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//===- ObjCAutoreleaseWriteChecker.cpp ----------------------------*- 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 file defines ObjCAutoreleaseWriteChecker which warns against writes
// into autoreleased out parameters which cause crashes.
// An example of a problematic write is a write to {@code error} in the example
// below:
//
// - (BOOL) mymethod:(NSError *__autoreleasing *)error list:(NSArray*) list {
// [list enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
// NSString *myString = obj;
// if ([myString isEqualToString:@"error"] && error)
// *error = [NSError errorWithDomain:@"MyDomain" code:-1];
// }];
// return false;
// }
//
// Such code will crash on read from `*error` due to the autorelease pool
// in `enumerateObjectsUsingBlock` implementation freeing the error object
// on exit from the function.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
#include "llvm/ADT/Twine.h"
using namespace clang;
using namespace ento;
using namespace ast_matchers;
namespace {
const char *ProblematicWriteBind = "problematicwrite";
const char *CapturedBind = "capturedbind";
const char *ParamBind = "parambind";
const char *IsMethodBind = "ismethodbind";
class ObjCAutoreleaseWriteChecker : public Checker<check::ASTCodeBody> {
public:
void checkASTCodeBody(const Decl *D,
AnalysisManager &AM,
BugReporter &BR) const;
private:
std::vector<std::string> SelectorsWithAutoreleasingPool = {
// Common to NSArray, NSSet, NSOrderedSet
"enumerateObjectsUsingBlock:",
"enumerateObjectsWithOptions:usingBlock:",
// Common to NSArray and NSOrderedSet
"enumerateObjectsAtIndexes:options:usingBlock:",
"indexOfObjectAtIndexes:options:passingTest:",
"indexesOfObjectsAtIndexes:options:passingTest:",
"indexOfObjectPassingTest:",
"indexOfObjectWithOptions:passingTest:",
"indexesOfObjectsPassingTest:",
"indexesOfObjectsWithOptions:passingTest:",
// NSDictionary
"enumerateKeysAndObjectsUsingBlock:",
"enumerateKeysAndObjectsWithOptions:usingBlock:",
"keysOfEntriesPassingTest:",
"keysOfEntriesWithOptions:passingTest:",
// NSSet
"objectsPassingTest:",
"objectsWithOptions:passingTest:",
"enumerateIndexPathsWithOptions:usingBlock:",
// NSIndexSet
"enumerateIndexesWithOptions:usingBlock:",
"enumerateIndexesUsingBlock:",
"enumerateIndexesInRange:options:usingBlock:",
"enumerateRangesUsingBlock:",
"enumerateRangesWithOptions:usingBlock:",
"enumerateRangesInRange:options:usingBlock:",
"indexPassingTest:",
"indexesPassingTest:",
"indexWithOptions:passingTest:",
"indexesWithOptions:passingTest:",
"indexInRange:options:passingTest:",
"indexesInRange:options:passingTest:"
};
std::vector<std::string> FunctionsWithAutoreleasingPool = {
"dispatch_async", "dispatch_group_async", "dispatch_barrier_async"};
};
}
static inline std::vector<llvm::StringRef> toRefs(std::vector<std::string> V) {
return std::vector<llvm::StringRef>(V.begin(), V.end());
}
static auto callsNames(std::vector<std::string> FunctionNames)
-> decltype(callee(functionDecl())) {
return callee(functionDecl(hasAnyName(toRefs(FunctionNames))));
}
static void emitDiagnostics(BoundNodes &Match, const Decl *D, BugReporter &BR,
AnalysisManager &AM,
const ObjCAutoreleaseWriteChecker *Checker) {
AnalysisDeclContext *ADC = AM.getAnalysisDeclContext(D);
const auto *PVD = Match.getNodeAs<ParmVarDecl>(ParamBind);
QualType Ty = PVD->getType();
if (Ty->getPointeeType().getObjCLifetime() != Qualifiers::OCL_Autoreleasing)
return;
const char *ActionMsg = "Write to";
const auto *MarkedStmt = Match.getNodeAs<Expr>(ProblematicWriteBind);
bool IsCapture = false;
// Prefer to warn on write, but if not available, warn on capture.
if (!MarkedStmt) {
MarkedStmt = Match.getNodeAs<Expr>(CapturedBind);
assert(MarkedStmt);
ActionMsg = "Capture of";
IsCapture = true;
}
SourceRange Range = MarkedStmt->getSourceRange();
PathDiagnosticLocation Location = PathDiagnosticLocation::createBegin(
MarkedStmt, BR.getSourceManager(), ADC);
bool IsMethod = Match.getNodeAs<ObjCMethodDecl>(IsMethodBind) != nullptr;
const char *Name = IsMethod ? "method" : "function";
BR.EmitBasicReport(
ADC->getDecl(), Checker,
/*Name=*/(llvm::Twine(ActionMsg)
+ " autoreleasing out parameter inside autorelease pool").str(),
/*Category=*/"Memory",
(llvm::Twine(ActionMsg) + " autoreleasing out parameter " +
(IsCapture ? "'" + PVD->getName() + "'" + " " : "") + "inside " +
"autorelease pool that may exit before " + Name + " returns; consider "
"writing first to a strong local variable declared outside of the block")
.str(),
Location,
Range);
}
void ObjCAutoreleaseWriteChecker::checkASTCodeBody(const Decl *D,
AnalysisManager &AM,
BugReporter &BR) const {
auto DoublePointerParamM =
parmVarDecl(hasType(hasCanonicalType(pointerType(
pointee(hasCanonicalType(objcObjectPointerType()))))))
.bind(ParamBind);
auto ReferencedParamM =
declRefExpr(to(parmVarDecl(DoublePointerParamM))).bind(CapturedBind);
// Write into a binded object, e.g. *ParamBind = X.
auto WritesIntoM = binaryOperator(
hasLHS(unaryOperator(
hasOperatorName("*"),
hasUnaryOperand(
ignoringParenImpCasts(ReferencedParamM))
)),
hasOperatorName("=")
).bind(ProblematicWriteBind);
auto ArgumentCaptureM = hasAnyArgument(
ignoringParenImpCasts(ReferencedParamM));
auto CapturedInParamM = stmt(anyOf(
callExpr(ArgumentCaptureM),
objcMessageExpr(ArgumentCaptureM)));
// WritesIntoM happens inside a block passed as an argument.
auto WritesOrCapturesInBlockM = hasAnyArgument(allOf(
hasType(hasCanonicalType(blockPointerType())),
forEachDescendant(
stmt(anyOf(WritesIntoM, CapturedInParamM))
)));
auto BlockPassedToMarkedFuncM = stmt(anyOf(
callExpr(allOf(
callsNames(FunctionsWithAutoreleasingPool), WritesOrCapturesInBlockM)),
objcMessageExpr(allOf(
hasAnySelector(toRefs(SelectorsWithAutoreleasingPool)),
WritesOrCapturesInBlockM))
));
auto HasParamAndWritesInMarkedFuncM = allOf(
hasAnyParameter(DoublePointerParamM),
forEachDescendant(BlockPassedToMarkedFuncM));
auto MatcherM = decl(anyOf(
objcMethodDecl(HasParamAndWritesInMarkedFuncM).bind(IsMethodBind),
functionDecl(HasParamAndWritesInMarkedFuncM),
blockDecl(HasParamAndWritesInMarkedFuncM)));
auto Matches = match(MatcherM, *D, AM.getASTContext());
for (BoundNodes Match : Matches)
emitDiagnostics(Match, D, BR, AM, this);
}
void ento::registerAutoreleaseWriteChecker(CheckerManager &Mgr) {
Mgr.registerChecker<ObjCAutoreleaseWriteChecker>();
}
bool ento::shouldRegisterAutoreleaseWriteChecker(const LangOptions &LO) {
return true;
}
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