244 lines
8.3 KiB
C++
244 lines
8.3 KiB
C++
//=== StackAddrEscapeChecker.cpp ----------------------------------*- C++ -*--//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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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 "ClangSACheckers.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/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 : public Checker< check::PreStmt<ReturnStmt>,
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check::EndFunction > {
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mutable OwningPtr<BuiltinBug> BT_stackleak;
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mutable OwningPtr<BuiltinBug> BT_returnstack;
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public:
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void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const;
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void checkEndFunction(CheckerContext &Ctx) const;
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private:
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void EmitStackError(CheckerContext &C, const MemRegion *R,
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const Expr *RetE) const;
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static SourceRange genName(raw_ostream &os, const MemRegion *R,
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ASTContext &Ctx);
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};
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}
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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 CompoundLiteralRegion* 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->getLocStart())
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<< " returned to caller";
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range = CL->getSourceRange();
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}
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else if (const AllocaRegion* AR = dyn_cast<AllocaRegion>(R)) {
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const Expr *ARE = AR->getExpr();
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SourceLocation L = ARE->getLocStart();
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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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}
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else if (const BlockDataRegion *BR = dyn_cast<BlockDataRegion>(R)) {
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const BlockDecl *BD = BR->getCodeRegion()->getDecl();
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SourceLocation L = BD->getLocStart();
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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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}
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else if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
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os << "stack memory associated with local variable '"
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<< VR->getString() << '\'';
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range = VR->getDecl()->getSourceRange();
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}
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else if (const CXXTempObjectRegion *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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}
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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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void StackAddrEscapeChecker::EmitStackError(CheckerContext &C, const MemRegion *R,
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const Expr *RetE) const {
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ExplodedNode *N = C.generateSink();
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if (!N)
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return;
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if (!BT_returnstack)
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BT_returnstack.reset(
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new BuiltinBug("Return of address to stack-allocated memory"));
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// Generate a report for this bug.
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SmallString<512> 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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BugReport *report = new BugReport(*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(report);
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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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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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const LocationContext *LCtx = C.getLocationContext();
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SVal V = C.getState()->getSVal(RetE, LCtx);
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const MemRegion *R = V.getAsRegion();
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if (!R)
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return;
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const StackSpaceRegion *SS =
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dyn_cast_or_null<StackSpaceRegion>(R->getMemorySpace());
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if (!SS)
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return;
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// Return stack memory in an ancestor stack frame is fine.
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const StackFrameContext *CurFrame = LCtx->getCurrentStackFrame();
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const StackFrameContext *MemFrame = SS->getStackFrame();
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if (MemFrame != CurFrame)
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return;
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// Automatic reference counting automatically copies blocks.
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if (C.getASTContext().getLangOpts().ObjCAutoRefCount &&
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isa<BlockDataRegion>(R))
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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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EmitStackError(C, R, RetE);
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}
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void StackAddrEscapeChecker::checkEndFunction(CheckerContext &Ctx) const {
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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) :
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Ctx(CC),
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CurSFC(CC.getLocationContext()->getCurrentStackFrame())
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{}
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bool HandleBinding(StoreManager &SMgr, Store store,
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const MemRegion *region, SVal val) {
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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)
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return true;
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// Under automated retain release, it is okay to assign a block
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// directly to a global variable.
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if (Ctx.getASTContext().getLangOpts().ObjCAutoRefCount &&
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isa<BlockDataRegion>(vR))
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return true;
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if (const StackSpaceRegion *SSR =
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dyn_cast<StackSpaceRegion>(vR->getMemorySpace())) {
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// If the global variable holds a location in the current stack frame,
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// record the binding to emit a warning.
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if (SSR->getStackFrame() == CurSFC)
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V.push_back(std::make_pair(region, vR));
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}
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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(),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.addTransition(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.reset(
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new BuiltinBug("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 (unsigned i = 0, e = cb.V.size(); i != e; ++i) {
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// Generate a report for this bug.
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SmallString<512> buf;
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llvm::raw_svector_ostream os(buf);
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SourceRange range = genName(os, cb.V[i].second, Ctx.getASTContext());
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os << " is still referred to by the global variable '";
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const VarRegion *VR = cast<VarRegion>(cb.V[i].first->getBaseRegion());
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os << *VR->getDecl()
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<< "' upon returning to the caller. This will be a dangling reference";
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BugReport *report = new BugReport(*BT_stackleak, os.str(), N);
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if (range.isValid())
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report->addRange(range);
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Ctx.emitReport(report);
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}
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}
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void ento::registerStackAddrEscapeChecker(CheckerManager &mgr) {
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mgr.registerChecker<StackAddrEscapeChecker>();
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}
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