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diff --git a/clang/lib/StaticAnalyzer/Checkers/MIGChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/MIGChecker.cpp
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+++ b/clang/lib/StaticAnalyzer/Checkers/MIGChecker.cpp
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+//== MIGChecker.cpp - MIG calling convention checker ------------*- C++ -*--==//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines MIGChecker, a Mach Interface Generator calling convention
+// checker. Namely, in MIG callback implementation the following rules apply:
+// - When a server routine returns an error code that represents success, it
+//   must take ownership of resources passed to it (and eventually release
+//   them).
+// - Additionally, when returning success, all out-parameters must be
+//   initialized.
+// - When it returns any other error code, it must not take ownership,
+//   because the message and its out-of-line parameters will be destroyed
+//   by the client that called the function.
+// For now we only check the last rule, as its violations lead to dangerous
+// use-after-free exploits.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/AnyCall.h"
+#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.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"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class MIGChecker : public Checker<check::PostCall, check::PreStmt<ReturnStmt>,
+                                  check::EndFunction> {
+  BugType BT{this, "Use-after-free (MIG calling convention violation)",
+             categories::MemoryError};
+
+  // The checker knows that an out-of-line object is deallocated if it is
+  // passed as an argument to one of these functions. If this object is
+  // additionally an argument of a MIG routine, the checker keeps track of that
+  // information and issues a warning when an error is returned from the
+  // respective routine.
+  std::vector<std::pair<CallDescription, unsigned>> Deallocators = {
+#define CALL(required_args, deallocated_arg, ...)                              \
+  {{{__VA_ARGS__}, required_args}, deallocated_arg}
+      // E.g., if the checker sees a C function 'vm_deallocate' that is
+      // defined on class 'IOUserClient' that has exactly 3 parameters, it knows
+      // that argument #1 (starting from 0, i.e. the second argument) is going
+      // to be consumed in the sense of the MIG consume-on-success convention.
+      CALL(3, 1, "vm_deallocate"),
+      CALL(3, 1, "mach_vm_deallocate"),
+      CALL(2, 0, "mig_deallocate"),
+      CALL(2, 1, "mach_port_deallocate"),
+      CALL(1, 0, "device_deallocate"),
+      CALL(1, 0, "iokit_remove_connect_reference"),
+      CALL(1, 0, "iokit_remove_reference"),
+      CALL(1, 0, "iokit_release_port"),
+      CALL(1, 0, "ipc_port_release"),
+      CALL(1, 0, "ipc_port_release_sonce"),
+      CALL(1, 0, "ipc_voucher_attr_control_release"),
+      CALL(1, 0, "ipc_voucher_release"),
+      CALL(1, 0, "lock_set_dereference"),
+      CALL(1, 0, "memory_object_control_deallocate"),
+      CALL(1, 0, "pset_deallocate"),
+      CALL(1, 0, "semaphore_dereference"),
+      CALL(1, 0, "space_deallocate"),
+      CALL(1, 0, "space_inspect_deallocate"),
+      CALL(1, 0, "task_deallocate"),
+      CALL(1, 0, "task_inspect_deallocate"),
+      CALL(1, 0, "task_name_deallocate"),
+      CALL(1, 0, "thread_deallocate"),
+      CALL(1, 0, "thread_inspect_deallocate"),
+      CALL(1, 0, "upl_deallocate"),
+      CALL(1, 0, "vm_map_deallocate"),
+      // E.g., if the checker sees a method 'releaseAsyncReference64()' that is
+      // defined on class 'IOUserClient' that takes exactly 1 argument, it knows
+      // that the argument is going to be consumed in the sense of the MIG
+      // consume-on-success convention.
+      CALL(1, 0, "IOUserClient", "releaseAsyncReference64"),
+      CALL(1, 0, "IOUserClient", "releaseNotificationPort"),
+#undef CALL
+  };
+
+  CallDescription OsRefRetain{"os_ref_retain", 1};
+
+  void checkReturnAux(const ReturnStmt *RS, CheckerContext &C) const;
+
+public:
+  void checkPostCall(const CallEvent &Call, CheckerContext &C) const;
+
+  // HACK: We're making two attempts to find the bug: checkEndFunction
+  // should normally be enough but it fails when the return value is a literal
+  // that never gets put into the Environment and ends of function with multiple
+  // returns get agglutinated across returns, preventing us from obtaining
+  // the return value. The problem is similar to https://reviews.llvm.org/D25326
+  // but now we step into it in the top-level function.
+  void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const {
+    checkReturnAux(RS, C);
+  }
+  void checkEndFunction(const ReturnStmt *RS, CheckerContext &C) const {
+    checkReturnAux(RS, C);
+  }
+
+};
+} // end anonymous namespace
+
+// A flag that says that the programmer has called a MIG destructor
+// for at least one parameter.
+REGISTER_TRAIT_WITH_PROGRAMSTATE(ReleasedParameter, bool)
+// A set of parameters for which the check is suppressed because
+// reference counting is being performed.
+REGISTER_SET_WITH_PROGRAMSTATE(RefCountedParameters, const ParmVarDecl *)
+
+static const ParmVarDecl *getOriginParam(SVal V, CheckerContext &C,
+                                         bool IncludeBaseRegions = false) {
+  // TODO: We should most likely always include base regions here.
+  SymbolRef Sym = V.getAsSymbol(IncludeBaseRegions);
+  if (!Sym)
+    return nullptr;
+
+  // If we optimistically assume that the MIG routine never re-uses the storage
+  // that was passed to it as arguments when it invalidates it (but at most when
+  // it assigns to parameter variables directly), this procedure correctly
+  // determines if the value was loaded from the transitive closure of MIG
+  // routine arguments in the heap.
+  while (const MemRegion *MR = Sym->getOriginRegion()) {
+    const auto *VR = dyn_cast<VarRegion>(MR);
+    if (VR && VR->hasStackParametersStorage() &&
+           VR->getStackFrame()->inTopFrame())
+      return cast<ParmVarDecl>(VR->getDecl());
+
+    const SymbolicRegion *SR = MR->getSymbolicBase();
+    if (!SR)
+      return nullptr;
+
+    Sym = SR->getSymbol();
+  }
+
+  return nullptr;
+}
+
+static bool isInMIGCall(CheckerContext &C) {
+  const LocationContext *LC = C.getLocationContext();
+  assert(LC && "Unknown location context");
+
+  const StackFrameContext *SFC;
+  // Find the top frame.
+  while (LC) {
+    SFC = LC->getStackFrame();
+    LC = SFC->getParent();
+  }
+
+  const Decl *D = SFC->getDecl();
+
+  if (Optional<AnyCall> AC = AnyCall::forDecl(D)) {
+    // Even though there's a Sema warning when the return type of an annotated
+    // function is not a kern_return_t, this warning isn't an error, so we need
+    // an extra sanity check here.
+    // FIXME: AnyCall doesn't support blocks yet, so they remain unchecked
+    // for now.
+    if (!AC->getReturnType(C.getASTContext())
+             .getCanonicalType()->isSignedIntegerType())
+      return false;
+  }
+
+  if (D->hasAttr<MIGServerRoutineAttr>())
+    return true;
+
+  // See if there's an annotated method in the superclass.
+  if (const auto *MD = dyn_cast<CXXMethodDecl>(D))
+    for (const auto *OMD: MD->overridden_methods())
+      if (OMD->hasAttr<MIGServerRoutineAttr>())
+        return true;
+
+  return false;
+}
+
+void MIGChecker::checkPostCall(const CallEvent &Call, CheckerContext &C) const {
+  if (Call.isCalled(OsRefRetain)) {
+    // If the code is doing reference counting over the parameter,
+    // it opens up an opportunity for safely calling a destructor function.
+    // TODO: We should still check for over-releases.
+    if (const ParmVarDecl *PVD =
+            getOriginParam(Call.getArgSVal(0), C, /*IncludeBaseRegions=*/true)) {
+      // We never need to clean up the program state because these are
+      // top-level parameters anyway, so they're always live.
+      C.addTransition(C.getState()->add<RefCountedParameters>(PVD));
+    }
+    return;
+  }
+
+  if (!isInMIGCall(C))
+    return;
+
+  auto I = llvm::find_if(Deallocators,
+                         [&](const std::pair<CallDescription, unsigned> &Item) {
+                           return Call.isCalled(Item.first);
+                         });
+  if (I == Deallocators.end())
+    return;
+
+  ProgramStateRef State = C.getState();
+  unsigned ArgIdx = I->second;
+  SVal Arg = Call.getArgSVal(ArgIdx);
+  const ParmVarDecl *PVD = getOriginParam(Arg, C);
+  if (!PVD || State->contains<RefCountedParameters>(PVD))
+    return;
+
+  const NoteTag *T = C.getNoteTag([this, PVD](BugReport &BR) -> std::string {
+    if (&BR.getBugType() != &BT)
+      return "";
+    SmallString<64> Str;
+    llvm::raw_svector_ostream OS(Str);
+    OS << "Value passed through parameter '" << PVD->getName()
+       << "\' is deallocated";
+    return OS.str();
+  });
+  C.addTransition(State->set<ReleasedParameter>(true), T);
+}
+
+// Returns true if V can potentially represent a "successful" kern_return_t.
+static bool mayBeSuccess(SVal V, CheckerContext &C) {
+  ProgramStateRef State = C.getState();
+
+  // Can V represent KERN_SUCCESS?
+  if (!State->isNull(V).isConstrainedFalse())
+    return true;
+
+  SValBuilder &SVB = C.getSValBuilder();
+  ASTContext &ACtx = C.getASTContext();
+
+  // Can V represent MIG_NO_REPLY?
+  static const int MigNoReply = -305;
+  V = SVB.evalEQ(C.getState(), V, SVB.makeIntVal(MigNoReply, ACtx.IntTy));
+  if (!State->isNull(V).isConstrainedTrue())
+    return true;
+
+  // If none of the above, it's definitely an error.
+  return false;
+}
+
+void MIGChecker::checkReturnAux(const ReturnStmt *RS, CheckerContext &C) const {
+  // It is very unlikely that a MIG callback will be called from anywhere
+  // within the project under analysis and the caller isn't itself a routine
+  // that follows the MIG calling convention. Therefore we're safe to believe
+  // that it's always the top frame that is of interest. There's a slight chance
+  // that the user would want to enforce the MIG calling convention upon
+  // a random routine in the middle of nowhere, but given that the convention is
+  // fairly weird and hard to follow in the first place, there's relatively
+  // little motivation to spread it this way.
+  if (!C.inTopFrame())
+    return;
+
+  if (!isInMIGCall(C))
+    return;
+
+  // We know that the function is non-void, but what if the return statement
+  // is not there in the code? It's not a compile error, we should not crash.
+  if (!RS)
+    return;
+
+  ProgramStateRef State = C.getState();
+  if (!State->get<ReleasedParameter>())
+    return;
+
+  SVal V = C.getSVal(RS);
+  if (mayBeSuccess(V, C))
+    return;
+
+  ExplodedNode *N = C.generateErrorNode();
+  if (!N)
+    return;
+
+  auto R = std::make_unique<PathSensitiveBugReport>(
+      BT,
+      "MIG callback fails with error after deallocating argument value. "
+      "This is a use-after-free vulnerability because the caller will try to "
+      "deallocate it again",
+      N);
+
+  R->addRange(RS->getSourceRange());
+  bugreporter::trackExpressionValue(N, RS->getRetValue(), *R,
+                                    bugreporter::TrackingKind::Thorough, false);
+  C.emitReport(std::move(R));
+}
+
+void ento::registerMIGChecker(CheckerManager &Mgr) {
+  Mgr.registerChecker<MIGChecker>();
+}
+
+bool ento::shouldRegisterMIGChecker(const LangOptions &LO) {
+  return true;
+}