Google Git
Sign in
android / platform / external / clang / cde8cdbd6a662c636164465ad309b5f17ff01064 / . / lib / StaticAnalyzer / Checkers / MallocChecker.cpp
blob: 2c960921a429236c9e351895b8b738c900f6a898 [file] [log] [blame]
//=== MallocChecker.cpp - A malloc/free checker -------------------*- C++ -*--//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines malloc/free checker, which checks for potential memory
// leaks, double free, and use-after-free problems.
//
//===----------------------------------------------------------------------===//
#include "ClangSACheckers.h"
#include "InterCheckerAPI.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/Calls.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
#include "clang/Basic/SourceManager.h"
#include "llvm/ADT/ImmutableMap.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/STLExtras.h"
#include <climits>
using namespace clang;
using namespace ento;
namespace {
class RefState {
enum Kind { // Reference to allocated memory.
Allocated,
// Reference to released/freed memory.
Released,
// Reference to escaped memory - no assumptions can be made of
// the state after the reference escapes.
Escaped,
// The responsibility for freeing resources has transfered from
// this reference. A relinquished symbol should not be freed.
Relinquished } K;
const Stmt *S;
public:
RefState(Kind k, const Stmt *s) : K(k), S(s) {}
bool isAllocated() const { return K == Allocated; }
bool isReleased() const { return K == Released; }
bool isRelinquished() const { return K == Relinquished; }
const Stmt *getStmt() const { return S; }
bool operator==(const RefState &X) const {
return K == X.K && S == X.S;
}
static RefState getAllocated(const Stmt *s) {
return RefState(Allocated, s);
}
static RefState getReleased(const Stmt *s) { return RefState(Released, s); }
static RefState getEscaped(const Stmt *s) { return RefState(Escaped, s); }
static RefState getRelinquished(const Stmt *s) {
return RefState(Relinquished, s);
}
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.AddInteger(K);
ID.AddPointer(S);
}
};
struct ReallocPair {
SymbolRef ReallocatedSym;
bool IsFreeOnFailure;
ReallocPair(SymbolRef S, bool F) : ReallocatedSym(S), IsFreeOnFailure(F) {}
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.AddInteger(IsFreeOnFailure);
ID.AddPointer(ReallocatedSym);
}
bool operator==(const ReallocPair &X) const {
return ReallocatedSym == X.ReallocatedSym &&
IsFreeOnFailure == X.IsFreeOnFailure;
}
};
typedef std::pair<const Stmt*, const MemRegion*> LeakInfo;
class MallocChecker : public Checker<check::DeadSymbols,
check::EndPath,
check::PreStmt<ReturnStmt>,
check::PreStmt<CallExpr>,
check::PostStmt<CallExpr>,
check::PostStmt<BlockExpr>,
check::PreObjCMessage,
check::Location,
check::Bind,
eval::Assume,
check::RegionChanges>
{
mutable OwningPtr<BugType> BT_DoubleFree;
mutable OwningPtr<BugType> BT_Leak;
mutable OwningPtr<BugType> BT_UseFree;
mutable OwningPtr<BugType> BT_BadFree;
mutable IdentifierInfo *II_malloc, *II_free, *II_realloc, *II_calloc,
*II_valloc, *II_reallocf, *II_strndup, *II_strdup;
public:
MallocChecker() : II_malloc(0), II_free(0), II_realloc(0), II_calloc(0),
II_valloc(0), II_reallocf(0), II_strndup(0), II_strdup(0) {}
/// In pessimistic mode, the checker assumes that it does not know which
/// functions might free the memory.
struct ChecksFilter {
DefaultBool CMallocPessimistic;
DefaultBool CMallocOptimistic;
};
ChecksFilter Filter;
void checkPreStmt(const CallExpr *S, CheckerContext &C) const;
void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
void checkPreObjCMessage(const ObjCMessage &Msg, CheckerContext &C) const;
void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
void checkEndPath(CheckerContext &C) const;
void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
bool Assumption) const;
void checkLocation(SVal l, bool isLoad, const Stmt *S,
CheckerContext &C) const;
void checkBind(SVal location, SVal val, const Stmt*S,
CheckerContext &C) const;
ProgramStateRef
checkRegionChanges(ProgramStateRef state,
const StoreManager::InvalidatedSymbols *invalidated,
ArrayRef<const MemRegion *> ExplicitRegions,
ArrayRef<const MemRegion *> Regions,
const CallEvent *Call) const;
bool wantsRegionChangeUpdate(ProgramStateRef state) const {
return true;
}
void printState(raw_ostream &Out, ProgramStateRef State,
const char *NL, const char *Sep) const;
private:
void initIdentifierInfo(ASTContext &C) const;
/// Check if this is one of the functions which can allocate/reallocate memory
/// pointed to by one of its arguments.
bool isMemFunction(const FunctionDecl *FD, ASTContext &C) const;
bool isFreeFunction(const FunctionDecl *FD, ASTContext &C) const;
bool isAllocationFunction(const FunctionDecl *FD, ASTContext &C) const;
static ProgramStateRef MallocMemReturnsAttr(CheckerContext &C,
const CallExpr *CE,
const OwnershipAttr* Att);
static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
const Expr *SizeEx, SVal Init,
ProgramStateRef state) {
return MallocMemAux(C, CE,
state->getSVal(SizeEx, C.getLocationContext()),
Init, state);
}
static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
SVal SizeEx, SVal Init,
ProgramStateRef state);
/// Update the RefState to reflect the new memory allocation.
static ProgramStateRef MallocUpdateRefState(CheckerContext &C,
const CallExpr *CE,
ProgramStateRef state);
ProgramStateRef FreeMemAttr(CheckerContext &C, const CallExpr *CE,
const OwnershipAttr* Att) const;
ProgramStateRef FreeMemAux(CheckerContext &C, const CallExpr *CE,
ProgramStateRef state, unsigned Num,
bool Hold) const;
ProgramStateRef FreeMemAux(CheckerContext &C, const Expr *Arg,
const Expr *ParentExpr,
ProgramStateRef state,
bool Hold) const;
ProgramStateRef ReallocMem(CheckerContext &C, const CallExpr *CE,
bool FreesMemOnFailure) const;
static ProgramStateRef CallocMem(CheckerContext &C, const CallExpr *CE);
///\brief Check if the memory associated with this symbol was released.
bool isReleased(SymbolRef Sym, CheckerContext &C) const;
bool checkEscape(SymbolRef Sym, const Stmt *S, CheckerContext &C) const;
bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
const Stmt *S = 0) const;
/// Check if the function is not known to us. So, for example, we could
/// conservatively assume it can free/reallocate it's pointer arguments.
bool doesNotFreeMemory(const CallEvent *Call,
ProgramStateRef State) const;
static bool SummarizeValue(raw_ostream &os, SVal V);
static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR);
void ReportBadFree(CheckerContext &C, SVal ArgVal, SourceRange range) const;
/// Find the location of the allocation for Sym on the path leading to the
/// exploded node N.
LeakInfo getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
CheckerContext &C) const;
void reportLeak(SymbolRef Sym, ExplodedNode *N, CheckerContext &C) const;
/// The bug visitor which allows us to print extra diagnostics along the
/// BugReport path. For example, showing the allocation site of the leaked
/// region.
class MallocBugVisitor : public BugReporterVisitorImpl<MallocBugVisitor> {
protected:
enum NotificationMode {
Normal,
ReallocationFailed
};
// The allocated region symbol tracked by the main analysis.
SymbolRef Sym;
// The mode we are in, i.e. what kind of diagnostics will be emitted.
NotificationMode Mode;
// A symbol from when the primary region should have been reallocated.
SymbolRef FailedReallocSymbol;
bool IsLeak;
public:
MallocBugVisitor(SymbolRef S, bool isLeak = false)
: Sym(S), Mode(Normal), FailedReallocSymbol(0), IsLeak(isLeak) {}
virtual ~MallocBugVisitor() {}
void Profile(llvm::FoldingSetNodeID &ID) const {
static int X = 0;
ID.AddPointer(&X);
ID.AddPointer(Sym);
}
inline bool isAllocated(const RefState *S, const RefState *SPrev,
const Stmt *Stmt) {
// Did not track -> allocated. Other state (released) -> allocated.
return (Stmt && isa<CallExpr>(Stmt) &&
(S && S->isAllocated()) && (!SPrev || !SPrev->isAllocated()));
}
inline bool isReleased(const RefState *S, const RefState *SPrev,
const Stmt *Stmt) {
// Did not track -> released. Other state (allocated) -> released.
return (Stmt && isa<CallExpr>(Stmt) &&
(S && S->isReleased()) && (!SPrev || !SPrev->isReleased()));
}
inline bool isRelinquished(const RefState *S, const RefState *SPrev,
const Stmt *Stmt) {
// Did not track -> relinquished. Other state (allocated) -> relinquished.
return (Stmt && (isa<CallExpr>(Stmt) || isa<ObjCMessageExpr>(Stmt) ||
isa<ObjCPropertyRefExpr>(Stmt)) &&
(S && S->isRelinquished()) &&
(!SPrev || !SPrev->isRelinquished()));
}
inline bool isReallocFailedCheck(const RefState *S, const RefState *SPrev,
const Stmt *Stmt) {
// If the expression is not a call, and the state change is
// released -> allocated, it must be the realloc return value
// check. If we have to handle more cases here, it might be cleaner just
// to track this extra bit in the state itself.
return ((!Stmt || !isa<CallExpr>(Stmt)) &&
(S && S->isAllocated()) && (SPrev && !SPrev->isAllocated()));
}
PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
const ExplodedNode *PrevN,
BugReporterContext &BRC,
BugReport &BR);
PathDiagnosticPiece* getEndPath(BugReporterContext &BRC,
const ExplodedNode *EndPathNode,
BugReport &BR) {
if (!IsLeak)
return 0;
PathDiagnosticLocation L =
PathDiagnosticLocation::createEndOfPath(EndPathNode,
BRC.getSourceManager());
// Do not add the statement itself as a range in case of leak.
return new PathDiagnosticEventPiece(L, BR.getDescription(), false);
}
private:
class StackHintGeneratorForReallocationFailed
: public StackHintGeneratorForSymbol {
public:
StackHintGeneratorForReallocationFailed(SymbolRef S, StringRef M)
: StackHintGeneratorForSymbol(S, M) {}
virtual std::string getMessageForArg(const Expr *ArgE, unsigned ArgIndex) {
SmallString<200> buf;
llvm::raw_svector_ostream os(buf);
os << "Reallocation of ";
// Printed parameters start at 1, not 0.
printOrdinal(++ArgIndex, os);
os << " parameter failed";
return os.str();
}
virtual std::string getMessageForReturn(const CallExpr *CallExpr) {
return "Reallocation of returned value failed";
}
};
};
};
} // end anonymous namespace
typedef llvm::ImmutableMap<SymbolRef, RefState> RegionStateTy;
typedef llvm::ImmutableMap<SymbolRef, ReallocPair > ReallocMap;
class RegionState {};
class ReallocPairs {};
namespace clang {
namespace ento {
template <>
struct ProgramStateTrait<RegionState>
: public ProgramStatePartialTrait<RegionStateTy> {
static void *GDMIndex() { static int x; return &x; }
};
template <>
struct ProgramStateTrait<ReallocPairs>
: public ProgramStatePartialTrait<ReallocMap> {
static void *GDMIndex() { static int x; return &x; }
};
}
}
namespace {
class StopTrackingCallback : public SymbolVisitor {
ProgramStateRef state;
public:
StopTrackingCallback(ProgramStateRef st) : state(st) {}
ProgramStateRef getState() const { return state; }
bool VisitSymbol(SymbolRef sym) {
state = state->remove<RegionState>(sym);
return true;
}
};
} // end anonymous namespace
void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const {
if (II_malloc)
return;
II_malloc = &Ctx.Idents.get("malloc");
II_free = &Ctx.Idents.get("free");
II_realloc = &Ctx.Idents.get("realloc");
II_reallocf = &Ctx.Idents.get("reallocf");
II_calloc = &Ctx.Idents.get("calloc");
II_valloc = &Ctx.Idents.get("valloc");
II_strdup = &Ctx.Idents.get("strdup");
II_strndup = &Ctx.Idents.get("strndup");
}
bool MallocChecker::isMemFunction(const FunctionDecl *FD, ASTContext &C) const {
if (isFreeFunction(FD, C))
return true;
if (isAllocationFunction(FD, C))
return true;
return false;
}
bool MallocChecker::isAllocationFunction(const FunctionDecl *FD,
ASTContext &C) const {
if (!FD)
return false;
IdentifierInfo *FunI = FD->getIdentifier();
if (!FunI)
return false;
initIdentifierInfo(C);
if (FunI == II_malloc || FunI == II_realloc ||
FunI == II_reallocf || FunI == II_calloc || FunI == II_valloc ||
FunI == II_strdup || FunI == II_strndup)
return true;
if (Filter.CMallocOptimistic && FD->hasAttrs())
for (specific_attr_iterator<OwnershipAttr>
i = FD->specific_attr_begin<OwnershipAttr>(),
e = FD->specific_attr_end<OwnershipAttr>();
i != e; ++i)
if ((*i)->getOwnKind() == OwnershipAttr::Returns)
return true;
return false;
}
bool MallocChecker::isFreeFunction(const FunctionDecl *FD, ASTContext &C) const {
if (!FD)
return false;
IdentifierInfo *FunI = FD->getIdentifier();
if (!FunI)
return false;
initIdentifierInfo(C);
if (FunI == II_free || FunI == II_realloc || FunI == II_reallocf)
return true;
if (Filter.CMallocOptimistic && FD->hasAttrs())
for (specific_attr_iterator<OwnershipAttr>
i = FD->specific_attr_begin<OwnershipAttr>(),
e = FD->specific_attr_end<OwnershipAttr>();
i != e; ++i)
if ((*i)->getOwnKind() == OwnershipAttr::Takes ||
(*i)->getOwnKind() == OwnershipAttr::Holds)
return true;
return false;
}
void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
const FunctionDecl *FD = C.getCalleeDecl(CE);
if (!FD)
return;
initIdentifierInfo(C.getASTContext());
IdentifierInfo *FunI = FD->getIdentifier();
if (!FunI)
return;
ProgramStateRef State = C.getState();
if (FunI == II_malloc || FunI == II_valloc) {
if (CE->getNumArgs() < 1)
return;
State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State);
} else if (FunI == II_realloc) {
State = ReallocMem(C, CE, false);
} else if (FunI == II_reallocf) {
State = ReallocMem(C, CE, true);
} else if (FunI == II_calloc) {
State = CallocMem(C, CE);
} else if (FunI == II_free) {
State = FreeMemAux(C, CE, C.getState(), 0, false);
} else if (FunI == II_strdup) {
State = MallocUpdateRefState(C, CE, State);
} else if (FunI == II_strndup) {
State = MallocUpdateRefState(C, CE, State);
} else if (Filter.CMallocOptimistic) {
// Check all the attributes, if there are any.
// There can be multiple of these attributes.
if (FD->hasAttrs())
for (specific_attr_iterator<OwnershipAttr>
i = FD->specific_attr_begin<OwnershipAttr>(),
e = FD->specific_attr_end<OwnershipAttr>();
i != e; ++i) {
switch ((*i)->getOwnKind()) {
case OwnershipAttr::Returns:
State = MallocMemReturnsAttr(C, CE, *i);
break;
case OwnershipAttr::Takes:
case OwnershipAttr::Holds:
State = FreeMemAttr(C, CE, *i);
break;
}
}
}
C.addTransition(State);
}
static bool isFreeWhenDoneSetToZero(const ObjCMethodCall &Call) {
Selector S = Call.getSelector();
for (unsigned i = 1; i < S.getNumArgs(); ++i)
if (S.getNameForSlot(i).equals("freeWhenDone"))
if (Call.getArgSVal(i).isConstant(0))
return true;
return false;
}
void MallocChecker::checkPreObjCMessage(const ObjCMessage &Msg,
CheckerContext &C) const {
const ObjCMethodDecl *MD = Msg.getMethodDecl();
if (!MD)
return;
// FIXME: ObjCMessage is going away soon.
ObjCMessageSend Call(Msg.getMessageExpr(), C.getState(),
C.getLocationContext());
Selector S = Msg.getSelector();
// If the first selector is dataWithBytesNoCopy, assume that the memory will
// be released with 'free' by the new object.
// Ex: [NSData dataWithBytesNoCopy:bytes length:10];
// Unless 'freeWhenDone' param set to 0.
// TODO: Check that the memory was allocated with malloc.
if ((S.getNameForSlot(0) == "dataWithBytesNoCopy" ||
S.getNameForSlot(0) == "initWithBytesNoCopy" ||
S.getNameForSlot(0) == "initWithCharactersNoCopy") &&
!isFreeWhenDoneSetToZero(Call)){
unsigned int argIdx = 0;
C.addTransition(FreeMemAux(C, Call.getArgExpr(argIdx),
Msg.getMessageExpr(), C.getState(), true));
}
}
ProgramStateRef MallocChecker::MallocMemReturnsAttr(CheckerContext &C,
const CallExpr *CE,
const OwnershipAttr* Att) {
if (Att->getModule() != "malloc")
return 0;
OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
if (I != E) {
return MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState());
}
return MallocMemAux(C, CE, UnknownVal(), UndefinedVal(), C.getState());
}
ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
const CallExpr *CE,
SVal Size, SVal Init,
ProgramStateRef state) {
// Bind the return value to the symbolic value from the heap region.
// TODO: We could rewrite post visit to eval call; 'malloc' does not have
// side effects other than what we model here.
unsigned Count = C.getCurrentBlockCount();
SValBuilder &svalBuilder = C.getSValBuilder();
const LocationContext *LCtx = C.getPredecessor()->getLocationContext();
DefinedSVal RetVal =
cast<DefinedSVal>(svalBuilder.getConjuredHeapSymbolVal(CE, LCtx, Count));
state = state->BindExpr(CE, C.getLocationContext(), RetVal);
// We expect the malloc functions to return a pointer.
if (!isa<Loc>(RetVal))
return 0;
// Fill the region with the initialization value.
state = state->bindDefault(RetVal, Init);
// Set the region's extent equal to the Size parameter.
const SymbolicRegion *R =
dyn_cast_or_null<SymbolicRegion>(RetVal.getAsRegion());
if (!R)
return 0;
if (isa<DefinedOrUnknownSVal>(Size)) {
SValBuilder &svalBuilder = C.getSValBuilder();
DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size);
DefinedOrUnknownSVal extentMatchesSize =
svalBuilder.evalEQ(state, Extent, DefinedSize);
state = state->assume(extentMatchesSize, true);
assert(state);
}
return MallocUpdateRefState(C, CE, state);
}
ProgramStateRef MallocChecker::MallocUpdateRefState(CheckerContext &C,
const CallExpr *CE,
ProgramStateRef state) {
// Get the return value.
SVal retVal = state->getSVal(CE, C.getLocationContext());
// We expect the malloc functions to return a pointer.
if (!isa<Loc>(retVal))
return 0;
SymbolRef Sym = retVal.getAsLocSymbol();
assert(Sym);
// Set the symbol's state to Allocated.
return state->set<RegionState>(Sym, RefState::getAllocated(CE));
}
ProgramStateRef MallocChecker::FreeMemAttr(CheckerContext &C,
const CallExpr *CE,
const OwnershipAttr* Att) const {
if (Att->getModule() != "malloc")
return 0;
ProgramStateRef State = C.getState();
for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
I != E; ++I) {
ProgramStateRef StateI = FreeMemAux(C, CE, State, *I,
Att->getOwnKind() == OwnershipAttr::Holds);
if (StateI)
State = StateI;
}
return State;
}
ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
const CallExpr *CE,
ProgramStateRef state,
unsigned Num,
bool Hold) const {
if (CE->getNumArgs() < (Num + 1))
return 0;
return FreeMemAux(C, CE->getArg(Num), CE, state, Hold);
}
ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
const Expr *ArgExpr,
const Expr *ParentExpr,
ProgramStateRef state,
bool Hold) const {
SVal ArgVal = state->getSVal(ArgExpr, C.getLocationContext());
if (!isa<DefinedOrUnknownSVal>(ArgVal))
return 0;
DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal);
// Check for null dereferences.
if (!isa<Loc>(location))
return 0;
// The explicit NULL case, no operation is performed.
ProgramStateRef notNullState, nullState;
llvm::tie(notNullState, nullState) = state->assume(location);
if (nullState && !notNullState)
return 0;
// Unknown values could easily be okay
// Undefined values are handled elsewhere
if (ArgVal.isUnknownOrUndef())
return 0;
const MemRegion *R = ArgVal.getAsRegion();
// Nonlocs can't be freed, of course.
// Non-region locations (labels and fixed addresses) also shouldn't be freed.
if (!R) {
ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
return 0;
}
R = R->StripCasts();
// Blocks might show up as heap data, but should not be free()d
if (isa<BlockDataRegion>(R)) {
ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
return 0;
}
const MemSpaceRegion *MS = R->getMemorySpace();
// Parameters, locals, statics, and globals shouldn't be freed.
if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) {
// FIXME: at the time this code was written, malloc() regions were
// represented by conjured symbols, which are all in UnknownSpaceRegion.
// This means that there isn't actually anything from HeapSpaceRegion
// that should be freed, even though we allow it here.
// Of course, free() can work on memory allocated outside the current
// function, so UnknownSpaceRegion is always a possibility.
// False negatives are better than false positives.
ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
return 0;
}
const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
// Various cases could lead to non-symbol values here.
// For now, ignore them.
if (!SR)
return 0;
SymbolRef Sym = SR->getSymbol();
const RefState *RS = state->get<RegionState>(Sym);
// If the symbol has not been tracked, return. This is possible when free() is
// called on a pointer that does not get its pointee directly from malloc().
// Full support of this requires inter-procedural analysis.
if (!RS)
return 0;
// Check double free.
if (RS->isReleased() || RS->isRelinquished()) {
if (ExplodedNode *N = C.generateSink()) {
if (!BT_DoubleFree)
BT_DoubleFree.reset(
new BugType("Double free", "Memory Error"));
BugReport *R = new BugReport(*BT_DoubleFree,
(RS->isReleased() ? "Attempt to free released memory" :
"Attempt to free non-owned memory"), N);
R->addRange(ArgExpr->getSourceRange());
R->markInteresting(Sym);
R->addVisitor(new MallocBugVisitor(Sym));
C.EmitReport(R);
}
return 0;
}
// Normal free.
if (Hold)
return state->set<RegionState>(Sym, RefState::getRelinquished(ParentExpr));
return state->set<RegionState>(Sym, RefState::getReleased(ParentExpr));
}
bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V))
os << "an integer (" << IntVal->getValue() << ")";
else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V))
os << "a constant address (" << ConstAddr->getValue() << ")";
else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V))
os << "the address of the label '" << Label->getLabel()->getName() << "'";
else
return false;
return true;
}
bool MallocChecker::SummarizeRegion(raw_ostream &os,
const MemRegion *MR) {
switch (MR->getKind()) {
case MemRegion::FunctionTextRegionKind: {
const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
if (FD)
os << "the address of the function '" << *FD << '\'';
else
os << "the address of a function";
return true;
}
case MemRegion::BlockTextRegionKind:
os << "block text";
return true;
case MemRegion::BlockDataRegionKind:
// FIXME: where the block came from?
os << "a block";
return true;
default: {
const MemSpaceRegion *MS = MR->getMemorySpace();
if (isa<StackLocalsSpaceRegion>(MS)) {
const VarRegion *VR = dyn_cast<VarRegion>(MR);
const VarDecl *VD;
if (VR)
VD = VR->getDecl();
else
VD = NULL;
if (VD)
os << "the address of the local variable '" << VD->getName() << "'";
else
os << "the address of a local stack variable";
return true;
}
if (isa<StackArgumentsSpaceRegion>(MS)) {
const VarRegion *VR = dyn_cast<VarRegion>(MR);
const VarDecl *VD;
if (VR)
VD = VR->getDecl();
else
VD = NULL;
if (VD)
os << "the address of the parameter '" << VD->getName() << "'";
else
os << "the address of a parameter";
return true;
}
if (isa<GlobalsSpaceRegion>(MS)) {
const VarRegion *VR = dyn_cast<VarRegion>(MR);
const VarDecl *VD;
if (VR)
VD = VR->getDecl();
else
VD = NULL;
if (VD) {
if (VD->isStaticLocal())
os << "the address of the static variable '" << VD->getName() << "'";
else
os << "the address of the global variable '" << VD->getName() << "'";
} else
os << "the address of a global variable";
return true;
}
return false;
}
}
}
void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal,
SourceRange range) const {
if (ExplodedNode *N = C.generateSink()) {
if (!BT_BadFree)
BT_BadFree.reset(new BugType("Bad free", "Memory Error"));
SmallString<100> buf;
llvm::raw_svector_ostream os(buf);
const MemRegion *MR = ArgVal.getAsRegion();
if (MR) {
while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR))
MR = ER->getSuperRegion();
// Special case for alloca()
if (isa<AllocaRegion>(MR))
os << "Argument to free() was allocated by alloca(), not malloc()";
else {
os << "Argument to free() is ";
if (SummarizeRegion(os, MR))
os << ", which is not memory allocated by malloc()";
else
os << "not memory allocated by malloc()";
}
} else {
os << "Argument to free() is ";
if (SummarizeValue(os, ArgVal))
os << ", which is not memory allocated by malloc()";
else
os << "not memory allocated by malloc()";
}
BugReport *R = new BugReport(*BT_BadFree, os.str(), N);
R->markInteresting(MR);
R->addRange(range);
C.EmitReport(R);
}
}
ProgramStateRef MallocChecker::ReallocMem(CheckerContext &C,
const CallExpr *CE,
bool FreesOnFail) const {
if (CE->getNumArgs() < 2)
return 0;
ProgramStateRef state = C.getState();
const Expr *arg0Expr = CE->getArg(0);
const LocationContext *LCtx = C.getLocationContext();
SVal Arg0Val = state->getSVal(arg0Expr, LCtx);
if (!isa<DefinedOrUnknownSVal>(Arg0Val))
return 0;
DefinedOrUnknownSVal arg0Val = cast<DefinedOrUnknownSVal>(Arg0Val);
SValBuilder &svalBuilder = C.getSValBuilder();
DefinedOrUnknownSVal PtrEQ =
svalBuilder.evalEQ(state, arg0Val, svalBuilder.makeNull());
// Get the size argument. If there is no size arg then give up.
const Expr *Arg1 = CE->getArg(1);
if (!Arg1)
return 0;
// Get the value of the size argument.
SVal Arg1ValG = state->getSVal(Arg1, LCtx);
if (!isa<DefinedOrUnknownSVal>(Arg1ValG))
return 0;
DefinedOrUnknownSVal Arg1Val = cast<DefinedOrUnknownSVal>(Arg1ValG);
// Compare the size argument to 0.
DefinedOrUnknownSVal SizeZero =
svalBuilder.evalEQ(state, Arg1Val,
svalBuilder.makeIntValWithPtrWidth(0, false));
ProgramStateRef StatePtrIsNull, StatePtrNotNull;
llvm::tie(StatePtrIsNull, StatePtrNotNull) = state->assume(PtrEQ);
ProgramStateRef StateSizeIsZero, StateSizeNotZero;
llvm::tie(StateSizeIsZero, StateSizeNotZero) = state->assume(SizeZero);
// We only assume exceptional states if they are definitely true; if the
// state is under-constrained, assume regular realloc behavior.
bool PrtIsNull = StatePtrIsNull && !StatePtrNotNull;
bool SizeIsZero = StateSizeIsZero && !StateSizeNotZero;
// If the ptr is NULL and the size is not 0, the call is equivalent to
// malloc(size).
if ( PrtIsNull && !SizeIsZero) {
ProgramStateRef stateMalloc = MallocMemAux(C, CE, CE->getArg(1),
UndefinedVal(), StatePtrIsNull);
return stateMalloc;
}
if (PrtIsNull && SizeIsZero)
return 0;
// Get the from and to pointer symbols as in toPtr = realloc(fromPtr, size).
assert(!PrtIsNull);
SymbolRef FromPtr = arg0Val.getAsSymbol();
SVal RetVal = state->getSVal(CE, LCtx);
SymbolRef ToPtr = RetVal.getAsSymbol();
if (!FromPtr || !ToPtr)
return 0;
// If the size is 0, free the memory.
if (SizeIsZero)
if (ProgramStateRef stateFree = FreeMemAux(C, CE, StateSizeIsZero,0,false)){
// The semantics of the return value are:
// If size was equal to 0, either NULL or a pointer suitable to be passed
// to free() is returned.
stateFree = stateFree->set<ReallocPairs>(ToPtr,
ReallocPair(FromPtr, FreesOnFail));
C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
return stateFree;
}
// Default behavior.
if (ProgramStateRef stateFree = FreeMemAux(C, CE, state, 0, false)) {
// FIXME: We should copy the content of the original buffer.
ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1),
UnknownVal(), stateFree);
if (!stateRealloc)
return 0;
stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr,
ReallocPair(FromPtr, FreesOnFail));
C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
return stateRealloc;
}
return 0;
}
ProgramStateRef MallocChecker::CallocMem(CheckerContext &C, const CallExpr *CE){
if (CE->getNumArgs() < 2)
return 0;
ProgramStateRef state = C.getState();
SValBuilder &svalBuilder = C.getSValBuilder();
const LocationContext *LCtx = C.getLocationContext();
SVal count = state->getSVal(CE->getArg(0), LCtx);
SVal elementSize = state->getSVal(CE->getArg(1), LCtx);
SVal TotalSize = svalBuilder.evalBinOp(state, BO_Mul, count, elementSize,
svalBuilder.getContext().getSizeType());
SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
return MallocMemAux(C, CE, TotalSize, zeroVal, state);
}
LeakInfo
MallocChecker::getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
CheckerContext &C) const {
const LocationContext *LeakContext = N->getLocationContext();
// Walk the ExplodedGraph backwards and find the first node that referred to
// the tracked symbol.
const ExplodedNode *AllocNode = N;
const MemRegion *ReferenceRegion = 0;
while (N) {
ProgramStateRef State = N->getState();
if (!State->get<RegionState>(Sym))
break;
// Find the most recent expression bound to the symbol in the current
// context.
if (!ReferenceRegion) {
if (const MemRegion *MR = C.getLocationRegionIfPostStore(N)) {
SVal Val = State->getSVal(MR);
if (Val.getAsLocSymbol() == Sym)
ReferenceRegion = MR;
}
}
// Allocation node, is the last node in the current context in which the
// symbol was tracked.
if (N->getLocationContext() == LeakContext)
AllocNode = N;
N = N->pred_empty() ? NULL : *(N->pred_begin());
}
ProgramPoint P = AllocNode->getLocation();
const Stmt *AllocationStmt = 0;
if (isa<StmtPoint>(P))
AllocationStmt = cast<StmtPoint>(P).getStmt();
return LeakInfo(AllocationStmt, ReferenceRegion);
}
void MallocChecker::reportLeak(SymbolRef Sym, ExplodedNode *N,
CheckerContext &C) const {
assert(N);
if (!BT_Leak) {
BT_Leak.reset(new BugType("Memory leak", "Memory Error"));
// Leaks should not be reported if they are post-dominated by a sink:
// (1) Sinks are higher importance bugs.
// (2) NoReturnFunctionChecker uses sink nodes to represent paths ending
// with __noreturn functions such as assert() or exit(). We choose not
// to report leaks on such paths.
BT_Leak->setSuppressOnSink(true);
}
// Most bug reports are cached at the location where they occurred.
// With leaks, we want to unique them by the location where they were
// allocated, and only report a single path.
PathDiagnosticLocation LocUsedForUniqueing;
const Stmt *AllocStmt = 0;
const MemRegion *Region = 0;
llvm::tie(AllocStmt, Region) = getAllocationSite(N, Sym, C);
if (AllocStmt)
LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
C.getSourceManager(), N->getLocationContext());
SmallString<200> buf;
llvm::raw_svector_ostream os(buf);
os << "Memory is never released; potential leak";
if (Region) {
os << " of memory pointed to by '";
Region->dumpPretty(os);
os <<'\'';
}
BugReport *R = new BugReport(*BT_Leak, os.str(), N, LocUsedForUniqueing);
R->markInteresting(Sym);
R->addVisitor(new MallocBugVisitor(Sym, true));
C.EmitReport(R);
}
void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
CheckerContext &C) const
{
if (!SymReaper.hasDeadSymbols())
return;
ProgramStateRef state = C.getState();
RegionStateTy RS = state->get<RegionState>();
RegionStateTy::Factory &F = state->get_context<RegionState>();
bool generateReport = false;
llvm::SmallVector<SymbolRef, 2> Errors;
for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
if (SymReaper.isDead(I->first)) {
if (I->second.isAllocated()) {
generateReport = true;
Errors.push_back(I->first);
}
// Remove the dead symbol from the map.
RS = F.remove(RS, I->first);
}
}
// Cleanup the Realloc Pairs Map.
ReallocMap RP = state->get<ReallocPairs>();
for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
if (SymReaper.isDead(I->first) ||
SymReaper.isDead(I->second.ReallocatedSym)) {
state = state->remove<ReallocPairs>(I->first);
}
}
// Generate leak node.
static SimpleProgramPointTag Tag("MallocChecker : DeadSymbolsLeak");
ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
if (generateReport) {
for (llvm::SmallVector<SymbolRef, 2>::iterator
I = Errors.begin(), E = Errors.end(); I != E; ++I) {
reportLeak(*I, N, C);
}
}
C.addTransition(state->set<RegionState>(RS), N);
}
void MallocChecker::checkEndPath(CheckerContext &C) const {
ProgramStateRef state = C.getState();
RegionStateTy M = state->get<RegionState>();
// If inside inlined call, skip it.
if (C.getLocationContext()->getParent() != 0)
return;
for (RegionStateTy::iterator I = M.begin(), E = M.end(); I != E; ++I) {
RefState RS = I->second;
if (RS.isAllocated()) {
ExplodedNode *N = C.addTransition(state);
if (N)
reportLeak(I->first, N, C);
}
}
}
bool MallocChecker::checkEscape(SymbolRef Sym, const Stmt *S,
CheckerContext &C) const {
ProgramStateRef state = C.getState();
const RefState *RS = state->get<RegionState>(Sym);
if (!RS)
return false;
if (RS->isAllocated()) {
state = state->set<RegionState>(Sym, RefState::getEscaped(S));
C.addTransition(state);
return true;
}
return false;
}
void MallocChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
// We will check for double free in the post visit.
if (isFreeFunction(C.getCalleeDecl(CE), C.getASTContext()))
return;
// Check use after free, when a freed pointer is passed to a call.
ProgramStateRef State = C.getState();
for (CallExpr::const_arg_iterator I = CE->arg_begin(),
E = CE->arg_end(); I != E; ++I) {
const Expr *A = *I;
if (A->getType().getTypePtr()->isAnyPointerType()) {
SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol();
if (!Sym)
continue;
if (checkUseAfterFree(Sym, C, A))
return;
}
}
}
void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
const Expr *E = S->getRetValue();
if (!E)
return;
// Check if we are returning a symbol.
SVal RetVal = C.getState()->getSVal(E, C.getLocationContext());
SymbolRef Sym = RetVal.getAsSymbol();
if (!Sym)
// If we are returning a field of the allocated struct or an array element,
// the callee could still free the memory.
// TODO: This logic should be a part of generic symbol escape callback.
if (const MemRegion *MR = RetVal.getAsRegion())
if (isa<FieldRegion>(MR) || isa<ElementRegion>(MR))
if (const SymbolicRegion *BMR =
dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
Sym = BMR->getSymbol();
if (!Sym)
return;
// Check if we are returning freed memory.
if (checkUseAfterFree(Sym, C, E))
return;
// If this function body is not inlined, check if the symbol is escaping.
if (C.getLocationContext()->getParent() == 0)
checkEscape(Sym, E, C);
}
// TODO: Blocks should be either inlined or should call invalidate regions
// upon invocation. After that's in place, special casing here will not be
// needed.
void MallocChecker::checkPostStmt(const BlockExpr *BE,
CheckerContext &C) const {
// Scan the BlockDecRefExprs for any object the retain count checker
// may be tracking.
if (!BE->getBlockDecl()->hasCaptures())
return;
ProgramStateRef state = C.getState();
const BlockDataRegion *R =
cast<BlockDataRegion>(state->getSVal(BE,
C.getLocationContext()).getAsRegion());
BlockDataRegion::referenced_vars_iterator I = R->referenced_vars_begin(),
E = R->referenced_vars_end();
if (I == E)
return;
SmallVector<const MemRegion*, 10> Regions;
const LocationContext *LC = C.getLocationContext();
MemRegionManager &MemMgr = C.getSValBuilder().getRegionManager();
for ( ; I != E; ++I) {
const VarRegion *VR = *I;
if (VR->getSuperRegion() == R) {
VR = MemMgr.getVarRegion(VR->getDecl(), LC);
}
Regions.push_back(VR);
}
state =
state->scanReachableSymbols<StopTrackingCallback>(Regions.data(),
Regions.data() + Regions.size()).getState();
C.addTransition(state);
}
bool MallocChecker::isReleased(SymbolRef Sym, CheckerContext &C) const {
assert(Sym);
const RefState *RS = C.getState()->get<RegionState>(Sym);
return (RS && RS->isReleased());
}
bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
const Stmt *S) const {
if (isReleased(Sym, C)) {
if (ExplodedNode *N = C.generateSink()) {
if (!BT_UseFree)
BT_UseFree.reset(new BugType("Use-after-free", "Memory Error"));
BugReport *R = new BugReport(*BT_UseFree,
"Use of memory after it is freed",N);
if (S)
R->addRange(S->getSourceRange());
R->markInteresting(Sym);
R->addVisitor(new MallocBugVisitor(Sym));
C.EmitReport(R);
return true;
}
}
return false;
}
// Check if the location is a freed symbolic region.
void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
CheckerContext &C) const {
SymbolRef Sym = l.getLocSymbolInBase();
if (Sym)
checkUseAfterFree(Sym, C, S);
}
//===----------------------------------------------------------------------===//
// Check various ways a symbol can be invalidated.
// TODO: This logic (the next 3 functions) is copied/similar to the
// RetainRelease checker. We might want to factor this out.
//===----------------------------------------------------------------------===//
// Stop tracking symbols when a value escapes as a result of checkBind.
// A value escapes in three possible cases:
// (1) we are binding to something that is not a memory region.
// (2) we are binding to a memregion that does not have stack storage
// (3) we are binding to a memregion with stack storage that the store
// does not understand.
void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S,
CheckerContext &C) const {
// Are we storing to something that causes the value to "escape"?
bool escapes = true;
ProgramStateRef state = C.getState();
if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
escapes = !regionLoc->getRegion()->hasStackStorage();
if (!escapes) {
// To test (3), generate a new state with the binding added. If it is
// the same state, then it escapes (since the store cannot represent
// the binding).
// Do this only if we know that the store is not supposed to generate the
// same state.
SVal StoredVal = state->getSVal(regionLoc->getRegion());
if (StoredVal != val)
escapes = (state == (state->bindLoc(*regionLoc, val)));
}
if (!escapes) {
// Case 4: We do not currently model what happens when a symbol is
// assigned to a struct field, so be conservative here and let the symbol
// go. TODO: This could definitely be improved upon.
escapes = !isa<VarRegion>(regionLoc->getRegion());
}
}
// If our store can represent the binding and we aren't storing to something
// that doesn't have local storage then just return and have the simulation
// state continue as is.
if (!escapes)
return;
// Otherwise, find all symbols referenced by 'val' that we are tracking
// and stop tracking them.
state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
C.addTransition(state);
}
// If a symbolic region is assumed to NULL (or another constant), stop tracking
// it - assuming that allocation failed on this path.
ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
SVal Cond,
bool Assumption) const {
RegionStateTy RS = state->get<RegionState>();
for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
// If the symbol is assumed to NULL or another constant, this will
// return an APSInt*.
if (state->getSymVal(I.getKey()))
state = state->remove<RegionState>(I.getKey());
}
// Realloc returns 0 when reallocation fails, which means that we should
// restore the state of the pointer being reallocated.
ReallocMap RP = state->get<ReallocPairs>();
for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
// If the symbol is assumed to NULL or another constant, this will
// return an APSInt*.
if (state->getSymVal(I.getKey())) {
SymbolRef ReallocSym = I.getData().ReallocatedSym;
const RefState *RS = state->get<RegionState>(ReallocSym);
if (RS) {
if (RS->isReleased() && ! I.getData().IsFreeOnFailure)
state = state->set<RegionState>(ReallocSym,
RefState::getAllocated(RS->getStmt()));
}
state = state->remove<ReallocPairs>(I.getKey());
}
}
return state;
}
// Check if the function is known to us. So, for example, we could
// conservatively assume it can free/reallocate its pointer arguments.
// (We assume that the pointers cannot escape through calls to system
// functions not handled by this checker.)
bool MallocChecker::doesNotFreeMemory(const CallEvent *Call,
ProgramStateRef State) const {
assert(Call);
// For now, assume that any C++ call can free memory.
// TODO: If we want to be more optimistic here, we'll need to make sure that
// regions escape to C++ containers. They seem to do that even now, but for
// mysterious reasons.
if (!(isa<FunctionCall>(Call) || isa<ObjCMethodCall>(Call)))
return false;
// Check Objective-C messages by selector name.
if (const ObjCMethodCall *Msg = dyn_cast<ObjCMethodCall>(Call)) {
// If it's not a framework call, or if it takes a callback, assume it
// can free memory.
if (!Call->isInSystemHeader() || Call->hasNonZeroCallbackArg())
return false;
Selector S = Msg->getSelector();
// Whitelist the ObjC methods which do free memory.
// - Anything containing 'freeWhenDone' param set to 1.
// Ex: dataWithBytesNoCopy:length:freeWhenDone.
for (unsigned i = 1; i < S.getNumArgs(); ++i) {
if (S.getNameForSlot(i).equals("freeWhenDone")) {
if (Call->getArgSVal(i).isConstant(1))
return false;
else
return true;
}
}
// If the first selector ends with NoCopy, assume that the ownership is
// transferred as well.
// Ex: [NSData dataWithBytesNoCopy:bytes length:10];
StringRef FirstSlot = S.getNameForSlot(0);
if (FirstSlot.endswith("NoCopy"))
return false;
// If the first selector starts with addPointer, insertPointer,
// or replacePointer, assume we are dealing with NSPointerArray or similar.
// This is similar to C++ containers (vector); we still might want to check
// that the pointers get freed by following the container itself.
if (FirstSlot.startswith("addPointer") ||
FirstSlot.startswith("insertPointer") ||
FirstSlot.startswith("replacePointer")) {
return false;
}
// Otherwise, assume that the method does not free memory.
// Most framework methods do not free memory.
return true;
}
// At this point the only thing left to handle is straight function calls.
const FunctionDecl *FD = cast<FunctionCall>(Call)->getDecl();
if (!FD)
return false;
ASTContext &ASTC = State->getStateManager().getContext();
// If it's one of the allocation functions we can reason about, we model
// its behavior explicitly.
if (isMemFunction(FD, ASTC))
return true;
// If it's not a system call, assume it frees memory.
if (!Call->isInSystemHeader())
return false;
// White list the system functions whose arguments escape.
const IdentifierInfo *II = FD->getIdentifier();
if (!II)
return false;
StringRef FName = II->getName();
// White list the 'XXXNoCopy' CoreFoundation functions.
// We specifically check these before
if (FName.endswith("NoCopy")) {
// Look for the deallocator argument. We know that the memory ownership
// is not transferred only if the deallocator argument is
// 'kCFAllocatorNull'.
for (unsigned i = 1; i < Call->getNumArgs(); ++i) {
const Expr *ArgE = Call->getArgExpr(i)->IgnoreParenCasts();
if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(ArgE)) {
StringRef DeallocatorName = DE->getFoundDecl()->getName();
if (DeallocatorName == "kCFAllocatorNull")
return true;
}
}
return false;
}
// Associating streams with malloced buffers. The pointer can escape if
// 'closefn' is specified (and if that function does free memory),
// but it will not if closefn is not specified.
// Currently, we do not inspect the 'closefn' function (PR12101).
if (FName == "funopen")
if (Call->getNumArgs() >= 4 && Call->getArgSVal(4).isConstant(0))
return true;
// Do not warn on pointers passed to 'setbuf' when used with std streams,
// these leaks might be intentional when setting the buffer for stdio.
// http://stackoverflow.com/questions/2671151/who-frees-setvbuf-buffer
if (FName == "setbuf" || FName =="setbuffer" ||
FName == "setlinebuf" || FName == "setvbuf") {
if (Call->getNumArgs() >= 1) {
const Expr *ArgE = Call->getArgExpr(0)->IgnoreParenCasts();
if (const DeclRefExpr *ArgDRE = dyn_cast<DeclRefExpr>(ArgE))
if (const VarDecl *D = dyn_cast<VarDecl>(ArgDRE->getDecl()))
if (D->getCanonicalDecl()->getName().find("std") != StringRef::npos)
return false;
}
}
// A bunch of other functions which either take ownership of a pointer or
// wrap the result up in a struct or object, meaning it can be freed later.
// (See RetainCountChecker.) Not all the parameters here are invalidated,
// but the Malloc checker cannot differentiate between them. The right way
// of doing this would be to implement a pointer escapes callback.
if (FName == "CGBitmapContextCreate" ||
FName == "CGBitmapContextCreateWithData" ||
FName == "CVPixelBufferCreateWithBytes" ||
FName == "CVPixelBufferCreateWithPlanarBytes" ||
FName == "OSAtomicEnqueue") {
return false;
}
// Handle cases where we know a buffer's /address/ can escape.
// Note that the above checks handle some special cases where we know that
// even though the address escapes, it's still our responsibility to free the
// buffer.
if (Call->argumentsMayEscape())
return false;
// Otherwise, assume that the function does not free memory.
// Most system calls do not free the memory.
return true;
}
// If the symbol we are tracking is invalidated, but not explicitly (ex: the &p
// escapes, when we are tracking p), do not track the symbol as we cannot reason
// about it anymore.
ProgramStateRef
MallocChecker::checkRegionChanges(ProgramStateRef State,
const StoreManager::InvalidatedSymbols *invalidated,
ArrayRef<const MemRegion *> ExplicitRegions,
ArrayRef<const MemRegion *> Regions,
const CallEvent *Call) const {
if (!invalidated || invalidated->empty())
return State;
llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
// If it's a call which might free or reallocate memory, we assume that all
// regions (explicit and implicit) escaped.
// Otherwise, whitelist explicit pointers; we still can track them.
if (!Call || doesNotFreeMemory(Call, State)) {
for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
E = ExplicitRegions.end(); I != E; ++I) {
if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>())
WhitelistedSymbols.insert(R->getSymbol());
}
}
for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
E = invalidated->end(); I!=E; ++I) {
SymbolRef sym = *I;
if (WhitelistedSymbols.count(sym))
continue;
// The symbol escaped. Note, we assume that if the symbol is released,
// passing it out will result in a use after free. We also keep tracking
// relinquished symbols.
if (const RefState *RS = State->get<RegionState>(sym)) {
if (RS->isAllocated())
State = State->set<RegionState>(sym,
RefState::getEscaped(RS->getStmt()));
}
}
return State;
}
static SymbolRef findFailedReallocSymbol(ProgramStateRef currState,
ProgramStateRef prevState) {
ReallocMap currMap = currState->get<ReallocPairs>();
ReallocMap prevMap = prevState->get<ReallocPairs>();
for (ReallocMap::iterator I = prevMap.begin(), E = prevMap.end();
I != E; ++I) {
SymbolRef sym = I.getKey();
if (!currMap.lookup(sym))
return sym;
}
return NULL;
}
PathDiagnosticPiece *
MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N,
const ExplodedNode *PrevN,
BugReporterContext &BRC,
BugReport &BR) {
ProgramStateRef state = N->getState();
ProgramStateRef statePrev = PrevN->getState();
const RefState *RS = state->get<RegionState>(Sym);
const RefState *RSPrev = statePrev->get<RegionState>(Sym);
if (!RS && !RSPrev)
return 0;
const Stmt *S = 0;
const char *Msg = 0;
StackHintGeneratorForSymbol *StackHint = 0;
// Retrieve the associated statement.
ProgramPoint ProgLoc = N->getLocation();
if (isa<StmtPoint>(ProgLoc))
S = cast<StmtPoint>(ProgLoc).getStmt();
// If an assumption was made on a branch, it should be caught
// here by looking at the state transition.
if (isa<BlockEdge>(ProgLoc)) {
const CFGBlock *srcBlk = cast<BlockEdge>(ProgLoc).getSrc();
S = srcBlk->getTerminator();
}
if (!S)
return 0;
// Find out if this is an interesting point and what is the kind.
if (Mode == Normal) {
if (isAllocated(RS, RSPrev, S)) {
Msg = "Memory is allocated";
StackHint = new StackHintGeneratorForSymbol(Sym,
"Returned allocated memory");
} else if (isReleased(RS, RSPrev, S)) {
Msg = "Memory is released";
StackHint = new StackHintGeneratorForSymbol(Sym,
"Returned released memory");
} else if (isRelinquished(RS, RSPrev, S)) {
Msg = "Memory ownership is transfered";
StackHint = new StackHintGeneratorForSymbol(Sym, "");
} else if (isReallocFailedCheck(RS, RSPrev, S)) {
Mode = ReallocationFailed;
Msg = "Reallocation failed";
StackHint = new StackHintGeneratorForReallocationFailed(Sym,
"Reallocation failed");
if (SymbolRef sym = findFailedReallocSymbol(state, statePrev)) {
// Is it possible to fail two reallocs WITHOUT testing in between?
assert((!FailedReallocSymbol || FailedReallocSymbol == sym) &&
"We only support one failed realloc at a time.");
BR.markInteresting(sym);
FailedReallocSymbol = sym;
}
}
// We are in a special mode if a reallocation failed later in the path.
} else if (Mode == ReallocationFailed) {
assert(FailedReallocSymbol && "No symbol to look for.");
// Is this is the first appearance of the reallocated symbol?
if (!statePrev->get<RegionState>(FailedReallocSymbol)) {
// If we ever hit this assert, that means BugReporter has decided to skip
// node pairs or visit them out of order.
assert(state->get<RegionState>(FailedReallocSymbol) &&
"Missed the reallocation point");
// We're at the reallocation point.
Msg = "Attempt to reallocate memory";
StackHint = new StackHintGeneratorForSymbol(Sym,
"Returned reallocated memory");
FailedReallocSymbol = NULL;
Mode = Normal;
}
}
if (!Msg)
return 0;
assert(StackHint);
// Generate the extra diagnostic.
PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
N->getLocationContext());
return new PathDiagnosticEventPiece(Pos, Msg, true, StackHint);
}
void MallocChecker::printState(raw_ostream &Out, ProgramStateRef State,
const char *NL, const char *Sep) const {
RegionStateTy RS = State->get<RegionState>();
if (!RS.isEmpty())
Out << "Has Malloc data" << NL;
}
#define REGISTER_CHECKER(name) \
void ento::register##name(CheckerManager &mgr) {\
registerCStringCheckerBasic(mgr); \
mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
}
REGISTER_CHECKER(MallocPessimistic)
REGISTER_CHECKER(MallocOptimistic)