684c26c89b
This patch simplifies the diagnostic message in the core.StackAddrEscape for stack memory associated with compound literals by removing the redundant "returned to caller" suffix. Example: https://godbolt.org/z/KxM67vr7c ```c // clang --analyze -Xanalyzer -analyzer-checker=core.StackAddressEscape void* compound_literal() { return &(unsigned short){((unsigned short)0x22EF)}; } ``` warning: Address of stack memory associated with a compound literal declared on line 2 **returned to caller returned to caller** [core.StackAddressEscape]
555 lines
21 KiB
C++
555 lines
21 KiB
C++
//=== 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/AST/ExprCXX.h"
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#include "clang/Basic/SourceManager.h"
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#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.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 = nullptr;
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mutable std::unique_ptr<BugType> BT_stackleak;
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mutable std::unique_ptr<BugType> BT_returnstack;
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mutable std::unique_ptr<BugType> BT_capturedstackasync;
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mutable std::unique_ptr<BugType> 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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bool ChecksEnabled[CK_NumCheckKinds] = {false};
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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 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());
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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 *LER = dyn_cast<CXXLifetimeExtendedObjectRegion>(R)) {
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QualType Ty = LER->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 << "' lifetime extended by local variable";
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if (const IdentifierInfo *ID = LER->getExtendingDecl()->getIdentifier())
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os << " '" << ID->getName() << '\'';
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range = LER->getExpr()->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::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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for (auto Var : B.referenced_vars()) {
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SVal Val = C.getState()->getSVal(Var.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<BugType>(
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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<BugType>(
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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 (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<BugType>(
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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()) || isNotInCurrentFrame(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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static const MemSpaceRegion *getStackOrGlobalSpaceRegion(const MemRegion *R) {
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assert(R);
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if (const auto *MemSpace = R->getMemorySpace()) {
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if (const auto *SSR = MemSpace->getAs<StackSpaceRegion>())
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return SSR;
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if (const auto *GSR = MemSpace->getAs<GlobalsSpaceRegion>())
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return GSR;
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}
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// If R describes a lambda capture, it will be a symbolic region
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// referring to a field region of another symbolic region.
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if (const auto *SymReg = R->getBaseRegion()->getAs<SymbolicRegion>()) {
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if (const auto *OriginReg = SymReg->getSymbol()->getOriginRegion())
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return getStackOrGlobalSpaceRegion(OriginReg);
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}
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return nullptr;
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}
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static const MemRegion *getOriginBaseRegion(const MemRegion *Reg) {
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Reg = Reg->getBaseRegion();
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while (const auto *SymReg = dyn_cast<SymbolicRegion>(Reg)) {
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const auto *OriginReg = SymReg->getSymbol()->getOriginRegion();
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if (!OriginReg)
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break;
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Reg = OriginReg->getBaseRegion();
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}
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return Reg;
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}
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static std::optional<std::string> printReferrer(const MemRegion *Referrer) {
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assert(Referrer);
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const StringRef ReferrerMemorySpace = [](const MemSpaceRegion *Space) {
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if (isa<StaticGlobalSpaceRegion>(Space))
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return "static";
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if (isa<GlobalsSpaceRegion>(Space))
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return "global";
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assert(isa<StackSpaceRegion>(Space));
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// This case covers top-level and inlined analyses.
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return "caller";
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}(getStackOrGlobalSpaceRegion(Referrer));
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while (!Referrer->canPrintPretty()) {
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if (const auto *SymReg = dyn_cast<SymbolicRegion>(Referrer);
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SymReg && SymReg->getSymbol()->getOriginRegion()) {
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Referrer = SymReg->getSymbol()->getOriginRegion()->getBaseRegion();
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} else if (isa<CXXThisRegion>(Referrer)) {
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// Skip members of a class, it is handled in CheckExprLifetime.cpp as
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// warn_bind_ref_member_to_parameter or
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// warn_init_ptr_member_to_parameter_addr
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return std::nullopt;
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} else if (isa<AllocaRegion>(Referrer)) {
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// Skip alloca() regions, they indicate advanced memory management
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// and higher likelihood of CSA false positives.
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return std::nullopt;
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} else {
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assert(false && "Unexpected referrer region type.");
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return std::nullopt;
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}
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}
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assert(Referrer);
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assert(Referrer->canPrintPretty());
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std::string buf;
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llvm::raw_string_ostream os(buf);
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os << ReferrerMemorySpace << " variable ";
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Referrer->printPretty(os);
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return buf;
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}
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/// Check whether \p Region refers to a freshly minted symbol after an opaque
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/// function call.
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static bool isInvalidatedSymbolRegion(const MemRegion *Region) {
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const auto *SymReg = Region->getAs<SymbolicRegion>();
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if (!SymReg)
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return false;
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SymbolRef Symbol = SymReg->getSymbol();
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const auto *DerS = dyn_cast<SymbolDerived>(Symbol);
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return DerS && isa_and_nonnull<SymbolConjured>(DerS->getParentSymbol());
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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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ExplodedNode *Node = Ctx.getPredecessor();
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bool ExitingTopFrame =
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Ctx.getPredecessor()->getLocationContext()->inTopFrame();
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if (ExitingTopFrame &&
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Node->getLocation().getTag() == ExprEngine::cleanupNodeTag() &&
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Node->getFirstPred()) {
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// When finishing analysis of a top-level function, engine proactively
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// removes dead symbols thus preventing this checker from looking through
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// the output parameters. Take 1 step back, to the node where these symbols
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// and their bindings are still present
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Node = Node->getFirstPred();
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}
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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 *PoppedFrame;
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const bool TopFrame;
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/// Look for stack variables referring to popped stack variables.
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/// Returns true only if it found some dangling stack variables
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/// referred by an other stack variable from different stack frame.
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bool checkForDanglingStackVariable(const MemRegion *Referrer,
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const MemRegion *Referred) {
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const auto *ReferrerMemSpace = getStackOrGlobalSpaceRegion(Referrer);
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const auto *ReferredMemSpace =
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Referred->getMemorySpace()->getAs<StackSpaceRegion>();
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if (!ReferrerMemSpace || !ReferredMemSpace)
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return false;
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const auto *ReferrerStackSpace =
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ReferrerMemSpace->getAs<StackSpaceRegion>();
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if (!ReferrerStackSpace)
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return false;
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if (const auto *ReferredFrame = ReferredMemSpace->getStackFrame();
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ReferredFrame != PoppedFrame) {
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return false;
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}
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if (ReferrerStackSpace->getStackFrame()->isParentOf(PoppedFrame)) {
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V.emplace_back(Referrer, Referred);
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return true;
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}
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if (isa<StackArgumentsSpaceRegion>(ReferrerMemSpace) &&
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// Not a simple ptr (int*) but something deeper, e.g. int**
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isa<SymbolicRegion>(Referrer->getBaseRegion()) &&
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ReferrerStackSpace->getStackFrame() == PoppedFrame && TopFrame) {
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// Output parameter of a top-level function
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V.emplace_back(Referrer, Referred);
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return true;
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}
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return false;
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}
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// Keep track of the variables that were invalidated through an opaque
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// function call. Even if the initial values of such variables were bound to
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// an address of a local variable, we cannot claim anything now, at the
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// function exit, so skip them to avoid false positives.
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void recordInInvalidatedRegions(const MemRegion *Region) {
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if (isInvalidatedSymbolRegion(Region))
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ExcludedRegions.insert(getOriginBaseRegion(Region));
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}
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public:
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SmallVector<std::pair<const MemRegion *, const MemRegion *>, 10> V;
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// ExcludedRegions are skipped from reporting.
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// I.e., if a referrer in this set, skip the related bug report.
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// It is useful to avoid false positive for the variables that were
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// reset to a conjured value after an opaque function call.
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llvm::SmallPtrSet<const MemRegion *, 4> ExcludedRegions;
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|
|
|
CallBack(CheckerContext &CC, bool TopFrame)
|
|
: Ctx(CC), PoppedFrame(CC.getStackFrame()), TopFrame(TopFrame) {}
|
|
|
|
bool HandleBinding(StoreManager &SMgr, Store S, const MemRegion *Region,
|
|
SVal Val) override {
|
|
recordInInvalidatedRegions(Region);
|
|
const MemRegion *VR = Val.getAsRegion();
|
|
if (!VR)
|
|
return true;
|
|
|
|
if (checkForDanglingStackVariable(Region, VR))
|
|
return true;
|
|
|
|
// Check the globals for the same.
|
|
if (!isa_and_nonnull<GlobalsSpaceRegion>(
|
|
getStackOrGlobalSpaceRegion(Region)))
|
|
return true;
|
|
if (VR && VR->hasStackStorage() && !isNotInCurrentFrame(VR, Ctx))
|
|
V.emplace_back(Region, VR);
|
|
return true;
|
|
}
|
|
};
|
|
|
|
CallBack Cb(Ctx, ExitingTopFrame);
|
|
ProgramStateRef State = Node->getState();
|
|
State->getStateManager().getStoreManager().iterBindings(State->getStore(),
|
|
Cb);
|
|
|
|
if (Cb.V.empty())
|
|
return;
|
|
|
|
// Generate an error node.
|
|
ExplodedNode *N = Ctx.generateNonFatalErrorNode(State, Node);
|
|
if (!N)
|
|
return;
|
|
|
|
if (!BT_stackleak)
|
|
BT_stackleak =
|
|
std::make_unique<BugType>(CheckNames[CK_StackAddrEscapeChecker],
|
|
"Stack address leaks outside of stack frame");
|
|
|
|
for (const auto &P : Cb.V) {
|
|
const MemRegion *Referrer = P.first->getBaseRegion();
|
|
const MemRegion *Referred = P.second;
|
|
if (Cb.ExcludedRegions.contains(getOriginBaseRegion(Referrer))) {
|
|
continue;
|
|
}
|
|
|
|
// Generate a report for this bug.
|
|
const StringRef CommonSuffix =
|
|
" upon returning to the caller. This will be a dangling reference";
|
|
SmallString<128> Buf;
|
|
llvm::raw_svector_ostream Out(Buf);
|
|
const SourceRange Range = genName(Out, Referred, Ctx.getASTContext());
|
|
|
|
if (isa<CXXTempObjectRegion, CXXLifetimeExtendedObjectRegion>(Referrer)) {
|
|
Out << " is still referred to by a temporary object on the stack"
|
|
<< CommonSuffix;
|
|
auto Report =
|
|
std::make_unique<PathSensitiveBugReport>(*BT_stackleak, Out.str(), N);
|
|
if (Range.isValid())
|
|
Report->addRange(Range);
|
|
Ctx.emitReport(std::move(Report));
|
|
return;
|
|
}
|
|
|
|
auto ReferrerVariable = printReferrer(Referrer);
|
|
if (!ReferrerVariable) {
|
|
continue;
|
|
}
|
|
|
|
Out << " is still referred to by the " << *ReferrerVariable << CommonSuffix;
|
|
auto Report =
|
|
std::make_unique<PathSensitiveBugReport>(*BT_stackleak, Out.str(), N);
|
|
if (Range.isValid())
|
|
Report->addRange(Range);
|
|
|
|
Ctx.emitReport(std::move(Report));
|
|
}
|
|
}
|
|
|
|
void ento::registerStackAddrEscapeBase(CheckerManager &mgr) {
|
|
mgr.registerChecker<StackAddrEscapeChecker>();
|
|
}
|
|
|
|
bool ento::shouldRegisterStackAddrEscapeBase(const CheckerManager &mgr) {
|
|
return true;
|
|
}
|
|
|
|
#define REGISTER_CHECKER(name) \
|
|
void ento::register##name(CheckerManager &Mgr) { \
|
|
StackAddrEscapeChecker *Chk = Mgr.getChecker<StackAddrEscapeChecker>(); \
|
|
Chk->ChecksEnabled[StackAddrEscapeChecker::CK_##name] = true; \
|
|
Chk->CheckNames[StackAddrEscapeChecker::CK_##name] = \
|
|
Mgr.getCurrentCheckerName(); \
|
|
} \
|
|
\
|
|
bool ento::shouldRegister##name(const CheckerManager &mgr) { return true; }
|
|
|
|
REGISTER_CHECKER(StackAddrEscapeChecker)
|
|
REGISTER_CHECKER(StackAddrAsyncEscapeChecker)
|