1 //== ArrayBoundChecker.cpp ------------------------------*- C++ -*--==//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines ArrayBoundChecker, which is a path-sensitive check
11 // which looks for an out-of-bound array element access.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "ClangSACheckers.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 "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
21
22 using namespace clang;
23 using namespace ento;
24
25 namespace {
26 class ArrayBoundChecker :
27 public Checker<check::Location> {
28 mutable OwningPtr<BuiltinBug> BT;
29 public:
30 void checkLocation(SVal l, bool isLoad, const Stmt* S,
31 CheckerContext &C) const;
32 };
33 }
34
checkLocation(SVal l,bool isLoad,const Stmt * LoadS,CheckerContext & C) const35 void ArrayBoundChecker::checkLocation(SVal l, bool isLoad, const Stmt* LoadS,
36 CheckerContext &C) const {
37 // Check for out of bound array element access.
38 const MemRegion *R = l.getAsRegion();
39 if (!R)
40 return;
41
42 const ElementRegion *ER = dyn_cast<ElementRegion>(R);
43 if (!ER)
44 return;
45
46 // Get the index of the accessed element.
47 DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>();
48
49 // Zero index is always in bound, this also passes ElementRegions created for
50 // pointer casts.
51 if (Idx.isZeroConstant())
52 return;
53
54 ProgramStateRef state = C.getState();
55
56 // Get the size of the array.
57 DefinedOrUnknownSVal NumElements
58 = C.getStoreManager().getSizeInElements(state, ER->getSuperRegion(),
59 ER->getValueType());
60
61 ProgramStateRef StInBound = state->assumeInBound(Idx, NumElements, true);
62 ProgramStateRef StOutBound = state->assumeInBound(Idx, NumElements, false);
63 if (StOutBound && !StInBound) {
64 ExplodedNode *N = C.generateSink(StOutBound);
65 if (!N)
66 return;
67
68 if (!BT)
69 BT.reset(new BuiltinBug("Out-of-bound array access",
70 "Access out-of-bound array element (buffer overflow)"));
71
72 // FIXME: It would be nice to eventually make this diagnostic more clear,
73 // e.g., by referencing the original declaration or by saying *why* this
74 // reference is outside the range.
75
76 // Generate a report for this bug.
77 BugReport *report =
78 new BugReport(*BT, BT->getDescription(), N);
79
80 report->addRange(LoadS->getSourceRange());
81 C.emitReport(report);
82 return;
83 }
84
85 // Array bound check succeeded. From this point forward the array bound
86 // should always succeed.
87 C.addTransition(StInBound);
88 }
89
registerArrayBoundChecker(CheckerManager & mgr)90 void ento::registerArrayBoundChecker(CheckerManager &mgr) {
91 mgr.registerChecker<ArrayBoundChecker>();
92 }
93