clang 10.0.0git

PointerSubChecker.cpp
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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
21 using namespace clang;
22 using namespace ento;
23
24 namespace {
25 class PointerSubChecker
26 : public Checker< check::PreStmt<BinaryOperator> > {
27 mutable std::unique_ptr<BuiltinBug> BT;
28
29 public:
30 void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
31 };
32 }
33
34 void PointerSubChecker::checkPreStmt(const BinaryOperator *B,
35 CheckerContext &C) const {
36 // When doing pointer subtraction, if the two pointers do not point to the
37 // same memory chunk, emit a warning.
38 if (B->getOpcode() != BO_Sub)
39 return;
40
41 SVal LV = C.getSVal(B->getLHS());
42 SVal RV = C.getSVal(B->getRHS());
43
44 const MemRegion *LR = LV.getAsRegion();
45 const MemRegion *RR = RV.getAsRegion();
46
47 if (!(LR && RR))
48 return;
49
50 const MemRegion *BaseLR = LR->getBaseRegion();
51 const MemRegion *BaseRR = RR->getBaseRegion();
52
53 if (BaseLR == BaseRR)
54 return;
55
56 // Allow arithmetic on different symbolic regions.
57 if (isa<SymbolicRegion>(BaseLR) || isa<SymbolicRegion>(BaseRR))
58 return;
59
60 if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
61 if (!BT)
62 BT.reset(
63 new BuiltinBug(this, "Pointer subtraction",
64 "Subtraction of two pointers that do not point to "
65 "the same memory chunk may cause incorrect result."));
66 auto R =
67 std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N);
68 R->addRange(B->getSourceRange());
69 C.emitReport(std::move(R));
70 }
71 }
72
73 void ento::registerPointerSubChecker(CheckerManager &mgr) {
74 mgr.registerChecker<PointerSubChecker>();
75 }
76
77 bool ento::shouldRegisterPointerSubChecker(const LangOptions &LO) {
78 return true;
79 }
ento
clang::BinaryOperator::getOpcode
Opcode getOpcode() const
Definition: Expr.h:3469
BugType.h
Checker.h
CheckerManager.h
clang::LangOptions
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:53
clang::BinaryOperator
A builtin binary operation expression such as "x + y" or "x <= y".
Definition: Expr.h:3434
BuiltinCheckerRegistration.h
clang::BinaryOperator::getLHS
Expr * getLHS() const
Definition: Expr.h:3474
clang
Dataflow Directional Tag Classes.
Definition: CFGReachabilityAnalysis.h:21
clang::Stmt::getSourceRange
SourceRange getSourceRange() const LLVM_READONLY
SourceLocation tokens are not useful in isolation - they are low level value objects created/interpre...
Definition: Stmt.cpp:263
clang::BinaryOperator::getRHS
Expr * getRHS() const
Definition: Expr.h:3476
CheckerContext.h