StackAddrEscapeChecker.cpp revision e172e8b9e7fc67d7d03589af7e92fe777afcf33a
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 llvm::OwningPtr<BuiltinBug> BT_stackleak; 30 mutable llvm::OwningPtr<BuiltinBug> BT_returnstack; 31 32public: 33 void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const; 34 void checkEndPath(EndOfFunctionNodeBuilder &B, ExprEngine &Eng) 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 { 80 assert(false && "Invalid region in ReturnStackAddressChecker."); 81 } 82 83 return range; 84} 85 86void StackAddrEscapeChecker::EmitStackError(CheckerContext &C, const MemRegion *R, 87 const Expr *RetE) const { 88 ExplodedNode *N = C.generateSink(); 89 90 if (!N) 91 return; 92 93 if (!BT_returnstack) 94 BT_returnstack.reset( 95 new BuiltinBug("Return of address to stack-allocated memory")); 96 97 // Generate a report for this bug. 98 llvm::SmallString<512> buf; 99 llvm::raw_svector_ostream os(buf); 100 SourceRange range = GenName(os, R, C.getSourceManager()); 101 os << " returned to caller"; 102 BugReport *report = new BugReport(*BT_returnstack, os.str(), N); 103 report->addRange(RetE->getSourceRange()); 104 if (range.isValid()) 105 report->addRange(range); 106 107 C.EmitReport(report); 108} 109 110void StackAddrEscapeChecker::checkPreStmt(const ReturnStmt *RS, 111 CheckerContext &C) const { 112 113 const Expr *RetE = RS->getRetValue(); 114 if (!RetE) 115 return; 116 117 SVal V = C.getState()->getSVal(RetE); 118 const MemRegion *R = V.getAsRegion(); 119 120 if (!R || !R->hasStackStorage()) 121 return; 122 123 if (R->hasStackStorage()) { 124 // Automatic reference counting automatically copies blocks. 125 if (C.getASTContext().getLangOptions().ObjCAutoRefCount && 126 isa<BlockDataRegion>(R)) 127 return; 128 129 EmitStackError(C, R, RetE); 130 return; 131 } 132} 133 134void StackAddrEscapeChecker::checkEndPath(EndOfFunctionNodeBuilder &B, 135 ExprEngine &Eng) const { 136 137 const ProgramState *state = B.getState(); 138 139 // Iterate over all bindings to global variables and see if it contains 140 // a memory region in the stack space. 141 class CallBack : public StoreManager::BindingsHandler { 142 private: 143 ExprEngine &Eng; 144 const StackFrameContext *CurSFC; 145 public: 146 SmallVector<std::pair<const MemRegion*, const MemRegion*>, 10> V; 147 148 CallBack(ExprEngine &Eng, const LocationContext *LCtx) 149 : Eng(Eng), CurSFC(LCtx->getCurrentStackFrame()) {} 150 151 bool HandleBinding(StoreManager &SMgr, Store store, 152 const MemRegion *region, SVal val) { 153 154 if (!isa<GlobalsSpaceRegion>(region->getMemorySpace())) 155 return true; 156 157 const MemRegion *vR = val.getAsRegion(); 158 if (!vR) 159 return true; 160 161 // Under automated retain release, it is okay to assign a block 162 // directly to a global variable. 163 if (Eng.getContext().getLangOptions().ObjCAutoRefCount && 164 isa<BlockDataRegion>(vR)) 165 return true; 166 167 if (const StackSpaceRegion *SSR = 168 dyn_cast<StackSpaceRegion>(vR->getMemorySpace())) { 169 // If the global variable holds a location in the current stack frame, 170 // record the binding to emit a warning. 171 if (SSR->getStackFrame() == CurSFC) 172 V.push_back(std::make_pair(region, vR)); 173 } 174 175 return true; 176 } 177 }; 178 179 CallBack cb(Eng, B.getPredecessor()->getLocationContext()); 180 state->getStateManager().getStoreManager().iterBindings(state->getStore(),cb); 181 182 if (cb.V.empty()) 183 return; 184 185 // Generate an error node. 186 ExplodedNode *N = B.generateNode(state); 187 if (!N) 188 return; 189 190 if (!BT_stackleak) 191 BT_stackleak.reset( 192 new BuiltinBug("Stack address stored into global variable", 193 "Stack address was saved into a global variable. " 194 "This is dangerous because the address will become " 195 "invalid after returning from the function")); 196 197 for (unsigned i = 0, e = cb.V.size(); i != e; ++i) { 198 // Generate a report for this bug. 199 llvm::SmallString<512> buf; 200 llvm::raw_svector_ostream os(buf); 201 SourceRange range = GenName(os, cb.V[i].second, 202 Eng.getContext().getSourceManager()); 203 os << " is still referred to by the global variable '"; 204 const VarRegion *VR = cast<VarRegion>(cb.V[i].first->getBaseRegion()); 205 os << VR->getDecl()->getNameAsString() 206 << "' upon returning to the caller. This will be a dangling reference"; 207 BugReport *report = new BugReport(*BT_stackleak, os.str(), N); 208 if (range.isValid()) 209 report->addRange(range); 210 211 Eng.getBugReporter().EmitReport(report); 212 } 213} 214 215void ento::registerStackAddrEscapeChecker(CheckerManager &mgr) { 216 mgr.registerChecker<StackAddrEscapeChecker>(); 217} 218