1 //===- ObjCAutoreleaseWriteChecker.cpp ----------------------------*- C++ -*-==//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defines ObjCAutoreleaseWriteChecker which warns against writes
10 // into autoreleased out parameters which cause crashes.
11 // An example of a problematic write is a write to @c error in the example
12 // below:
13 //
14 // - (BOOL) mymethod:(NSError *__autoreleasing *)error list:(NSArray*) list {
15 // [list enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
16 // NSString *myString = obj;
17 // if ([myString isEqualToString:@"error"] && error)
18 // *error = [NSError errorWithDomain:@"MyDomain" code:-1];
19 // }];
20 // return false;
21 // }
22 //
23 // Such code will crash on read from `*error` due to the autorelease pool
24 // in `enumerateObjectsUsingBlock` implementation freeing the error object
25 // on exit from the function.
26 //
27 //===----------------------------------------------------------------------===//
28
29 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
30 #include "clang/ASTMatchers/ASTMatchFinder.h"
31 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
32 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
33 #include "clang/StaticAnalyzer/Core/BugReporter/CommonBugCategories.h"
34 #include "clang/StaticAnalyzer/Core/Checker.h"
35 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
36 #include "llvm/ADT/Twine.h"
37
38 using namespace clang;
39 using namespace ento;
40 using namespace ast_matchers;
41
42 namespace {
43
44 const char *ProblematicWriteBind = "problematicwrite";
45 const char *CapturedBind = "capturedbind";
46 const char *ParamBind = "parambind";
47 const char *IsMethodBind = "ismethodbind";
48 const char *IsARPBind = "isautoreleasepoolbind";
49
50 class ObjCAutoreleaseWriteChecker : public Checker<check::ASTCodeBody> {
51 public:
52 void checkASTCodeBody(const Decl *D,
53 AnalysisManager &AM,
54 BugReporter &BR) const;
55 private:
56 std::vector<std::string> SelectorsWithAutoreleasingPool = {
57 // Common to NSArray, NSSet, NSOrderedSet
58 "enumerateObjectsUsingBlock:",
59 "enumerateObjectsWithOptions:usingBlock:",
60
61 // Common to NSArray and NSOrderedSet
62 "enumerateObjectsAtIndexes:options:usingBlock:",
63 "indexOfObjectAtIndexes:options:passingTest:",
64 "indexesOfObjectsAtIndexes:options:passingTest:",
65 "indexOfObjectPassingTest:",
66 "indexOfObjectWithOptions:passingTest:",
67 "indexesOfObjectsPassingTest:",
68 "indexesOfObjectsWithOptions:passingTest:",
69
70 // NSDictionary
71 "enumerateKeysAndObjectsUsingBlock:",
72 "enumerateKeysAndObjectsWithOptions:usingBlock:",
73 "keysOfEntriesPassingTest:",
74 "keysOfEntriesWithOptions:passingTest:",
75
76 // NSSet
77 "objectsPassingTest:",
78 "objectsWithOptions:passingTest:",
79 "enumerateIndexPathsWithOptions:usingBlock:",
80
81 // NSIndexSet
82 "enumerateIndexesWithOptions:usingBlock:",
83 "enumerateIndexesUsingBlock:",
84 "enumerateIndexesInRange:options:usingBlock:",
85 "enumerateRangesUsingBlock:",
86 "enumerateRangesWithOptions:usingBlock:",
87 "enumerateRangesInRange:options:usingBlock:",
88 "indexPassingTest:",
89 "indexesPassingTest:",
90 "indexWithOptions:passingTest:",
91 "indexesWithOptions:passingTest:",
92 "indexInRange:options:passingTest:",
93 "indexesInRange:options:passingTest:"
94 };
95
96 std::vector<std::string> FunctionsWithAutoreleasingPool = {
97 "dispatch_async", "dispatch_group_async", "dispatch_barrier_async"};
98 };
99 }
100
101 static inline std::vector<llvm::StringRef>
toRefs(const std::vector<std::string> & V)102 toRefs(const std::vector<std::string> &V) {
103 return std::vector<llvm::StringRef>(V.begin(), V.end());
104 }
105
106 static decltype(auto)
callsNames(const std::vector<std::string> & FunctionNames)107 callsNames(const std::vector<std::string> &FunctionNames) {
108 return callee(functionDecl(hasAnyName(toRefs(FunctionNames))));
109 }
110
emitDiagnostics(BoundNodes & Match,const Decl * D,BugReporter & BR,AnalysisManager & AM,const ObjCAutoreleaseWriteChecker * Checker)111 static void emitDiagnostics(BoundNodes &Match, const Decl *D, BugReporter &BR,
112 AnalysisManager &AM,
113 const ObjCAutoreleaseWriteChecker *Checker) {
114 AnalysisDeclContext *ADC = AM.getAnalysisDeclContext(D);
115
116 const auto *PVD = Match.getNodeAs<ParmVarDecl>(ParamBind);
117 QualType Ty = PVD->getType();
118 if (Ty->getPointeeType().getObjCLifetime() != Qualifiers::OCL_Autoreleasing)
119 return;
120 const char *ActionMsg = "Write to";
121 const auto *MarkedStmt = Match.getNodeAs<Expr>(ProblematicWriteBind);
122 bool IsCapture = false;
123
124 // Prefer to warn on write, but if not available, warn on capture.
125 if (!MarkedStmt) {
126 MarkedStmt = Match.getNodeAs<Expr>(CapturedBind);
127 assert(MarkedStmt);
128 ActionMsg = "Capture of";
129 IsCapture = true;
130 }
131
132 SourceRange Range = MarkedStmt->getSourceRange();
133 PathDiagnosticLocation Location = PathDiagnosticLocation::createBegin(
134 MarkedStmt, BR.getSourceManager(), ADC);
135
136 bool IsMethod = Match.getNodeAs<ObjCMethodDecl>(IsMethodBind) != nullptr;
137 const char *FunctionDescription = IsMethod ? "method" : "function";
138 bool IsARP = Match.getNodeAs<ObjCAutoreleasePoolStmt>(IsARPBind) != nullptr;
139
140 llvm::SmallString<128> BugNameBuf;
141 llvm::raw_svector_ostream BugName(BugNameBuf);
142 BugName << ActionMsg
143 << " autoreleasing out parameter inside autorelease pool";
144
145 llvm::SmallString<128> BugMessageBuf;
146 llvm::raw_svector_ostream BugMessage(BugMessageBuf);
147 BugMessage << ActionMsg << " autoreleasing out parameter ";
148 if (IsCapture)
149 BugMessage << "'" + PVD->getName() + "' ";
150
151 BugMessage << "inside ";
152 if (IsARP)
153 BugMessage << "locally-scoped autorelease pool;";
154 else
155 BugMessage << "autorelease pool that may exit before "
156 << FunctionDescription << " returns;";
157
158 BugMessage << " consider writing first to a strong local variable"
159 " declared outside ";
160 if (IsARP)
161 BugMessage << "of the autorelease pool";
162 else
163 BugMessage << "of the block";
164
165 BR.EmitBasicReport(ADC->getDecl(), Checker, BugName.str(),
166 categories::MemoryRefCount, BugMessage.str(), Location,
167 Range);
168 }
169
checkASTCodeBody(const Decl * D,AnalysisManager & AM,BugReporter & BR) const170 void ObjCAutoreleaseWriteChecker::checkASTCodeBody(const Decl *D,
171 AnalysisManager &AM,
172 BugReporter &BR) const {
173
174 auto DoublePointerParamM =
175 parmVarDecl(hasType(hasCanonicalType(pointerType(
176 pointee(hasCanonicalType(objcObjectPointerType()))))))
177 .bind(ParamBind);
178
179 auto ReferencedParamM =
180 declRefExpr(to(parmVarDecl(DoublePointerParamM))).bind(CapturedBind);
181
182 // Write into a binded object, e.g. *ParamBind = X.
183 auto WritesIntoM = binaryOperator(
184 hasLHS(unaryOperator(
185 hasOperatorName("*"),
186 hasUnaryOperand(
187 ignoringParenImpCasts(ReferencedParamM))
188 )),
189 hasOperatorName("=")
190 ).bind(ProblematicWriteBind);
191
192 auto ArgumentCaptureM = hasAnyArgument(
193 ignoringParenImpCasts(ReferencedParamM));
194 auto CapturedInParamM = stmt(anyOf(
195 callExpr(ArgumentCaptureM),
196 objcMessageExpr(ArgumentCaptureM)));
197
198 // WritesIntoM happens inside a block passed as an argument.
199 auto WritesOrCapturesInBlockM = hasAnyArgument(allOf(
200 hasType(hasCanonicalType(blockPointerType())),
201 forEachDescendant(
202 stmt(anyOf(WritesIntoM, CapturedInParamM))
203 )));
204
205 auto BlockPassedToMarkedFuncM = stmt(anyOf(
206 callExpr(allOf(
207 callsNames(FunctionsWithAutoreleasingPool), WritesOrCapturesInBlockM)),
208 objcMessageExpr(allOf(
209 hasAnySelector(toRefs(SelectorsWithAutoreleasingPool)),
210 WritesOrCapturesInBlockM))
211 ));
212
213 // WritesIntoM happens inside an explicit @autoreleasepool.
214 auto WritesOrCapturesInPoolM =
215 autoreleasePoolStmt(
216 forEachDescendant(stmt(anyOf(WritesIntoM, CapturedInParamM))))
217 .bind(IsARPBind);
218
219 auto HasParamAndWritesInMarkedFuncM =
220 allOf(hasAnyParameter(DoublePointerParamM),
221 anyOf(forEachDescendant(BlockPassedToMarkedFuncM),
222 forEachDescendant(WritesOrCapturesInPoolM)));
223
224 auto MatcherM = decl(anyOf(
225 objcMethodDecl(HasParamAndWritesInMarkedFuncM).bind(IsMethodBind),
226 functionDecl(HasParamAndWritesInMarkedFuncM),
227 blockDecl(HasParamAndWritesInMarkedFuncM)));
228
229 auto Matches = match(MatcherM, *D, AM.getASTContext());
230 for (BoundNodes Match : Matches)
231 emitDiagnostics(Match, D, BR, AM, this);
232 }
233
registerAutoreleaseWriteChecker(CheckerManager & Mgr)234 void ento::registerAutoreleaseWriteChecker(CheckerManager &Mgr) {
235 Mgr.registerChecker<ObjCAutoreleaseWriteChecker>();
236 }
237
shouldRegisterAutoreleaseWriteChecker(const CheckerManager & mgr)238 bool ento::shouldRegisterAutoreleaseWriteChecker(const CheckerManager &mgr) {
239 return true;
240 }
241