ArrayBoundChecker.cpp revision 390909c89c98ab1807e15e033a72e975f866fb23 
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, const Stmt* S,
31                     CheckerContext &C) const;
32};
33}
34
35void 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 = cast<DefinedOrUnknownSVal>(ER->getIndex());
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  const ProgramState *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  const ProgramState *StInBound = state->assumeInBound(Idx, NumElements, true);
62  const ProgramState *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  assert(StInBound);
88  C.addTransition(StInBound);
89}
90
91void ento::registerArrayBoundChecker(CheckerManager &mgr) {
92  mgr.registerChecker<ArrayBoundChecker>();
93}
94