1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
| //== TestAfterDivZeroChecker.cpp - Test after division by zero checker --*--==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This defines TestAfterDivZeroChecker, a builtin check that performs checks
// for division by zero where the division occurs before comparison with zero.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "llvm/ADT/FoldingSet.h"
using namespace clang;
using namespace ento;
namespace {
class ZeroState {
private:
SymbolRef ZeroSymbol;
unsigned BlockID;
const StackFrameContext *SFC;
public:
ZeroState(SymbolRef S, unsigned B, const StackFrameContext *SFC)
: ZeroSymbol(S), BlockID(B), SFC(SFC) {}
const StackFrameContext *getStackFrameContext() const { return SFC; }
bool operator==(const ZeroState &X) const {
return BlockID == X.BlockID && SFC == X.SFC && ZeroSymbol == X.ZeroSymbol;
}
bool operator<(const ZeroState &X) const {
if (BlockID != X.BlockID)
return BlockID < X.BlockID;
if (SFC != X.SFC)
return SFC < X.SFC;
return ZeroSymbol < X.ZeroSymbol;
}
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.AddInteger(BlockID);
ID.AddPointer(SFC);
ID.AddPointer(ZeroSymbol);
}
};
class DivisionBRVisitor : public BugReporterVisitor {
private:
SymbolRef ZeroSymbol;
const StackFrameContext *SFC;
bool Satisfied;
public:
DivisionBRVisitor(SymbolRef ZeroSymbol, const StackFrameContext *SFC)
: ZeroSymbol(ZeroSymbol), SFC(SFC), Satisfied(false) {}
void Profile(llvm::FoldingSetNodeID &ID) const override {
ID.Add(ZeroSymbol);
ID.Add(SFC);
}
PathDiagnosticPieceRef VisitNode(const ExplodedNode *Succ,
BugReporterContext &BRC,
PathSensitiveBugReport &BR) override;
};
class TestAfterDivZeroChecker
: public Checker<check::PreStmt<BinaryOperator>, check::BranchCondition,
check::EndFunction> {
mutable std::unique_ptr<BuiltinBug> DivZeroBug;
void reportBug(SVal Val, CheckerContext &C) const;
public:
void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
void checkBranchCondition(const Stmt *Condition, CheckerContext &C) const;
void checkEndFunction(const ReturnStmt *RS, CheckerContext &C) const;
void setDivZeroMap(SVal Var, CheckerContext &C) const;
bool hasDivZeroMap(SVal Var, const CheckerContext &C) const;
bool isZero(SVal S, CheckerContext &C) const;
};
} // end anonymous namespace
REGISTER_SET_WITH_PROGRAMSTATE(DivZeroMap, ZeroState)
PathDiagnosticPieceRef
DivisionBRVisitor::VisitNode(const ExplodedNode *Succ, BugReporterContext &BRC,
PathSensitiveBugReport &BR) {
if (Satisfied)
return nullptr;
const Expr *E = nullptr;
if (Optional<PostStmt> P = Succ->getLocationAs<PostStmt>())
if (const BinaryOperator *BO = P->getStmtAs<BinaryOperator>()) {
BinaryOperator::Opcode Op = BO->getOpcode();
if (Op == BO_Div || Op == BO_Rem || Op == BO_DivAssign ||
Op == BO_RemAssign) {
E = BO->getRHS();
}
}
if (!E)
return nullptr;
SVal S = Succ->getSVal(E);
if (ZeroSymbol == S.getAsSymbol() && SFC == Succ->getStackFrame()) {
Satisfied = true;
// Construct a new PathDiagnosticPiece.
ProgramPoint P = Succ->getLocation();
PathDiagnosticLocation L =
PathDiagnosticLocation::create(P, BRC.getSourceManager());
if (!L.isValid() || !L.asLocation().isValid())
return nullptr;
return std::make_shared<PathDiagnosticEventPiece>(
L, "Division with compared value made here");
}
return nullptr;
}
bool TestAfterDivZeroChecker::isZero(SVal S, CheckerContext &C) const {
Optional<DefinedSVal> DSV = S.getAs<DefinedSVal>();
if (!DSV)
return false;
ConstraintManager &CM = C.getConstraintManager();
return !CM.assume(C.getState(), *DSV, true);
}
void TestAfterDivZeroChecker::setDivZeroMap(SVal Var, CheckerContext &C) const {
SymbolRef SR = Var.getAsSymbol();
if (!SR)
return;
ProgramStateRef State = C.getState();
State =
State->add<DivZeroMap>(ZeroState(SR, C.getBlockID(), C.getStackFrame()));
C.addTransition(State);
}
bool TestAfterDivZeroChecker::hasDivZeroMap(SVal Var,
const CheckerContext &C) const {
SymbolRef SR = Var.getAsSymbol();
if (!SR)
return false;
ZeroState ZS(SR, C.getBlockID(), C.getStackFrame());
return C.getState()->contains<DivZeroMap>(ZS);
}
void TestAfterDivZeroChecker::reportBug(SVal Val, CheckerContext &C) const {
if (ExplodedNode *N = C.generateErrorNode(C.getState())) {
if (!DivZeroBug)
DivZeroBug.reset(new BuiltinBug(this, "Division by zero"));
auto R = std::make_unique<PathSensitiveBugReport>(
*DivZeroBug, "Value being compared against zero has already been used "
"for division",
N);
R->addVisitor(std::make_unique<DivisionBRVisitor>(Val.getAsSymbol(),
C.getStackFrame()));
C.emitReport(std::move(R));
}
}
void TestAfterDivZeroChecker::checkEndFunction(const ReturnStmt *,
CheckerContext &C) const {
ProgramStateRef State = C.getState();
DivZeroMapTy DivZeroes = State->get<DivZeroMap>();
if (DivZeroes.isEmpty())
return;
DivZeroMapTy::Factory &F = State->get_context<DivZeroMap>();
for (llvm::ImmutableSet<ZeroState>::iterator I = DivZeroes.begin(),
E = DivZeroes.end();
I != E; ++I) {
ZeroState ZS = *I;
if (ZS.getStackFrameContext() == C.getStackFrame())
DivZeroes = F.remove(DivZeroes, ZS);
}
C.addTransition(State->set<DivZeroMap>(DivZeroes));
}
void TestAfterDivZeroChecker::checkPreStmt(const BinaryOperator *B,
CheckerContext &C) const {
BinaryOperator::Opcode Op = B->getOpcode();
if (Op == BO_Div || Op == BO_Rem || Op == BO_DivAssign ||
Op == BO_RemAssign) {
SVal S = C.getSVal(B->getRHS());
if (!isZero(S, C))
setDivZeroMap(S, C);
}
}
void TestAfterDivZeroChecker::checkBranchCondition(const Stmt *Condition,
CheckerContext &C) const {
if (const BinaryOperator *B = dyn_cast<BinaryOperator>(Condition)) {
if (B->isComparisonOp()) {
const IntegerLiteral *IntLiteral = dyn_cast<IntegerLiteral>(B->getRHS());
bool LRHS = true;
if (!IntLiteral) {
IntLiteral = dyn_cast<IntegerLiteral>(B->getLHS());
LRHS = false;
}
if (!IntLiteral || IntLiteral->getValue() != 0)
return;
SVal Val = C.getSVal(LRHS ? B->getLHS() : B->getRHS());
if (hasDivZeroMap(Val, C))
reportBug(Val, C);
}
} else if (const UnaryOperator *U = dyn_cast<UnaryOperator>(Condition)) {
if (U->getOpcode() == UO_LNot) {
SVal Val;
if (const ImplicitCastExpr *I =
dyn_cast<ImplicitCastExpr>(U->getSubExpr()))
Val = C.getSVal(I->getSubExpr());
if (hasDivZeroMap(Val, C))
reportBug(Val, C);
else {
Val = C.getSVal(U->getSubExpr());
if (hasDivZeroMap(Val, C))
reportBug(Val, C);
}
}
} else if (const ImplicitCastExpr *IE =
dyn_cast<ImplicitCastExpr>(Condition)) {
SVal Val = C.getSVal(IE->getSubExpr());
if (hasDivZeroMap(Val, C))
reportBug(Val, C);
else {
SVal Val = C.getSVal(Condition);
if (hasDivZeroMap(Val, C))
reportBug(Val, C);
}
}
}
void ento::registerTestAfterDivZeroChecker(CheckerManager &mgr) {
mgr.registerChecker<TestAfterDivZeroChecker>();
}
bool ento::shouldRegisterTestAfterDivZeroChecker(const LangOptions &LO) {
return true;
}
|