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
|
//== DivZeroChecker.cpp - Division by zero checker --------------*- C++ -*--==//
//
// 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 DivZeroChecker, a builtin check in ExprEngine that performs
// checks for division by zeros.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Checkers/Taint.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/BugReporter/CommonBugCategories.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include <optional>
using namespace clang;
using namespace ento;
using namespace taint;
namespace {
class DivZeroChecker : public CheckerFamily<check::PreStmt<BinaryOperator>> {
void reportBug(StringRef Msg, ProgramStateRef StateZero,
CheckerContext &C) const;
void reportTaintBug(StringRef Msg, ProgramStateRef StateZero,
CheckerContext &C,
llvm::ArrayRef<SymbolRef> TaintedSyms) const;
public:
/// This checker family implements two user-facing checker parts.
CheckerFrontendWithBugType DivideZeroChecker{"Division by zero"};
CheckerFrontendWithBugType TaintedDivChecker{"Division by zero",
categories::TaintedData};
void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
/// Identifies this checker family for debugging purposes.
StringRef getDebugTag() const override { return "DivZeroChecker"; }
};
} // end anonymous namespace
static const Expr *getDenomExpr(const ExplodedNode *N) {
const Stmt *S = N->getLocationAs<PreStmt>()->getStmt();
if (const auto *BE = dyn_cast<BinaryOperator>(S))
return BE->getRHS();
return nullptr;
}
void DivZeroChecker::reportBug(StringRef Msg, ProgramStateRef StateZero,
CheckerContext &C) const {
if (!DivideZeroChecker.isEnabled())
return;
if (ExplodedNode *N = C.generateErrorNode(StateZero)) {
auto R =
std::make_unique<PathSensitiveBugReport>(DivideZeroChecker, Msg, N);
bugreporter::trackExpressionValue(N, getDenomExpr(N), *R);
C.emitReport(std::move(R));
}
}
void DivZeroChecker::reportTaintBug(
StringRef Msg, ProgramStateRef StateZero, CheckerContext &C,
llvm::ArrayRef<SymbolRef> TaintedSyms) const {
if (!TaintedDivChecker.isEnabled())
return;
if (ExplodedNode *N = C.generateErrorNode(StateZero)) {
auto R =
std::make_unique<PathSensitiveBugReport>(TaintedDivChecker, Msg, N);
bugreporter::trackExpressionValue(N, getDenomExpr(N), *R);
for (auto Sym : TaintedSyms)
R->markInteresting(Sym);
C.emitReport(std::move(R));
}
}
void DivZeroChecker::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)
return;
if (!B->getRHS()->getType()->isScalarType())
return;
SVal Denom = C.getSVal(B->getRHS());
std::optional<DefinedSVal> DV = Denom.getAs<DefinedSVal>();
// Divide-by-undefined handled in the generic checking for uses of
// undefined values.
if (!DV)
return;
// Check for divide by zero.
ConstraintManager &CM = C.getConstraintManager();
ProgramStateRef stateNotZero, stateZero;
std::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV);
if (!stateNotZero) {
assert(stateZero);
reportBug("Division by zero", stateZero, C);
return;
}
if ((stateNotZero && stateZero)) {
std::vector<SymbolRef> taintedSyms = getTaintedSymbols(C.getState(), *DV);
if (!taintedSyms.empty()) {
reportTaintBug("Division by a tainted value, possibly zero", stateZero, C,
taintedSyms);
// Fallthrough to continue analysis in case of non-zero denominator.
}
}
// If we get here, then the denom should not be zero. We abandon the implicit
// zero denom case for now.
C.addTransition(stateNotZero);
}
void ento::registerDivZeroChecker(CheckerManager &Mgr) {
Mgr.getChecker<DivZeroChecker>()->DivideZeroChecker.enable(Mgr);
}
bool ento::shouldRegisterDivZeroChecker(const CheckerManager &) { return true; }
void ento::registerTaintedDivChecker(CheckerManager &Mgr) {
Mgr.getChecker<DivZeroChecker>()->TaintedDivChecker.enable(Mgr);
}
bool ento::shouldRegisterTaintedDivChecker(const CheckerManager &) {
return true;
}
|
