1 //=== StackAddrEscapeChecker.cpp ----------------------------------*- C++ -*--// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file defines stack address leak checker, which checks if an invalid 11 // stack address is stored into a global or heap location. See CERT DCL30-C. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "ClangSACheckers.h" 16 #include "clang/StaticAnalyzer/Core/Checker.h" 17 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 19 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 20 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" 21 #include "clang/Basic/SourceManager.h" 22 #include "llvm/ADT/SmallString.h" 23 using namespace clang; 24 using namespace ento; 25 26 namespace { 27 class StackAddrEscapeChecker : public Checker< check::PreStmt<ReturnStmt>, 28 check::EndPath > { 29 mutable llvm::OwningPtr<BuiltinBug> BT_stackleak; 30 mutable llvm::OwningPtr<BuiltinBug> BT_returnstack; 31 32 public: 33 void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const; 34 void checkEndPath(EndOfFunctionNodeBuilder &B, ExprEngine &Eng) const; 35 private: 36 void EmitStackError(CheckerContext &C, const MemRegion *R, 37 const Expr *RetE) const; 38 static SourceRange GenName(raw_ostream &os, const MemRegion *R, 39 SourceManager &SM); 40 }; 41 } 42 43 SourceRange StackAddrEscapeChecker::GenName(raw_ostream &os, 44 const MemRegion *R, 45 SourceManager &SM) { 46 // Get the base region, stripping away fields and elements. 47 R = R->getBaseRegion(); 48 SourceRange range; 49 os << "Address of "; 50 51 // Check if the region is a compound literal. 52 if (const CompoundLiteralRegion* CR = dyn_cast<CompoundLiteralRegion>(R)) { 53 const CompoundLiteralExpr *CL = CR->getLiteralExpr(); 54 os << "stack memory associated with a compound literal " 55 "declared on line " 56 << SM.getExpansionLineNumber(CL->getLocStart()) 57 << " returned to caller"; 58 range = CL->getSourceRange(); 59 } 60 else if (const AllocaRegion* AR = dyn_cast<AllocaRegion>(R)) { 61 const Expr *ARE = AR->getExpr(); 62 SourceLocation L = ARE->getLocStart(); 63 range = ARE->getSourceRange(); 64 os << "stack memory allocated by call to alloca() on line " 65 << SM.getExpansionLineNumber(L); 66 } 67 else if (const BlockDataRegion *BR = dyn_cast<BlockDataRegion>(R)) { 68 const BlockDecl *BD = BR->getCodeRegion()->getDecl(); 69 SourceLocation L = BD->getLocStart(); 70 range = BD->getSourceRange(); 71 os << "stack-allocated block declared on line " 72 << SM.getExpansionLineNumber(L); 73 } 74 else if (const VarRegion *VR = dyn_cast<VarRegion>(R)) { 75 os << "stack memory associated with local variable '" 76 << VR->getString() << '\''; 77 range = VR->getDecl()->getSourceRange(); 78 } 79 else if (const CXXTempObjectRegion *TOR = dyn_cast<CXXTempObjectRegion>(R)) { 80 os << "stack memory associated with temporary object of type '" 81 << TOR->getValueType().getAsString() << '\''; 82 range = TOR->getExpr()->getSourceRange(); 83 } 84 else { 85 llvm_unreachable("Invalid region in ReturnStackAddressChecker."); 86 } 87 88 return range; 89 } 90 91 void StackAddrEscapeChecker::EmitStackError(CheckerContext &C, const MemRegion *R, 92 const Expr *RetE) const { 93 ExplodedNode *N = C.generateSink(); 94 95 if (!N) 96 return; 97 98 if (!BT_returnstack) 99 BT_returnstack.reset( 100 new BuiltinBug("Return of address to stack-allocated memory")); 101 102 // Generate a report for this bug. 103 llvm::SmallString<512> buf; 104 llvm::raw_svector_ostream os(buf); 105 SourceRange range = GenName(os, R, C.getSourceManager()); 106 os << " returned to caller"; 107 BugReport *report = new BugReport(*BT_returnstack, os.str(), N); 108 report->addRange(RetE->getSourceRange()); 109 if (range.isValid()) 110 report->addRange(range); 111 112 C.EmitReport(report); 113 } 114 115 void StackAddrEscapeChecker::checkPreStmt(const ReturnStmt *RS, 116 CheckerContext &C) const { 117 118 const Expr *RetE = RS->getRetValue(); 119 if (!RetE) 120 return; 121 122 SVal V = C.getState()->getSVal(RetE); 123 const MemRegion *R = V.getAsRegion(); 124 125 if (!R || !R->hasStackStorage()) 126 return; 127 128 if (R->hasStackStorage()) { 129 // Automatic reference counting automatically copies blocks. 130 if (C.getASTContext().getLangOptions().ObjCAutoRefCount && 131 isa<BlockDataRegion>(R)) 132 return; 133 134 EmitStackError(C, R, RetE); 135 return; 136 } 137 } 138 139 void StackAddrEscapeChecker::checkEndPath(EndOfFunctionNodeBuilder &B, 140 ExprEngine &Eng) const { 141 142 const ProgramState *state = B.getState(); 143 144 // Iterate over all bindings to global variables and see if it contains 145 // a memory region in the stack space. 146 class CallBack : public StoreManager::BindingsHandler { 147 private: 148 ExprEngine &Eng; 149 const StackFrameContext *CurSFC; 150 public: 151 SmallVector<std::pair<const MemRegion*, const MemRegion*>, 10> V; 152 153 CallBack(ExprEngine &Eng, const LocationContext *LCtx) 154 : Eng(Eng), CurSFC(LCtx->getCurrentStackFrame()) {} 155 156 bool HandleBinding(StoreManager &SMgr, Store store, 157 const MemRegion *region, SVal val) { 158 159 if (!isa<GlobalsSpaceRegion>(region->getMemorySpace())) 160 return true; 161 162 const MemRegion *vR = val.getAsRegion(); 163 if (!vR) 164 return true; 165 166 // Under automated retain release, it is okay to assign a block 167 // directly to a global variable. 168 if (Eng.getContext().getLangOptions().ObjCAutoRefCount && 169 isa<BlockDataRegion>(vR)) 170 return true; 171 172 if (const StackSpaceRegion *SSR = 173 dyn_cast<StackSpaceRegion>(vR->getMemorySpace())) { 174 // If the global variable holds a location in the current stack frame, 175 // record the binding to emit a warning. 176 if (SSR->getStackFrame() == CurSFC) 177 V.push_back(std::make_pair(region, vR)); 178 } 179 180 return true; 181 } 182 }; 183 184 CallBack cb(Eng, B.getPredecessor()->getLocationContext()); 185 state->getStateManager().getStoreManager().iterBindings(state->getStore(),cb); 186 187 if (cb.V.empty()) 188 return; 189 190 // Generate an error node. 191 ExplodedNode *N = B.generateNode(state); 192 if (!N) 193 return; 194 195 if (!BT_stackleak) 196 BT_stackleak.reset( 197 new BuiltinBug("Stack address stored into global variable", 198 "Stack address was saved into a global variable. " 199 "This is dangerous because the address will become " 200 "invalid after returning from the function")); 201 202 for (unsigned i = 0, e = cb.V.size(); i != e; ++i) { 203 // Generate a report for this bug. 204 llvm::SmallString<512> buf; 205 llvm::raw_svector_ostream os(buf); 206 SourceRange range = GenName(os, cb.V[i].second, 207 Eng.getContext().getSourceManager()); 208 os << " is still referred to by the global variable '"; 209 const VarRegion *VR = cast<VarRegion>(cb.V[i].first->getBaseRegion()); 210 os << *VR->getDecl() 211 << "' upon returning to the caller. This will be a dangling reference"; 212 BugReport *report = new BugReport(*BT_stackleak, os.str(), N); 213 if (range.isValid()) 214 report->addRange(range); 215 216 Eng.getBugReporter().EmitReport(report); 217 } 218 } 219 220 void ento::registerStackAddrEscapeChecker(CheckerManager &mgr) { 221 mgr.registerChecker<StackAddrEscapeChecker>(); 222 } 223