StackAddrEscapeChecker.cpp revision c210cb7a358d14cdd93b58562f33ff5ed2d895c1
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" 23using namespace clang; 24using namespace ento; 25 26namespace { 27class StackAddrEscapeChecker : public Checker< check::PreStmt<ReturnStmt>, 28 check::EndPath > { 29 mutable OwningPtr<BuiltinBug> BT_stackleak; 30 mutable OwningPtr<BuiltinBug> BT_returnstack; 31 32public: 33 void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const; 34 void checkEndPath(CheckerContext &Ctx) const; 35private: 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 43SourceRange 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 91void 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 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 115void StackAddrEscapeChecker::checkPreStmt(const ReturnStmt *RS, 116 CheckerContext &C) const { 117 118 const Expr *RetE = RS->getRetValue(); 119 if (!RetE) 120 return; 121 122 const LocationContext *LCtx = C.getLocationContext(); 123 SVal V = C.getState()->getSVal(RetE, LCtx); 124 const MemRegion *R = V.getAsRegion(); 125 126 if (!R) 127 return; 128 129 const StackSpaceRegion *SS = 130 dyn_cast_or_null<StackSpaceRegion>(R->getMemorySpace()); 131 132 if (!SS) 133 return; 134 135 // Return stack memory in an ancestor stack frame is fine. 136 const StackFrameContext *CurFrame = LCtx->getCurrentStackFrame(); 137 const StackFrameContext *MemFrame = SS->getStackFrame(); 138 if (MemFrame != CurFrame) 139 return; 140 141 // Automatic reference counting automatically copies blocks. 142 if (C.getASTContext().getLangOpts().ObjCAutoRefCount && 143 isa<BlockDataRegion>(R)) 144 return; 145 146 // Returning a record by value is fine. (In this case, the returned 147 // expression will be a copy-constructor.) 148 if (isa<CXXConstructExpr>(RetE) && RetE->getType()->isRecordType()) 149 return; 150 151 EmitStackError(C, R, RetE); 152} 153 154void StackAddrEscapeChecker::checkEndPath(CheckerContext &Ctx) const { 155 ProgramStateRef state = Ctx.getState(); 156 157 // Iterate over all bindings to global variables and see if it contains 158 // a memory region in the stack space. 159 class CallBack : public StoreManager::BindingsHandler { 160 private: 161 CheckerContext &Ctx; 162 const StackFrameContext *CurSFC; 163 public: 164 SmallVector<std::pair<const MemRegion*, const MemRegion*>, 10> V; 165 166 CallBack(CheckerContext &CC) : 167 Ctx(CC), 168 CurSFC(CC.getLocationContext()->getCurrentStackFrame()) 169 {} 170 171 bool HandleBinding(StoreManager &SMgr, Store store, 172 const MemRegion *region, SVal val) { 173 174 if (!isa<GlobalsSpaceRegion>(region->getMemorySpace())) 175 return true; 176 177 const MemRegion *vR = val.getAsRegion(); 178 if (!vR) 179 return true; 180 181 // Under automated retain release, it is okay to assign a block 182 // directly to a global variable. 183 if (Ctx.getASTContext().getLangOpts().ObjCAutoRefCount && 184 isa<BlockDataRegion>(vR)) 185 return true; 186 187 if (const StackSpaceRegion *SSR = 188 dyn_cast<StackSpaceRegion>(vR->getMemorySpace())) { 189 // If the global variable holds a location in the current stack frame, 190 // record the binding to emit a warning. 191 if (SSR->getStackFrame() == CurSFC) 192 V.push_back(std::make_pair(region, vR)); 193 } 194 195 return true; 196 } 197 }; 198 199 CallBack cb(Ctx); 200 state->getStateManager().getStoreManager().iterBindings(state->getStore(),cb); 201 202 if (cb.V.empty()) 203 return; 204 205 // Generate an error node. 206 ExplodedNode *N = Ctx.addTransition(state); 207 if (!N) 208 return; 209 210 if (!BT_stackleak) 211 BT_stackleak.reset( 212 new BuiltinBug("Stack address stored into global variable", 213 "Stack address was saved into a global variable. " 214 "This is dangerous because the address will become " 215 "invalid after returning from the function")); 216 217 for (unsigned i = 0, e = cb.V.size(); i != e; ++i) { 218 // Generate a report for this bug. 219 SmallString<512> buf; 220 llvm::raw_svector_ostream os(buf); 221 SourceRange range = GenName(os, cb.V[i].second, 222 Ctx.getSourceManager()); 223 os << " is still referred to by the global variable '"; 224 const VarRegion *VR = cast<VarRegion>(cb.V[i].first->getBaseRegion()); 225 os << *VR->getDecl() 226 << "' upon returning to the caller. This will be a dangling reference"; 227 BugReport *report = new BugReport(*BT_stackleak, os.str(), N); 228 if (range.isValid()) 229 report->addRange(range); 230 231 Ctx.EmitReport(report); 232 } 233} 234 235void ento::registerStackAddrEscapeChecker(CheckerManager &mgr) { 236 mgr.registerChecker<StackAddrEscapeChecker>(); 237} 238