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
|
//=== StackAddrEscapeChecker.cpp ----------------------------------*- C++ -*--//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines stack address leak checker, which checks if an invalid
// stack address is stored into a global or heap location. See CERT DCL30-C.
//
//===----------------------------------------------------------------------===//
#include "ClangSACheckers.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/GRState.h"
#include "clang/Basic/SourceManager.h"
#include "llvm/ADT/SmallString.h"
using namespace clang;
using namespace ento;
namespace {
class StackAddrEscapeChecker : public Checker< check::PreStmt<ReturnStmt>,
check::EndPath > {
mutable llvm::OwningPtr<BuiltinBug> BT_stackleak;
mutable llvm::OwningPtr<BuiltinBug> BT_returnstack;
public:
void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const;
void checkEndPath(EndOfFunctionNodeBuilder &B, ExprEngine &Eng) const;
private:
void EmitStackError(CheckerContext &C, const MemRegion *R,
const Expr *RetE) const;
static SourceRange GenName(llvm::raw_ostream &os, const MemRegion *R,
SourceManager &SM);
};
}
SourceRange StackAddrEscapeChecker::GenName(llvm::raw_ostream &os,
const MemRegion *R,
SourceManager &SM) {
// Get the base region, stripping away fields and elements.
R = R->getBaseRegion();
SourceRange range;
os << "Address of ";
// Check if the region is a compound literal.
if (const CompoundLiteralRegion* CR = dyn_cast<CompoundLiteralRegion>(R)) {
const CompoundLiteralExpr* CL = CR->getLiteralExpr();
os << "stack memory associated with a compound literal "
"declared on line "
<< SM.getInstantiationLineNumber(CL->getLocStart())
<< " returned to caller";
range = CL->getSourceRange();
}
else if (const AllocaRegion* AR = dyn_cast<AllocaRegion>(R)) {
const Expr* ARE = AR->getExpr();
SourceLocation L = ARE->getLocStart();
range = ARE->getSourceRange();
os << "stack memory allocated by call to alloca() on line "
<< SM.getInstantiationLineNumber(L);
}
else if (const BlockDataRegion *BR = dyn_cast<BlockDataRegion>(R)) {
const BlockDecl *BD = BR->getCodeRegion()->getDecl();
SourceLocation L = BD->getLocStart();
range = BD->getSourceRange();
os << "stack-allocated block declared on line "
<< SM.getInstantiationLineNumber(L);
}
else if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
os << "stack memory associated with local variable '"
<< VR->getString() << '\'';
range = VR->getDecl()->getSourceRange();
}
else {
assert(false && "Invalid region in ReturnStackAddressChecker.");
}
return range;
}
void StackAddrEscapeChecker::EmitStackError(CheckerContext &C, const MemRegion *R,
const Expr *RetE) const {
ExplodedNode *N = C.generateSink();
if (!N)
return;
if (!BT_returnstack)
BT_returnstack.reset(
new BuiltinBug("Return of address to stack-allocated memory"));
// Generate a report for this bug.
llvm::SmallString<512> buf;
llvm::raw_svector_ostream os(buf);
SourceRange range = GenName(os, R, C.getSourceManager());
os << " returned to caller";
RangedBugReport *report = new RangedBugReport(*BT_returnstack, os.str(), N);
report->addRange(RetE->getSourceRange());
if (range.isValid())
report->addRange(range);
C.EmitReport(report);
}
void StackAddrEscapeChecker::checkPreStmt(const ReturnStmt *RS,
CheckerContext &C) const {
const Expr *RetE = RS->getRetValue();
if (!RetE)
return;
SVal V = C.getState()->getSVal(RetE);
const MemRegion *R = V.getAsRegion();
if (!R || !R->hasStackStorage())
return;
if (R->hasStackStorage()) {
// Automatic reference counting automatically copies blocks.
if (C.getASTContext().getLangOptions().ObjCAutoRefCount &&
isa<BlockDataRegion>(R))
return;
EmitStackError(C, R, RetE);
return;
}
}
void StackAddrEscapeChecker::checkEndPath(EndOfFunctionNodeBuilder &B,
ExprEngine &Eng) const {
const GRState *state = B.getState();
// Iterate over all bindings to global variables and see if it contains
// a memory region in the stack space.
class CallBack : public StoreManager::BindingsHandler {
private:
ExprEngine &Eng;
const StackFrameContext *CurSFC;
public:
llvm::SmallVector<std::pair<const MemRegion*, const MemRegion*>, 10> V;
CallBack(ExprEngine &Eng, const LocationContext *LCtx)
: Eng(Eng), CurSFC(LCtx->getCurrentStackFrame()) {}
bool HandleBinding(StoreManager &SMgr, Store store,
const MemRegion *region, SVal val) {
if (!isa<GlobalsSpaceRegion>(region->getMemorySpace()))
return true;
const MemRegion *vR = val.getAsRegion();
if (!vR)
return true;
// Under automated retain release, it is okay to assign a block
// directly to a global variable.
if (Eng.getContext().getLangOptions().ObjCAutoRefCount &&
isa<BlockDataRegion>(vR))
return true;
if (const StackSpaceRegion *SSR =
dyn_cast<StackSpaceRegion>(vR->getMemorySpace())) {
// If the global variable holds a location in the current stack frame,
// record the binding to emit a warning.
if (SSR->getStackFrame() == CurSFC)
V.push_back(std::make_pair(region, vR));
}
return true;
}
};
CallBack cb(Eng, B.getPredecessor()->getLocationContext());
state->getStateManager().getStoreManager().iterBindings(state->getStore(),cb);
if (cb.V.empty())
return;
// Generate an error node.
ExplodedNode *N = B.generateNode(state);
if (!N)
return;
if (!BT_stackleak)
BT_stackleak.reset(
new BuiltinBug("Stack address stored into global variable",
"Stack address was saved into a global variable. "
"This is dangerous because the address will become "
"invalid after returning from the function"));
for (unsigned i = 0, e = cb.V.size(); i != e; ++i) {
// Generate a report for this bug.
llvm::SmallString<512> buf;
llvm::raw_svector_ostream os(buf);
SourceRange range = GenName(os, cb.V[i].second,
Eng.getContext().getSourceManager());
os << " is still referred to by the global variable '";
const VarRegion *VR = cast<VarRegion>(cb.V[i].first->getBaseRegion());
os << VR->getDecl()->getNameAsString()
<< "' upon returning to the caller. This will be a dangling reference";
RangedBugReport *report = new RangedBugReport(*BT_stackleak, os.str(), N);
if (range.isValid())
report->addRange(range);
Eng.getBugReporter().EmitReport(report);
}
}
void ento::registerStackAddrEscapeChecker(CheckerManager &mgr) {
mgr.registerChecker<StackAddrEscapeChecker>();
}
|
