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389 lines
15 KiB
389 lines
15 KiB
//=== StackAddrEscapeChecker.cpp ----------------------------------*- C++ -*--//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines stack address leak checker, which checks if an invalid
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// stack address is stored into a global or heap location. See CERT DCL30-C.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
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#include "clang/AST/ExprCXX.h"
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#include "clang/Basic/SourceManager.h"
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#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace clang;
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using namespace ento;
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namespace {
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class StackAddrEscapeChecker
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: public Checker<check::PreCall, check::PreStmt<ReturnStmt>,
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check::EndFunction> {
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mutable IdentifierInfo *dispatch_semaphore_tII;
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mutable std::unique_ptr<BuiltinBug> BT_stackleak;
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mutable std::unique_ptr<BuiltinBug> BT_returnstack;
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mutable std::unique_ptr<BuiltinBug> BT_capturedstackasync;
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mutable std::unique_ptr<BuiltinBug> BT_capturedstackret;
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public:
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enum CheckKind {
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CK_StackAddrEscapeChecker,
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CK_StackAddrAsyncEscapeChecker,
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CK_NumCheckKinds
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};
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DefaultBool ChecksEnabled[CK_NumCheckKinds];
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CheckerNameRef CheckNames[CK_NumCheckKinds];
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void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
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void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const;
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void checkEndFunction(const ReturnStmt *RS, CheckerContext &Ctx) const;
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private:
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void checkReturnedBlockCaptures(const BlockDataRegion &B,
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CheckerContext &C) const;
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void checkAsyncExecutedBlockCaptures(const BlockDataRegion &B,
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CheckerContext &C) const;
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void EmitStackError(CheckerContext &C, const MemRegion *R,
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const Expr *RetE) const;
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bool isSemaphoreCaptured(const BlockDecl &B) const;
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static SourceRange genName(raw_ostream &os, const MemRegion *R,
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ASTContext &Ctx);
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static SmallVector<const MemRegion *, 4>
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getCapturedStackRegions(const BlockDataRegion &B, CheckerContext &C);
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static bool isArcManagedBlock(const MemRegion *R, CheckerContext &C);
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static bool isNotInCurrentFrame(const MemRegion *R, CheckerContext &C);
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};
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} // namespace
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SourceRange StackAddrEscapeChecker::genName(raw_ostream &os, const MemRegion *R,
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ASTContext &Ctx) {
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// Get the base region, stripping away fields and elements.
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R = R->getBaseRegion();
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SourceManager &SM = Ctx.getSourceManager();
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SourceRange range;
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os << "Address of ";
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// Check if the region is a compound literal.
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if (const auto *CR = dyn_cast<CompoundLiteralRegion>(R)) {
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const CompoundLiteralExpr *CL = CR->getLiteralExpr();
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os << "stack memory associated with a compound literal "
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"declared on line "
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<< SM.getExpansionLineNumber(CL->getBeginLoc()) << " returned to caller";
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range = CL->getSourceRange();
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} else if (const auto *AR = dyn_cast<AllocaRegion>(R)) {
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const Expr *ARE = AR->getExpr();
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SourceLocation L = ARE->getBeginLoc();
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range = ARE->getSourceRange();
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os << "stack memory allocated by call to alloca() on line "
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<< SM.getExpansionLineNumber(L);
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} else if (const auto *BR = dyn_cast<BlockDataRegion>(R)) {
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const BlockDecl *BD = BR->getCodeRegion()->getDecl();
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SourceLocation L = BD->getBeginLoc();
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range = BD->getSourceRange();
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os << "stack-allocated block declared on line "
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<< SM.getExpansionLineNumber(L);
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} else if (const auto *VR = dyn_cast<VarRegion>(R)) {
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os << "stack memory associated with local variable '" << VR->getString()
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<< '\'';
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range = VR->getDecl()->getSourceRange();
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} else if (const auto *TOR = dyn_cast<CXXTempObjectRegion>(R)) {
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QualType Ty = TOR->getValueType().getLocalUnqualifiedType();
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os << "stack memory associated with temporary object of type '";
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Ty.print(os, Ctx.getPrintingPolicy());
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os << "'";
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range = TOR->getExpr()->getSourceRange();
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} else {
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llvm_unreachable("Invalid region in ReturnStackAddressChecker.");
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}
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return range;
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}
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bool StackAddrEscapeChecker::isArcManagedBlock(const MemRegion *R,
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CheckerContext &C) {
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assert(R && "MemRegion should not be null");
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return C.getASTContext().getLangOpts().ObjCAutoRefCount &&
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isa<BlockDataRegion>(R);
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}
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bool StackAddrEscapeChecker::isNotInCurrentFrame(const MemRegion *R,
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CheckerContext &C) {
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const StackSpaceRegion *S = cast<StackSpaceRegion>(R->getMemorySpace());
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return S->getStackFrame() != C.getStackFrame();
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}
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bool StackAddrEscapeChecker::isSemaphoreCaptured(const BlockDecl &B) const {
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if (!dispatch_semaphore_tII)
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dispatch_semaphore_tII = &B.getASTContext().Idents.get("dispatch_semaphore_t");
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for (const auto &C : B.captures()) {
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const auto *T = C.getVariable()->getType()->getAs<TypedefType>();
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if (T && T->getDecl()->getIdentifier() == dispatch_semaphore_tII)
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return true;
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}
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return false;
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}
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SmallVector<const MemRegion *, 4>
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StackAddrEscapeChecker::getCapturedStackRegions(const BlockDataRegion &B,
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CheckerContext &C) {
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SmallVector<const MemRegion *, 4> Regions;
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BlockDataRegion::referenced_vars_iterator I = B.referenced_vars_begin();
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BlockDataRegion::referenced_vars_iterator E = B.referenced_vars_end();
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for (; I != E; ++I) {
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SVal Val = C.getState()->getSVal(I.getCapturedRegion());
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const MemRegion *Region = Val.getAsRegion();
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if (Region && isa<StackSpaceRegion>(Region->getMemorySpace()))
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Regions.push_back(Region);
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}
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return Regions;
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}
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void StackAddrEscapeChecker::EmitStackError(CheckerContext &C,
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const MemRegion *R,
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const Expr *RetE) const {
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ExplodedNode *N = C.generateNonFatalErrorNode();
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if (!N)
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return;
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if (!BT_returnstack)
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BT_returnstack = std::make_unique<BuiltinBug>(
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CheckNames[CK_StackAddrEscapeChecker],
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"Return of address to stack-allocated memory");
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// Generate a report for this bug.
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SmallString<128> buf;
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llvm::raw_svector_ostream os(buf);
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SourceRange range = genName(os, R, C.getASTContext());
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os << " returned to caller";
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auto report =
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std::make_unique<PathSensitiveBugReport>(*BT_returnstack, os.str(), N);
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report->addRange(RetE->getSourceRange());
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if (range.isValid())
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report->addRange(range);
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C.emitReport(std::move(report));
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}
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void StackAddrEscapeChecker::checkAsyncExecutedBlockCaptures(
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const BlockDataRegion &B, CheckerContext &C) const {
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// There is a not-too-uncommon idiom
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// where a block passed to dispatch_async captures a semaphore
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// and then the thread (which called dispatch_async) is blocked on waiting
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// for the completion of the execution of the block
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// via dispatch_semaphore_wait. To avoid false-positives (for now)
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// we ignore all the blocks which have captured
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// a variable of the type "dispatch_semaphore_t".
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if (isSemaphoreCaptured(*B.getDecl()))
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return;
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for (const MemRegion *Region : getCapturedStackRegions(B, C)) {
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// The block passed to dispatch_async may capture another block
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// created on the stack. However, there is no leak in this situaton,
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// no matter if ARC or no ARC is enabled:
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// dispatch_async copies the passed "outer" block (via Block_copy)
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// and if the block has captured another "inner" block,
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// the "inner" block will be copied as well.
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if (isa<BlockDataRegion>(Region))
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continue;
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ExplodedNode *N = C.generateNonFatalErrorNode();
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if (!N)
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continue;
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if (!BT_capturedstackasync)
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BT_capturedstackasync = std::make_unique<BuiltinBug>(
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CheckNames[CK_StackAddrAsyncEscapeChecker],
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"Address of stack-allocated memory is captured");
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SmallString<128> Buf;
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llvm::raw_svector_ostream Out(Buf);
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SourceRange Range = genName(Out, Region, C.getASTContext());
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Out << " is captured by an asynchronously-executed block";
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auto Report = std::make_unique<PathSensitiveBugReport>(
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*BT_capturedstackasync, Out.str(), N);
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if (Range.isValid())
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Report->addRange(Range);
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C.emitReport(std::move(Report));
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}
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}
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void StackAddrEscapeChecker::checkReturnedBlockCaptures(
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const BlockDataRegion &B, CheckerContext &C) const {
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for (const MemRegion *Region : getCapturedStackRegions(B, C)) {
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if (isArcManagedBlock(Region, C) || isNotInCurrentFrame(Region, C))
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continue;
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ExplodedNode *N = C.generateNonFatalErrorNode();
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if (!N)
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continue;
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if (!BT_capturedstackret)
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BT_capturedstackret = std::make_unique<BuiltinBug>(
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CheckNames[CK_StackAddrEscapeChecker],
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"Address of stack-allocated memory is captured");
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SmallString<128> Buf;
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llvm::raw_svector_ostream Out(Buf);
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SourceRange Range = genName(Out, Region, C.getASTContext());
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Out << " is captured by a returned block";
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auto Report = std::make_unique<PathSensitiveBugReport>(*BT_capturedstackret,
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Out.str(), N);
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if (Range.isValid())
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Report->addRange(Range);
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C.emitReport(std::move(Report));
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}
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}
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void StackAddrEscapeChecker::checkPreCall(const CallEvent &Call,
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CheckerContext &C) const {
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if (!ChecksEnabled[CK_StackAddrAsyncEscapeChecker])
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return;
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if (!Call.isGlobalCFunction("dispatch_after") &&
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!Call.isGlobalCFunction("dispatch_async"))
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return;
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for (unsigned Idx = 0, NumArgs = Call.getNumArgs(); Idx < NumArgs; ++Idx) {
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if (const BlockDataRegion *B = dyn_cast_or_null<BlockDataRegion>(
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Call.getArgSVal(Idx).getAsRegion()))
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checkAsyncExecutedBlockCaptures(*B, C);
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}
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}
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void StackAddrEscapeChecker::checkPreStmt(const ReturnStmt *RS,
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CheckerContext &C) const {
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if (!ChecksEnabled[CK_StackAddrEscapeChecker])
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return;
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const Expr *RetE = RS->getRetValue();
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if (!RetE)
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return;
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RetE = RetE->IgnoreParens();
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SVal V = C.getSVal(RetE);
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const MemRegion *R = V.getAsRegion();
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if (!R)
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return;
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if (const BlockDataRegion *B = dyn_cast<BlockDataRegion>(R))
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checkReturnedBlockCaptures(*B, C);
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if (!isa<StackSpaceRegion>(R->getMemorySpace()) ||
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isNotInCurrentFrame(R, C) || isArcManagedBlock(R, C))
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return;
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// Returning a record by value is fine. (In this case, the returned
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// expression will be a copy-constructor, possibly wrapped in an
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// ExprWithCleanups node.)
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if (const ExprWithCleanups *Cleanup = dyn_cast<ExprWithCleanups>(RetE))
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RetE = Cleanup->getSubExpr();
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if (isa<CXXConstructExpr>(RetE) && RetE->getType()->isRecordType())
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return;
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// The CK_CopyAndAutoreleaseBlockObject cast causes the block to be copied
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// so the stack address is not escaping here.
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if (const auto *ICE = dyn_cast<ImplicitCastExpr>(RetE)) {
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if (isa<BlockDataRegion>(R) &&
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ICE->getCastKind() == CK_CopyAndAutoreleaseBlockObject) {
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return;
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}
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}
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EmitStackError(C, R, RetE);
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}
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void StackAddrEscapeChecker::checkEndFunction(const ReturnStmt *RS,
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CheckerContext &Ctx) const {
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if (!ChecksEnabled[CK_StackAddrEscapeChecker])
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return;
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ProgramStateRef State = Ctx.getState();
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// Iterate over all bindings to global variables and see if it contains
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// a memory region in the stack space.
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class CallBack : public StoreManager::BindingsHandler {
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private:
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CheckerContext &Ctx;
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const StackFrameContext *CurSFC;
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public:
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SmallVector<std::pair<const MemRegion *, const MemRegion *>, 10> V;
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CallBack(CheckerContext &CC) : Ctx(CC), CurSFC(CC.getStackFrame()) {}
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bool HandleBinding(StoreManager &SMgr, Store S, const MemRegion *Region,
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SVal Val) override {
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if (!isa<GlobalsSpaceRegion>(Region->getMemorySpace()))
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return true;
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const MemRegion *VR = Val.getAsRegion();
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if (VR && isa<StackSpaceRegion>(VR->getMemorySpace()) &&
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!isArcManagedBlock(VR, Ctx) && !isNotInCurrentFrame(VR, Ctx))
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V.emplace_back(Region, VR);
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return true;
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}
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};
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CallBack Cb(Ctx);
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State->getStateManager().getStoreManager().iterBindings(State->getStore(),
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Cb);
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if (Cb.V.empty())
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return;
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// Generate an error node.
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ExplodedNode *N = Ctx.generateNonFatalErrorNode(State);
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if (!N)
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return;
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if (!BT_stackleak)
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BT_stackleak = std::make_unique<BuiltinBug>(
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CheckNames[CK_StackAddrEscapeChecker],
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"Stack address stored into global variable",
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"Stack address was saved into a global variable. "
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"This is dangerous because the address will become "
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"invalid after returning from the function");
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for (const auto &P : Cb.V) {
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// Generate a report for this bug.
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SmallString<128> Buf;
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llvm::raw_svector_ostream Out(Buf);
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SourceRange Range = genName(Out, P.second, Ctx.getASTContext());
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Out << " is still referred to by the ";
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if (isa<StaticGlobalSpaceRegion>(P.first->getMemorySpace()))
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Out << "static";
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else
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Out << "global";
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Out << " variable '";
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const VarRegion *VR = cast<VarRegion>(P.first->getBaseRegion());
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Out << *VR->getDecl()
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<< "' upon returning to the caller. This will be a dangling reference";
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auto Report =
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std::make_unique<PathSensitiveBugReport>(*BT_stackleak, Out.str(), N);
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if (Range.isValid())
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Report->addRange(Range);
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Ctx.emitReport(std::move(Report));
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}
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}
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void ento::registerStackAddrEscapeBase(CheckerManager &mgr) {
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mgr.registerChecker<StackAddrEscapeChecker>();
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}
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bool ento::shouldRegisterStackAddrEscapeBase(const CheckerManager &mgr) {
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return true;
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}
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#define REGISTER_CHECKER(name) \
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void ento::register##name(CheckerManager &Mgr) { \
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StackAddrEscapeChecker *Chk = Mgr.getChecker<StackAddrEscapeChecker>(); \
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Chk->ChecksEnabled[StackAddrEscapeChecker::CK_##name] = true; \
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Chk->CheckNames[StackAddrEscapeChecker::CK_##name] = \
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Mgr.getCurrentCheckerName(); \
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} \
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\
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bool ento::shouldRegister##name(const CheckerManager &mgr) { return true; }
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REGISTER_CHECKER(StackAddrEscapeChecker)
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REGISTER_CHECKER(StackAddrAsyncEscapeChecker)
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