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
22using namespace clang;
23using namespace ento;
24
25namespace {
26class ArrayBoundChecker :
27 public Checker<check::Location> {
28 const BugType BT{this, "Out-of-bound array access"};
29
30public:
31 void checkLocation(SVal l, bool isLoad, const Stmt* S,
32 CheckerContext &C) const;
33};
34}
35
36void 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>(Val: 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: state, MR: ER->getSuperRegion(), SVB&: C.getSValBuilder(), Ty: ER->getValueType());
60
61 ProgramStateRef StInBound, StOutBound;
62 std::tie(args&: StInBound, args&: StOutBound) = state->assumeInBoundDual(idx: Idx, upperBound: ElementCount);
63 if (StOutBound && !StInBound) {
64 ExplodedNode *N = C.generateErrorNode(State: StOutBound);
65 if (!N)
66 return;
67
68 // FIXME: It would be nice to eventually make this diagnostic more clear,
69 // e.g., by referencing the original declaration or by saying *why* this
70 // reference is outside the range.
71
72 // Generate a report for this bug.
73 auto report = std::make_unique<PathSensitiveBugReport>(
74 args: BT, args: "Access out-of-bound array element (buffer overflow)", args&: N);
75
76 report->addRange(R: LoadS->getSourceRange());
77 C.emitReport(R: std::move(report));
78 return;
79 }
80
81 // Array bound check succeeded. From this point forward the array bound
82 // should always succeed.
83 C.addTransition(State: StInBound);
84}
85
86void ento::registerArrayBoundChecker(CheckerManager &mgr) {
87 mgr.registerChecker<ArrayBoundChecker>();
88}
89
90bool ento::shouldRegisterArrayBoundChecker(const CheckerManager &mgr) {
91 return true;
92}
93