ArrayBoundChecker.cpp revision e172e8b9e7fc67d7d03589af7e92fe777afcf33a 
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/Checker.h"
17#include "clang/StaticAnalyzer/Core/CheckerManager.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19#include "clang/StaticAnalyzer/Core/BugReporter/BugType.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  mutable llvm::OwningPtr<BuiltinBug> BT;
29public:
30  void checkLocation(SVal l, bool isLoad, CheckerContext &C) const;
31};
32}
33
34void ArrayBoundChecker::checkLocation(SVal l, bool isLoad,
35                                      CheckerContext &C) const {
36  // Check for out of bound array element access.
37  const MemRegion *R = l.getAsRegion();
38  if (!R)
39    return;
40
41  const ElementRegion *ER = dyn_cast<ElementRegion>(R);
42  if (!ER)
43    return;
44
45  // Get the index of the accessed element.
46  DefinedOrUnknownSVal Idx = cast<DefinedOrUnknownSVal>(ER->getIndex());
47
48  // Zero index is always in bound, this also passes ElementRegions created for
49  // pointer casts.
50  if (Idx.isZeroConstant())
51    return;
52
53  const ProgramState *state = C.getState();
54
55  // Get the size of the array.
56  DefinedOrUnknownSVal NumElements
57    = C.getStoreManager().getSizeInElements(state, ER->getSuperRegion(),
58                                            ER->getValueType());
59
60  const ProgramState *StInBound = state->assumeInBound(Idx, NumElements, true);
61  const ProgramState *StOutBound = state->assumeInBound(Idx, NumElements, false);
62  if (StOutBound && !StInBound) {
63    ExplodedNode *N = C.generateSink(StOutBound);
64    if (!N)
65      return;
66
67    if (!BT)
68      BT.reset(new BuiltinBug("Out-of-bound array access",
69                       "Access out-of-bound array element (buffer overflow)"));
70
71    // FIXME: It would be nice to eventually make this diagnostic more clear,
72    // e.g., by referencing the original declaration or by saying *why* this
73    // reference is outside the range.
74
75    // Generate a report for this bug.
76    BugReport *report =
77      new BugReport(*BT, BT->getDescription(), N);
78
79    report->addRange(C.getStmt()->getSourceRange());
80    C.EmitReport(report);
81    return;
82  }
83
84  // Array bound check succeeded.  From this point forward the array bound
85  // should always succeed.
86  assert(StInBound);
87  C.addTransition(StInBound);
88}
89
90void ento::registerArrayBoundChecker(CheckerManager &mgr) {
91  mgr.registerChecker<ArrayBoundChecker>();
92}
93