StackAddrEscapeChecker.cpp revision 73212dff6437d409e0c1b779fdcac2f4f98ca8b0
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 RetE = RetE->IgnoreParens(); 122 123 const LocationContext *LCtx = C.getLocationContext(); 124 SVal V = C.getState()->getSVal(RetE, LCtx); 125 const MemRegion *R = V.getAsRegion(); 126 127 if (!R) 128 return; 129 130 const StackSpaceRegion *SS = 131 dyn_cast_or_null<StackSpaceRegion>(R->getMemorySpace()); 132 133 if (!SS) 134 return; 135 136 // Return stack memory in an ancestor stack frame is fine. 137 const StackFrameContext *CurFrame = LCtx->getCurrentStackFrame(); 138 const StackFrameContext *MemFrame = SS->getStackFrame(); 139 if (MemFrame != CurFrame) 140 return; 141 142 // Automatic reference counting automatically copies blocks. 143 if (C.getASTContext().getLangOpts().ObjCAutoRefCount && 144 isa<BlockDataRegion>(R)) 145 return; 146 147 // Returning a record by value is fine. (In this case, the returned 148 // expression will be a copy-constructor, possibly wrapped in an 149 // ExprWithCleanups node.) 150 if (const ExprWithCleanups *Cleanup = dyn_cast<ExprWithCleanups>(RetE)) 151 RetE = Cleanup->getSubExpr(); 152 if (isa<CXXConstructExpr>(RetE) && RetE->getType()->isRecordType()) 153 return; 154 155 EmitStackError(C, R, RetE); 156} 157 158void StackAddrEscapeChecker::checkEndPath(CheckerContext &Ctx) const { 159 ProgramStateRef state = Ctx.getState(); 160 161 // Iterate over all bindings to global variables and see if it contains 162 // a memory region in the stack space. 163 class CallBack : public StoreManager::BindingsHandler { 164 private: 165 CheckerContext &Ctx; 166 const StackFrameContext *CurSFC; 167 public: 168 SmallVector<std::pair<const MemRegion*, const MemRegion*>, 10> V; 169 170 CallBack(CheckerContext &CC) : 171 Ctx(CC), 172 CurSFC(CC.getLocationContext()->getCurrentStackFrame()) 173 {} 174 175 bool HandleBinding(StoreManager &SMgr, Store store, 176 const MemRegion *region, SVal val) { 177 178 if (!isa<GlobalsSpaceRegion>(region->getMemorySpace())) 179 return true; 180 181 const MemRegion *vR = val.getAsRegion(); 182 if (!vR) 183 return true; 184 185 // Under automated retain release, it is okay to assign a block 186 // directly to a global variable. 187 if (Ctx.getASTContext().getLangOpts().ObjCAutoRefCount && 188 isa<BlockDataRegion>(vR)) 189 return true; 190 191 if (const StackSpaceRegion *SSR = 192 dyn_cast<StackSpaceRegion>(vR->getMemorySpace())) { 193 // If the global variable holds a location in the current stack frame, 194 // record the binding to emit a warning. 195 if (SSR->getStackFrame() == CurSFC) 196 V.push_back(std::make_pair(region, vR)); 197 } 198 199 return true; 200 } 201 }; 202 203 CallBack cb(Ctx); 204 state->getStateManager().getStoreManager().iterBindings(state->getStore(),cb); 205 206 if (cb.V.empty()) 207 return; 208 209 // Generate an error node. 210 ExplodedNode *N = Ctx.addTransition(state); 211 if (!N) 212 return; 213 214 if (!BT_stackleak) 215 BT_stackleak.reset( 216 new BuiltinBug("Stack address stored into global variable", 217 "Stack address was saved into a global variable. " 218 "This is dangerous because the address will become " 219 "invalid after returning from the function")); 220 221 for (unsigned i = 0, e = cb.V.size(); i != e; ++i) { 222 // Generate a report for this bug. 223 SmallString<512> buf; 224 llvm::raw_svector_ostream os(buf); 225 SourceRange range = GenName(os, cb.V[i].second, 226 Ctx.getSourceManager()); 227 os << " is still referred to by the global variable '"; 228 const VarRegion *VR = cast<VarRegion>(cb.V[i].first->getBaseRegion()); 229 os << *VR->getDecl() 230 << "' upon returning to the caller. This will be a dangling reference"; 231 BugReport *report = new BugReport(*BT_stackleak, os.str(), N); 232 if (range.isValid()) 233 report->addRange(range); 234 235 Ctx.EmitReport(report); 236 } 237} 238 239void ento::registerStackAddrEscapeChecker(CheckerManager &mgr) { 240 mgr.registerChecker<StackAddrEscapeChecker>(); 241} 242