//=== 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/AST/Attr.h"
#include "clang/Basic/SourceManager.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
#include "llvm/ADT/ImmutableMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.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,
// 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 getRelinquished(const Stmt *s) {
return RefState(Relinquished, s);
}
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.AddInteger(K);
ID.AddPointer(S);
}
void dump(raw_ostream &OS) const {
static const char *Table[] = {
"Allocated",
"Released",
"Relinquished"
};
OS << Table[(unsigned) K];
}
LLVM_ATTRIBUTE_USED void dump() const {
dump(llvm::errs());
}
};
enum ReallocPairKind {
RPToBeFreedAfterFailure,
// The symbol has been freed when reallocation failed.
RPIsFreeOnFailure,
// The symbol does not need to be freed after reallocation fails.
RPDoNotTrackAfterFailure
};
/// \class ReallocPair
/// \brief Stores information about the symbol being reallocated by a call to
/// 'realloc' to allow modeling failed reallocation later in the path.
struct ReallocPair {
// \brief The symbol which realloc reallocated.
SymbolRef ReallocatedSym;
ReallocPairKind Kind;
ReallocPair(SymbolRef S, ReallocPairKind K) :
ReallocatedSym(S), Kind(K) {}
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.AddInteger(Kind);
ID.AddPointer(ReallocatedSym);
}
bool operator==(const ReallocPair &X) const {
return ReallocatedSym == X.ReallocatedSym &&
Kind == X.Kind;
}
};
typedef std::pair<const ExplodedNode*, const MemRegion*> LeakInfo;
class MallocChecker : public Checker<check::DeadSymbols,
check::PointerEscape,
check::PreStmt<ReturnStmt>,
check::PreStmt<CallExpr>,
check::PostStmt<CallExpr>,
check::PostStmt<BlockExpr>,
check::PostObjCMessage,
check::Location,
eval::Assume>
{
mutable OwningPtr<BugType> BT_DoubleFree;
mutable OwningPtr<BugType> BT_Leak;
mutable OwningPtr<BugType> BT_UseFree;
mutable OwningPtr<BugType> BT_BadFree;
mutable OwningPtr<BugType> BT_OffsetFree;
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 checkPostObjCMessage(const ObjCMethodCall &Call, CheckerContext &C) const;
void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
void checkDeadSymbols(SymbolReaper &SymReaper, 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;
ProgramStateRef checkPointerEscape(ProgramStateRef State,
const InvalidatedSymbols &Escaped,
const CallEvent *Call,
PointerEscapeKind Kind) const;
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,
bool &ReleasedAllocated,
bool ReturnsNullOnFailure = false) const;
ProgramStateRef FreeMemAux(CheckerContext &C, const Expr *Arg,
const Expr *ParentExpr,
ProgramStateRef State,
bool Hold,
bool &ReleasedAllocated,
bool ReturnsNullOnFailure = false) 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 checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
const Stmt *S = 0) const;
/// Check if the function is known not to free memory, or if it is
/// "interesting" and should be modeled explicitly.
///
/// We assume that pointers do not escape through calls to system functions
/// not handled by this checker.
bool doesNotFreeMemOrInteresting(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;
void ReportBadDealloc(CheckerContext &C, SourceRange Range,
const Expr *DeallocExpr, const RefState *RS) const;
void ReportOffsetFree(CheckerContext &C, SVal ArgVal, SourceRange Range)const;
void ReportUseAfterFree(CheckerContext &C, SourceRange Range,
SymbolRef Sym) const;
void ReportDoubleFree(CheckerContext &C, SourceRange Range, bool Released,
SymbolRef Sym, SymbolRef PrevSym) 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) {
// Printed parameters start at 1, not 0.
++ArgIndex;
SmallString<200> buf;
llvm::raw_svector_ostream os(buf);
os << "Reallocation of " << ArgIndex << llvm::getOrdinalSuffix(ArgIndex)
<< " parameter failed";
return os.str();
}
virtual std::string getMessageForReturn(const CallExpr *CallExpr) {
return "Reallocation of returned value failed";
}
};
};
};
} // end anonymous namespace
REGISTER_MAP_WITH_PROGRAMSTATE(RegionState, SymbolRef, RefState)
REGISTER_MAP_WITH_PROGRAMSTATE(ReallocPairs, SymbolRef, ReallocPair)
// A map from the freed symbol to the symbol representing the return value of
// the free function.
REGISTER_MAP_WITH_PROGRAMSTATE(FreeReturnValue, SymbolRef, SymbolRef)
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;
if (FD->getKind() == Decl::Function) {
IdentifierInfo *FunI = FD->getIdentifier();
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;
if (FD->getKind() == Decl::Function) {
IdentifierInfo *FunI = FD->getIdentifier();
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 {
if (C.wasInlined)
return;
const FunctionDecl *FD = C.getCalleeDecl(CE);
if (!FD)
return;
ProgramStateRef State = C.getState();
bool ReleasedAllocatedMemory = false;
if (FD->getKind() == Decl::Function) {
initIdentifierInfo(C.getASTContext());
IdentifierInfo *FunI = FD->getIdentifier();
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, State, 0, false, ReleasedAllocatedMemory);
} else if (FunI == II_strdup) {
State = MallocUpdateRefState(C, CE, State);
} else if (FunI == II_strndup) {
State = MallocUpdateRefState(C, CE, State);
}
}
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 isKnownDeallocObjCMethodName(const ObjCMethodCall &Call) {
// If the first selector piece is one of the names below, assume that the
// object takes ownership of the memory, promising to eventually deallocate it
// with free().
// Ex: [NSData dataWithBytesNoCopy:bytes length:10];
// (...unless a 'freeWhenDone' parameter is false, but that's checked later.)
StringRef FirstSlot = Call.getSelector().getNameForSlot(0);
if (FirstSlot == "dataWithBytesNoCopy" ||
FirstSlot == "initWithBytesNoCopy" ||
FirstSlot == "initWithCharactersNoCopy")
return true;
return false;
}
static Optional<bool> getFreeWhenDoneArg(const ObjCMethodCall &Call) {
Selector S = Call.getSelector();
// FIXME: We should not rely on fully-constrained symbols being folded.
for (unsigned i = 1; i < S.getNumArgs(); ++i)
if (S.getNameForSlot(i).equals("freeWhenDone"))
return !Call.getArgSVal(i).isZeroConstant();
return None;
}
void MallocChecker::checkPostObjCMessage(const ObjCMethodCall &Call,
CheckerContext &C) const {
if (C.wasInlined)
return;
if (!isKnownDeallocObjCMethodName(Call))
return;
if (Optional<bool> FreeWhenDone = getFreeWhenDoneArg(Call))
if (!*FreeWhenDone)
return;
bool ReleasedAllocatedMemory;
ProgramStateRef State = FreeMemAux(C, Call.getArgExpr(0),
Call.getOriginExpr(), C.getState(),
/*Hold=*/true, ReleasedAllocatedMemory,
/*RetNullOnFailure=*/true);
C.addTransition(State);
}
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.blockCount();
SValBuilder &svalBuilder = C.getSValBuilder();
const LocationContext *LCtx = C.getPredecessor()->getLocationContext();
DefinedSVal RetVal = svalBuilder.getConjuredHeapSymbolVal(CE, LCtx, Count)
.castAs<DefinedSVal>();
state = state->BindExpr(CE, C.getLocationContext(), RetVal);
// We expect the malloc functions to return a pointer.
if (!RetVal.getAs<Loc>())
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 (Optional<DefinedOrUnknownSVal> DefinedSize =
Size.getAs<DefinedOrUnknownSVal>()) {
SValBuilder &svalBuilder = C.getSValBuilder();
DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
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 (!retVal.getAs<Loc>())
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();
bool ReleasedAllocated = false;
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,
ReleasedAllocated);
if (StateI)
State = StateI;
}
return State;
}
ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
const CallExpr *CE,
ProgramStateRef state,
unsigned Num,
bool Hold,
bool &ReleasedAllocated,
bool ReturnsNullOnFailure) const {
if (CE->getNumArgs() < (Num + 1))
return 0;
return FreeMemAux(C, CE->getArg(Num), CE, state, Hold,
ReleasedAllocated, ReturnsNullOnFailure);
}
/// Checks if the previous call to free on the given symbol failed - if free
/// failed, returns true. Also, returns the corresponding return value symbol.
static bool didPreviousFreeFail(ProgramStateRef State,
SymbolRef Sym, SymbolRef &RetStatusSymbol) {
const SymbolRef *Ret = State->get<FreeReturnValue>(Sym);
if (Ret) {
assert(*Ret && "We should not store the null return symbol");
ConstraintManager &CMgr = State->getConstraintManager();
ConditionTruthVal FreeFailed = CMgr.isNull(State, *Ret);
RetStatusSymbol = *Ret;
return FreeFailed.isConstrainedTrue();
}
return false;
}
ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
const Expr *ArgExpr,
const Expr *ParentExpr,
ProgramStateRef State,
bool Hold,
bool &ReleasedAllocated,
bool ReturnsNullOnFailure) const {
SVal ArgVal = State->getSVal(ArgExpr, C.getLocationContext());
if (!ArgVal.getAs<DefinedOrUnknownSVal>())
return 0;
DefinedOrUnknownSVal location = ArgVal.castAs<DefinedOrUnknownSVal>();
// Check for null dereferences.
if (!location.getAs<Loc>())
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, globals, and memory returned by alloca()
// 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 *SrBase = dyn_cast<SymbolicRegion>(R->getBaseRegion());
// Various cases could lead to non-symbol values here.
// For now, ignore them.
if (!SrBase)
return 0;
SymbolRef SymBase = SrBase->getSymbol();
const RefState *RsBase = State->get<RegionState>(SymBase);
SymbolRef PreviousRetStatusSymbol = 0;
// Check double free.
if (RsBase &&
(RsBase->isReleased() || RsBase->isRelinquished()) &&
!didPreviousFreeFail(State, SymBase, PreviousRetStatusSymbol)) {
ReportDoubleFree(C, ParentExpr->getSourceRange(), RsBase->isReleased(),
SymBase, PreviousRetStatusSymbol);
return 0;
}
// Check if the memory location being freed is the actual location
// allocated, or an offset.
RegionOffset Offset = R->getAsOffset();
if (RsBase && RsBase->isAllocated() &&
Offset.isValid() &&
!Offset.hasSymbolicOffset() &&
Offset.getOffset() != 0) {
ReportOffsetFree(C, ArgVal, ArgExpr->getSourceRange());
return 0;
}
ReleasedAllocated = (RsBase != 0);
// Clean out the info on previous call to free return info.
State = State->remove<FreeReturnValue>(SymBase);
// Keep track of the return value. If it is NULL, we will know that free
// failed.
if (ReturnsNullOnFailure) {
SVal RetVal = C.getSVal(ParentExpr);
SymbolRef RetStatusSymbol = RetVal.getAsSymbol();
if (RetStatusSymbol) {
C.getSymbolManager().addSymbolDependency(SymBase, RetStatusSymbol);
State = State->set<FreeReturnValue>(SymBase, RetStatusSymbol);
}
}
// Normal free.
if (Hold) {
return State->set<RegionState>(SymBase,
RefState::getRelinquished(ParentExpr));
}
return State->set<RegionState>(SymBase, RefState::getReleased(ParentExpr));
}
bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
if (Optional<nonloc::ConcreteInt> IntVal = V.getAs<nonloc::ConcreteInt>())
os << "an integer (" << IntVal->getValue() << ")";
else if (Optional<loc::ConcreteInt> ConstAddr = V.getAs<loc::ConcreteInt>())
os << "a constant address (" << ConstAddr->getValue() << ")";
else if (Optional<loc::GotoLabel> Label = V.getAs<loc::GotoLabel>())
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 NamedDecl *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);
}
}
void MallocChecker::ReportOffsetFree(CheckerContext &C, SVal ArgVal,
SourceRange Range) const {
ExplodedNode *N = C.generateSink();
if (N == NULL)
return;
if (!BT_OffsetFree)
BT_OffsetFree.reset(new BugType("Offset free", "Memory Error"));
SmallString<100> buf;
llvm::raw_svector_ostream os(buf);
const MemRegion *MR = ArgVal.getAsRegion();
assert(MR && "Only MemRegion based symbols can have offset free errors");
RegionOffset Offset = MR->getAsOffset();
assert((Offset.isValid() &&
!Offset.hasSymbolicOffset() &&
Offset.getOffset() != 0) &&
"Only symbols with a valid offset can have offset free errors");
int offsetBytes = Offset.getOffset() / C.getASTContext().getCharWidth();
os << "Argument to free() is offset by "
<< offsetBytes
<< " "
<< ((abs(offsetBytes) > 1) ? "bytes" : "byte")
<< " from the start of memory allocated by malloc()";
BugReport *R = new BugReport(*BT_OffsetFree, os.str(), N);
R->markInteresting(MR->getBaseRegion());
R->addRange(Range);
C.emitReport(R);
}
void MallocChecker::ReportUseAfterFree(CheckerContext &C, SourceRange Range,
SymbolRef Sym) const {
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);
R->markInteresting(Sym);
R->addRange(Range);
R->addVisitor(new MallocBugVisitor(Sym));
C.emitReport(R);
}
}
void MallocChecker::ReportDoubleFree(CheckerContext &C, SourceRange Range,
bool Released, SymbolRef Sym,
SymbolRef PrevSym) const {
if (ExplodedNode *N = C.generateSink()) {
if (!BT_DoubleFree)
BT_DoubleFree.reset(new BugType("Double free", "Memory Error"));
BugReport *R = new BugReport(*BT_DoubleFree,
(Released ? "Attempt to free released memory"
: "Attempt to free non-owned memory"),
N);
R->addRange(Range);
R->markInteresting(Sym);
if (PrevSym)
R->markInteresting(PrevSym);
R->addVisitor(new MallocBugVisitor(Sym));
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 (!Arg0Val.getAs<DefinedOrUnknownSVal>())
return 0;
DefinedOrUnknownSVal arg0Val = Arg0Val.castAs<DefinedOrUnknownSVal>();
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 (!Arg1ValG.getAs<DefinedOrUnknownSVal>())
return 0;
DefinedOrUnknownSVal Arg1Val = Arg1ValG.castAs<DefinedOrUnknownSVal>();
// 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;
bool ReleasedAllocated = false;
// If the size is 0, free the memory.
if (SizeIsZero)
if (ProgramStateRef stateFree = FreeMemAux(C, CE, StateSizeIsZero, 0,
false, ReleasedAllocated)){
// 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. We just free the input pointer and do not add
// any constrains on the output pointer.
return stateFree;
}
// Default behavior.
if (ProgramStateRef stateFree =
FreeMemAux(C, CE, state, 0, false, ReleasedAllocated)) {
ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1),
UnknownVal(), stateFree);
if (!stateRealloc)
return 0;
ReallocPairKind Kind = RPToBeFreedAfterFailure;
if (FreesOnFail)
Kind = RPIsFreeOnFailure;
else if (!ReleasedAllocated)
Kind = RPDoNotTrackAfterFailure;
// Record the info about the reallocated symbol so that we could properly
// process failed reallocation.
stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr,
ReallocPair(FromPtr, Kind));
// The reallocated symbol should stay alive for as long as the new symbol.
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());
}
return LeakInfo(AllocNode, 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 ExplodedNode *AllocNode = 0;
const MemRegion *Region = 0;
llvm::tie(AllocNode, Region) = getAllocationSite(N, Sym, C);
ProgramPoint P = AllocNode->getLocation();
const Stmt *AllocationStmt = 0;
if (Optional<CallExitEnd> Exit = P.getAs<CallExitEnd>())
AllocationStmt = Exit->getCalleeContext()->getCallSite();
else if (Optional<StmtPoint> SP = P.getAs<StmtPoint>())
AllocationStmt = SP->getStmt();
if (AllocationStmt)
LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocationStmt,
C.getSourceManager(),
AllocNode->getLocationContext());
SmallString<200> buf;
llvm::raw_svector_ostream os(buf);
os << "Memory is never released; potential leak";
if (Region && Region->canPrintPretty()) {
os << " of memory pointed to by '";
Region->printPretty(os);
os << '\'';
}
BugReport *R = new BugReport(*BT_Leak, os.str(), N,
LocUsedForUniqueing,
AllocNode->getLocationContext()->getDecl());
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>();
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())
Errors.push_back(I->first);
// Remove the dead symbol from the map.
RS = F.remove(RS, I->first);
}
}
// Cleanup the Realloc Pairs Map.
ReallocPairsTy RP = state->get<ReallocPairs>();
for (ReallocPairsTy::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);
}
}
// Cleanup the FreeReturnValue Map.
FreeReturnValueTy FR = state->get<FreeReturnValue>();
for (FreeReturnValueTy::iterator I = FR.begin(), E = FR.end(); I != E; ++I) {
if (SymReaper.isDead(I->first) ||
SymReaper.isDead(I->second)) {
state = state->remove<FreeReturnValue>(I->first);
}
}
// Generate leak node.
ExplodedNode *N = C.getPredecessor();
if (!Errors.empty()) {
static SimpleProgramPointTag Tag("MallocChecker : DeadSymbolsLeak");
N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
for (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::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 = C.getSVal(A).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.
ProgramStateRef State = C.getState();
SVal RetVal = State->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();
// Check if we are returning freed memory.
if (Sym)
checkUseAfterFree(Sym, C, E);
}
// 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.getCapturedRegion();
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)) {
ReportUseAfterFree(C, S->getSourceRange(), Sym);
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);
}
// 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 be NULL, remove it from consideration.
ConstraintManager &CMgr = state->getConstraintManager();
ConditionTruthVal AllocFailed = CMgr.isNull(state, I.getKey());
if (AllocFailed.isConstrainedTrue())
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.
ReallocPairsTy RP = state->get<ReallocPairs>();
for (ReallocPairsTy::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
// If the symbol is assumed to be NULL, remove it from consideration.
ConstraintManager &CMgr = state->getConstraintManager();
ConditionTruthVal AllocFailed = CMgr.isNull(state, I.getKey());
if (!AllocFailed.isConstrainedTrue())
continue;
SymbolRef ReallocSym = I.getData().ReallocatedSym;
if (const RefState *RS = state->get<RegionState>(ReallocSym)) {
if (RS->isReleased()) {
if (I.getData().Kind == RPToBeFreedAfterFailure)
state = state->set<RegionState>(ReallocSym,
RefState::getAllocated(RS->getStmt()));
else if (I.getData().Kind == RPDoNotTrackAfterFailure)
state = state->remove<RegionState>(ReallocSym);
else
assert(I.getData().Kind == RPIsFreeOnFailure);
}
}
state = state->remove<ReallocPairs>(I.getKey());
}
return state;
}
bool MallocChecker::doesNotFreeMemOrInteresting(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;
// If it's a method we know about, handle it explicitly post-call.
// This should happen before the "freeWhenDone" check below.
if (isKnownDeallocObjCMethodName(*Msg))
return true;
// If there's a "freeWhenDone" parameter, but the method isn't one we know
// about, we can't be sure that the object will use free() to deallocate the
// memory, so we can't model it explicitly. The best we can do is use it to
// decide whether the pointer escapes.
if (Optional<bool> FreeWhenDone = getFreeWhenDoneArg(*Msg))
return !*FreeWhenDone;
// If the first selector piece ends with "NoCopy", and there is no
// "freeWhenDone" parameter set to zero, we know ownership is being
// transferred. Again, though, we can't be sure that the object will use
// free() to deallocate the memory, so we can't model it explicitly.
StringRef FirstSlot = Msg->getSelector().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;
}
ProgramStateRef MallocChecker::checkPointerEscape(ProgramStateRef State,
const InvalidatedSymbols &Escaped,
const CallEvent *Call,
PointerEscapeKind Kind) const {
// If we know that the call does not free memory, or we want to process the
// call later, keep tracking the top level arguments.
if ((Kind == PSK_DirectEscapeOnCall ||
Kind == PSK_IndirectEscapeOnCall) &&
doesNotFreeMemOrInteresting(Call, State)) {
return State;
}
for (InvalidatedSymbols::const_iterator I = Escaped.begin(),
E = Escaped.end();
I != E; ++I) {
SymbolRef sym = *I;
if (const RefState *RS = State->get<RegionState>(sym)) {
if (RS->isAllocated())
State = State->remove<RegionState>(sym);
}
}
return State;
}
static SymbolRef findFailedReallocSymbol(ProgramStateRef currState,
ProgramStateRef prevState) {
ReallocPairsTy currMap = currState->get<ReallocPairs>();
ReallocPairsTy prevMap = prevState->get<ReallocPairs>();
for (ReallocPairsTy::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)
return 0;
const Stmt *S = 0;
const char *Msg = 0;
StackHintGeneratorForSymbol *StackHint = 0;
// Retrieve the associated statement.
ProgramPoint ProgLoc = N->getLocation();
if (Optional<StmtPoint> SP = ProgLoc.getAs<StmtPoint>()) {
S = SP->getStmt();
} else if (Optional<CallExitEnd> Exit = ProgLoc.getAs<CallExitEnd>()) {
S = Exit->getCalleeContext()->getCallSite();
} else if (Optional<BlockEdge> Edge = ProgLoc.getAs<BlockEdge>()) {
// If an assumption was made on a branch, it should be caught
// here by looking at the state transition.
S = Edge->getSrc()->getTerminator();
}
if (!S)
return 0;
// FIXME: We will eventually need to handle non-statement-based events
// (__attribute__((cleanup))).
// 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)) {
// 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 << Sep << "MallocChecker:" << NL;
for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
I.getKey()->dumpToStream(Out);
Out << " : ";
I.getData().dump(Out);
Out << 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)