisterPointerSubChecker(const CheckerManager &mgr) { |
| 76 | return true; |
| 77 | } |
| 78 |