xref: /openbsd-src/gnu/llvm/clang/lib/StaticAnalyzer/Checkers/PointerSubChecker.cpp (revision ec727ea710c91afd8ce4f788c5aaa8482b7b69b2)
1e5dd7070Spatrick //=== PointerSubChecker.cpp - Pointer subtraction checker ------*- C++ -*--===//
2e5dd7070Spatrick //
3e5dd7070Spatrick // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4e5dd7070Spatrick // See https://llvm.org/LICENSE.txt for license information.
5e5dd7070Spatrick // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6e5dd7070Spatrick //
7e5dd7070Spatrick //===----------------------------------------------------------------------===//
8e5dd7070Spatrick //
9e5dd7070Spatrick // This files defines PointerSubChecker, a builtin checker that checks for
10e5dd7070Spatrick // pointer subtractions on two pointers pointing to different memory chunks.
11e5dd7070Spatrick // This check corresponds to CWE-469.
12e5dd7070Spatrick //
13e5dd7070Spatrick //===----------------------------------------------------------------------===//
14e5dd7070Spatrick 
15e5dd7070Spatrick #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
16e5dd7070Spatrick #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
17e5dd7070Spatrick #include "clang/StaticAnalyzer/Core/Checker.h"
18e5dd7070Spatrick #include "clang/StaticAnalyzer/Core/CheckerManager.h"
19e5dd7070Spatrick #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20e5dd7070Spatrick 
21e5dd7070Spatrick using namespace clang;
22e5dd7070Spatrick using namespace ento;
23e5dd7070Spatrick 
24e5dd7070Spatrick namespace {
25e5dd7070Spatrick class PointerSubChecker
26e5dd7070Spatrick   : public Checker< check::PreStmt<BinaryOperator> > {
27e5dd7070Spatrick   mutable std::unique_ptr<BuiltinBug> BT;
28e5dd7070Spatrick 
29e5dd7070Spatrick public:
30e5dd7070Spatrick   void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
31e5dd7070Spatrick };
32e5dd7070Spatrick }
33e5dd7070Spatrick 
checkPreStmt(const BinaryOperator * B,CheckerContext & C) const34e5dd7070Spatrick void PointerSubChecker::checkPreStmt(const BinaryOperator *B,
35e5dd7070Spatrick                                      CheckerContext &C) const {
36e5dd7070Spatrick   // When doing pointer subtraction, if the two pointers do not point to the
37e5dd7070Spatrick   // same memory chunk, emit a warning.
38e5dd7070Spatrick   if (B->getOpcode() != BO_Sub)
39e5dd7070Spatrick     return;
40e5dd7070Spatrick 
41e5dd7070Spatrick   SVal LV = C.getSVal(B->getLHS());
42e5dd7070Spatrick   SVal RV = C.getSVal(B->getRHS());
43e5dd7070Spatrick 
44e5dd7070Spatrick   const MemRegion *LR = LV.getAsRegion();
45e5dd7070Spatrick   const MemRegion *RR = RV.getAsRegion();
46e5dd7070Spatrick 
47e5dd7070Spatrick   if (!(LR && RR))
48e5dd7070Spatrick     return;
49e5dd7070Spatrick 
50e5dd7070Spatrick   const MemRegion *BaseLR = LR->getBaseRegion();
51e5dd7070Spatrick   const MemRegion *BaseRR = RR->getBaseRegion();
52e5dd7070Spatrick 
53e5dd7070Spatrick   if (BaseLR == BaseRR)
54e5dd7070Spatrick     return;
55e5dd7070Spatrick 
56e5dd7070Spatrick   // Allow arithmetic on different symbolic regions.
57e5dd7070Spatrick   if (isa<SymbolicRegion>(BaseLR) || isa<SymbolicRegion>(BaseRR))
58e5dd7070Spatrick     return;
59e5dd7070Spatrick 
60e5dd7070Spatrick   if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
61e5dd7070Spatrick     if (!BT)
62e5dd7070Spatrick       BT.reset(
63e5dd7070Spatrick           new BuiltinBug(this, "Pointer subtraction",
64e5dd7070Spatrick                          "Subtraction of two pointers that do not point to "
65e5dd7070Spatrick                          "the same memory chunk may cause incorrect result."));
66e5dd7070Spatrick     auto R =
67e5dd7070Spatrick         std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N);
68e5dd7070Spatrick     R->addRange(B->getSourceRange());
69e5dd7070Spatrick     C.emitReport(std::move(R));
70e5dd7070Spatrick   }
71e5dd7070Spatrick }
72e5dd7070Spatrick 
registerPointerSubChecker(CheckerManager & mgr)73e5dd7070Spatrick void ento::registerPointerSubChecker(CheckerManager &mgr) {
74e5dd7070Spatrick   mgr.registerChecker<PointerSubChecker>();
75e5dd7070Spatrick }
76e5dd7070Spatrick 
shouldRegisterPointerSubChecker(const CheckerManager & mgr)77*ec727ea7Spatrick bool ento::shouldRegisterPointerSubChecker(const CheckerManager &mgr) {
78e5dd7070Spatrick   return true;
79e5dd7070Spatrick }
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