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llvm-project/clang/lib/StaticAnalyzer/Checkers/UnixAPIChecker.cpp

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//= UnixAPIChecker.h - Checks preconditions for various Unix APIs --*- C++ -*-//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This defines UnixAPIChecker, which is an assortment of checks on calls
// to various, widely used UNIX/Posix functions.
//
//===----------------------------------------------------------------------===//
#include "ClangSACheckers.h"
#include "clang/Basic/TargetInfo.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/CheckerContext.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/raw_ostream.h"
#include <fcntl.h>
using namespace clang;
using namespace ento;
enum class OpenVariant {
/// The standard open() call:
/// int open(const char *path, int oflag, ...);
Open,
/// The variant taking a directory file descriptor and a relative path:
/// int openat(int fd, const char *path, int oflag, ...);
OpenAt
};
namespace {
class UnixAPIChecker : public Checker< check::PreStmt<CallExpr> > {
mutable std::unique_ptr<BugType> BT_open, BT_pthreadOnce, BT_mallocZero;
mutable Optional<uint64_t> Val_O_CREAT;
public:
void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
void CheckOpen(CheckerContext &C, const CallExpr *CE) const;
void CheckOpenAt(CheckerContext &C, const CallExpr *CE) const;
void CheckPthreadOnce(CheckerContext &C, const CallExpr *CE) const;
void CheckCallocZero(CheckerContext &C, const CallExpr *CE) const;
void CheckMallocZero(CheckerContext &C, const CallExpr *CE) const;
void CheckReallocZero(CheckerContext &C, const CallExpr *CE) const;
void CheckReallocfZero(CheckerContext &C, const CallExpr *CE) const;
void CheckAllocaZero(CheckerContext &C, const CallExpr *CE) const;
void CheckAllocaWithAlignZero(CheckerContext &C, const CallExpr *CE) const;
void CheckVallocZero(CheckerContext &C, const CallExpr *CE) const;
typedef void (UnixAPIChecker::*SubChecker)(CheckerContext &,
const CallExpr *) const;
private:
void CheckOpenVariant(CheckerContext &C,
const CallExpr *CE, OpenVariant Variant) const;
bool ReportZeroByteAllocation(CheckerContext &C,
ProgramStateRef falseState,
const Expr *arg,
const char *fn_name) const;
void BasicAllocationCheck(CheckerContext &C,
const CallExpr *CE,
const unsigned numArgs,
const unsigned sizeArg,
const char *fn) const;
void LazyInitialize(std::unique_ptr<BugType> &BT, const char *name) const {
if (BT)
return;
BT.reset(new BugType(this, name, categories::UnixAPI));
}
void ReportOpenBug(CheckerContext &C,
ProgramStateRef State,
const char *Msg,
SourceRange SR) const;
};
} //end anonymous namespace
//===----------------------------------------------------------------------===//
// "open" (man 2 open)
//===----------------------------------------------------------------------===//
void UnixAPIChecker::ReportOpenBug(CheckerContext &C,
ProgramStateRef State,
const char *Msg,
SourceRange SR) const {
ExplodedNode *N = C.generateErrorNode(State);
if (!N)
return;
LazyInitialize(BT_open, "Improper use of 'open'");
auto Report = llvm::make_unique<BugReport>(*BT_open, Msg, N);
Report->addRange(SR);
C.emitReport(std::move(Report));
}
void UnixAPIChecker::CheckOpen(CheckerContext &C, const CallExpr *CE) const {
CheckOpenVariant(C, CE, OpenVariant::Open);
}
void UnixAPIChecker::CheckOpenAt(CheckerContext &C, const CallExpr *CE) const {
CheckOpenVariant(C, CE, OpenVariant::OpenAt);
}
void UnixAPIChecker::CheckOpenVariant(CheckerContext &C,
const CallExpr *CE,
OpenVariant Variant) const {
// The index of the argument taking the flags open flags (O_RDONLY,
// O_WRONLY, O_CREAT, etc.),
unsigned int FlagsArgIndex;
const char *VariantName;
switch (Variant) {
case OpenVariant::Open:
FlagsArgIndex = 1;
VariantName = "open";
break;
case OpenVariant::OpenAt:
FlagsArgIndex = 2;
VariantName = "openat";
break;
};
// All calls should at least provide arguments up to the 'flags' parameter.
unsigned int MinArgCount = FlagsArgIndex + 1;
// If the flags has O_CREAT set then open/openat() require an additional
// argument specifying the file mode (permission bits) for the created file.
unsigned int CreateModeArgIndex = FlagsArgIndex + 1;
// The create mode argument should be the last argument.
unsigned int MaxArgCount = CreateModeArgIndex + 1;
ProgramStateRef state = C.getState();
if (CE->getNumArgs() < MinArgCount) {
// The frontend should issue a warning for this case, so this is a sanity
// check.
return;
} else if (CE->getNumArgs() == MaxArgCount) {
const Expr *Arg = CE->getArg(CreateModeArgIndex);
QualType QT = Arg->getType();
if (!QT->isIntegerType()) {
SmallString<256> SBuf;
llvm::raw_svector_ostream OS(SBuf);
OS << "The " << CreateModeArgIndex + 1
<< llvm::getOrdinalSuffix(CreateModeArgIndex + 1)
<< " argument to '" << VariantName << "' is not an integer";
ReportOpenBug(C, state,
SBuf.c_str(),
Arg->getSourceRange());
return;
}
} else if (CE->getNumArgs() > MaxArgCount) {
SmallString<256> SBuf;
llvm::raw_svector_ostream OS(SBuf);
OS << "Call to '" << VariantName << "' with more than " << MaxArgCount
<< " arguments";
ReportOpenBug(C, state,
SBuf.c_str(),
CE->getArg(MaxArgCount)->getSourceRange());
return;
}
// The definition of O_CREAT is platform specific. We need a better way
// of querying this information from the checking environment.
if (!Val_O_CREAT.hasValue()) {
if (C.getASTContext().getTargetInfo().getTriple().getVendor()
== llvm::Triple::Apple)
Val_O_CREAT = 0x0200;
else {
// FIXME: We need a more general way of getting the O_CREAT value.
// We could possibly grovel through the preprocessor state, but
// that would require passing the Preprocessor object to the ExprEngine.
// See also: MallocChecker.cpp / M_ZERO.
return;
}
}
// Now check if oflags has O_CREAT set.
const Expr *oflagsEx = CE->getArg(FlagsArgIndex);
const SVal V = state->getSVal(oflagsEx, C.getLocationContext());
if (!V.getAs<NonLoc>()) {
// The case where 'V' can be a location can only be due to a bad header,
// so in this case bail out.
return;
}
NonLoc oflags = V.castAs<NonLoc>();
NonLoc ocreateFlag = C.getSValBuilder()
.makeIntVal(Val_O_CREAT.getValue(), oflagsEx->getType()).castAs<NonLoc>();
SVal maskedFlagsUC = C.getSValBuilder().evalBinOpNN(state, BO_And,
oflags, ocreateFlag,
oflagsEx->getType());
if (maskedFlagsUC.isUnknownOrUndef())
return;
DefinedSVal maskedFlags = maskedFlagsUC.castAs<DefinedSVal>();
// Check if maskedFlags is non-zero.
ProgramStateRef trueState, falseState;
std::tie(trueState, falseState) = state->assume(maskedFlags);
// Only emit an error if the value of 'maskedFlags' is properly
// constrained;
if (!(trueState && !falseState))
return;
if (CE->getNumArgs() < MaxArgCount) {
SmallString<256> SBuf;
llvm::raw_svector_ostream OS(SBuf);
OS << "Call to '" << VariantName << "' requires a "
<< CreateModeArgIndex + 1
<< llvm::getOrdinalSuffix(CreateModeArgIndex + 1)
<< " argument when the 'O_CREAT' flag is set";
ReportOpenBug(C, trueState,
SBuf.c_str(),
oflagsEx->getSourceRange());
}
}
//===----------------------------------------------------------------------===//
// pthread_once
//===----------------------------------------------------------------------===//
void UnixAPIChecker::CheckPthreadOnce(CheckerContext &C,
const CallExpr *CE) const {
// This is similar to 'CheckDispatchOnce' in the MacOSXAPIChecker.
// They can possibly be refactored.
if (CE->getNumArgs() < 1)
return;
// Check if the first argument is stack allocated. If so, issue a warning
// because that's likely to be bad news.
ProgramStateRef state = C.getState();
const MemRegion *R =
state->getSVal(CE->getArg(0), C.getLocationContext()).getAsRegion();
if (!R || !isa<StackSpaceRegion>(R->getMemorySpace()))
return;
ExplodedNode *N = C.generateErrorNode(state);
if (!N)
return;
SmallString<256> S;
llvm::raw_svector_ostream os(S);
os << "Call to 'pthread_once' uses";
if (const VarRegion *VR = dyn_cast<VarRegion>(R))
os << " the local variable '" << VR->getDecl()->getName() << '\'';
else
os << " stack allocated memory";
os << " for the \"control\" value. Using such transient memory for "
"the control value is potentially dangerous.";
if (isa<VarRegion>(R) && isa<StackLocalsSpaceRegion>(R->getMemorySpace()))
os << " Perhaps you intended to declare the variable as 'static'?";
LazyInitialize(BT_pthreadOnce, "Improper use of 'pthread_once'");
auto report = llvm::make_unique<BugReport>(*BT_pthreadOnce, os.str(), N);
report->addRange(CE->getArg(0)->getSourceRange());
C.emitReport(std::move(report));
}
//===----------------------------------------------------------------------===//
// "calloc", "malloc", "realloc", "reallocf", "alloca" and "valloc"
// with allocation size 0
//===----------------------------------------------------------------------===//
// FIXME: Eventually these should be rolled into the MallocChecker, but right now
// they're more basic and valuable for widespread use.
// Returns true if we try to do a zero byte allocation, false otherwise.
// Fills in trueState and falseState.
static bool IsZeroByteAllocation(ProgramStateRef state,
const SVal argVal,
ProgramStateRef *trueState,
ProgramStateRef *falseState) {
std::tie(*trueState, *falseState) =
state->assume(argVal.castAs<DefinedSVal>());
return (*falseState && !*trueState);
}
// Generates an error report, indicating that the function whose name is given
// will perform a zero byte allocation.
// Returns false if an error occurred, true otherwise.
bool UnixAPIChecker::ReportZeroByteAllocation(CheckerContext &C,
ProgramStateRef falseState,
const Expr *arg,
const char *fn_name) const {
ExplodedNode *N = C.generateErrorNode(falseState);
if (!N)
return false;
LazyInitialize(BT_mallocZero,
"Undefined allocation of 0 bytes (CERT MEM04-C; CWE-131)");
SmallString<256> S;
llvm::raw_svector_ostream os(S);
os << "Call to '" << fn_name << "' has an allocation size of 0 bytes";
auto report = llvm::make_unique<BugReport>(*BT_mallocZero, os.str(), N);
report->addRange(arg->getSourceRange());
bugreporter::trackNullOrUndefValue(N, arg, *report);
C.emitReport(std::move(report));
return true;
}
// Does a basic check for 0-sized allocations suitable for most of the below
// functions (modulo "calloc")
void UnixAPIChecker::BasicAllocationCheck(CheckerContext &C,
const CallExpr *CE,
const unsigned numArgs,
const unsigned sizeArg,
const char *fn) const {
// Sanity check for the correct number of arguments
if (CE->getNumArgs() != numArgs)
return;
// Check if the allocation size is 0.
ProgramStateRef state = C.getState();
ProgramStateRef trueState = nullptr, falseState = nullptr;
const Expr *arg = CE->getArg(sizeArg);
SVal argVal = state->getSVal(arg, C.getLocationContext());
if (argVal.isUnknownOrUndef())
return;
// Is the value perfectly constrained to zero?
if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {
(void) ReportZeroByteAllocation(C, falseState, arg, fn);
return;
}
// Assume the value is non-zero going forward.
assert(trueState);
if (trueState != state)
C.addTransition(trueState);
}
void UnixAPIChecker::CheckCallocZero(CheckerContext &C,
const CallExpr *CE) const {
unsigned int nArgs = CE->getNumArgs();
if (nArgs != 2)
return;
ProgramStateRef state = C.getState();
ProgramStateRef trueState = nullptr, falseState = nullptr;
unsigned int i;
for (i = 0; i < nArgs; i++) {
const Expr *arg = CE->getArg(i);
SVal argVal = state->getSVal(arg, C.getLocationContext());
if (argVal.isUnknownOrUndef()) {
if (i == 0)
continue;
else
return;
}
if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {
if (ReportZeroByteAllocation(C, falseState, arg, "calloc"))
return;
else if (i == 0)
continue;
else
return;
}
}
// Assume the value is non-zero going forward.
assert(trueState);
if (trueState != state)
C.addTransition(trueState);
}
void UnixAPIChecker::CheckMallocZero(CheckerContext &C,
const CallExpr *CE) const {
BasicAllocationCheck(C, CE, 1, 0, "malloc");
}
void UnixAPIChecker::CheckReallocZero(CheckerContext &C,
const CallExpr *CE) const {
BasicAllocationCheck(C, CE, 2, 1, "realloc");
}
void UnixAPIChecker::CheckReallocfZero(CheckerContext &C,
const CallExpr *CE) const {
BasicAllocationCheck(C, CE, 2, 1, "reallocf");
}
void UnixAPIChecker::CheckAllocaZero(CheckerContext &C,
const CallExpr *CE) const {
BasicAllocationCheck(C, CE, 1, 0, "alloca");
}
void UnixAPIChecker::CheckAllocaWithAlignZero(CheckerContext &C,
const CallExpr *CE) const {
BasicAllocationCheck(C, CE, 2, 0, "__builtin_alloca_with_align");
}
void UnixAPIChecker::CheckVallocZero(CheckerContext &C,
const CallExpr *CE) const {
BasicAllocationCheck(C, CE, 1, 0, "valloc");
}
//===----------------------------------------------------------------------===//
// Central dispatch function.
//===----------------------------------------------------------------------===//
void UnixAPIChecker::checkPreStmt(const CallExpr *CE,
CheckerContext &C) const {
const FunctionDecl *FD = C.getCalleeDecl(CE);
if (!FD || FD->getKind() != Decl::Function)
return;
// Don't treat functions in namespaces with the same name a Unix function
// as a call to the Unix function.
const DeclContext *NamespaceCtx = FD->getEnclosingNamespaceContext();
if (NamespaceCtx && isa<NamespaceDecl>(NamespaceCtx))
return;
StringRef FName = C.getCalleeName(FD);
if (FName.empty())
return;
SubChecker SC =
llvm::StringSwitch<SubChecker>(FName)
.Case("open", &UnixAPIChecker::CheckOpen)
.Case("openat", &UnixAPIChecker::CheckOpenAt)
.Case("pthread_once", &UnixAPIChecker::CheckPthreadOnce)
.Case("calloc", &UnixAPIChecker::CheckCallocZero)
.Case("malloc", &UnixAPIChecker::CheckMallocZero)
.Case("realloc", &UnixAPIChecker::CheckReallocZero)
.Case("reallocf", &UnixAPIChecker::CheckReallocfZero)
.Cases("alloca", "__builtin_alloca", &UnixAPIChecker::CheckAllocaZero)
.Case("__builtin_alloca_with_align",
&UnixAPIChecker::CheckAllocaWithAlignZero)
.Case("valloc", &UnixAPIChecker::CheckVallocZero)
.Default(nullptr);
if (SC)
(this->*SC)(C, CE);
}
//===----------------------------------------------------------------------===//
// Registration.
//===----------------------------------------------------------------------===//
void ento::registerUnixAPIChecker(CheckerManager &mgr) {
mgr.registerChecker<UnixAPIChecker>();
}
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