Merge pull request #17880 from mikeash/fix-metadata-read-out-of-bounds-4.2

[Runtime][4.2] In various enumTagSinglePayload functions, don't read getExtraInhabitantIndex or storeExtraInhabitant unless it actually has extra inhabitants.

Author: mikeash

stdlib/public/runtime/Enum.cpp

@@ -144,9 +144,8 @@ unsigned swift::swift_getEnumCaseSinglePayload(const OpaqueValue *value,
   auto *payloadWitnesses = payload->getValueWitnesses();
   auto size = payloadWitnesses->getSize();
   auto numExtraInhabitants = payloadWitnesses->getNumExtraInhabitants();
-  auto getExtraInhabitantIndex =
-      (static_cast<const ExtraInhabitantsValueWitnessTable *>(payloadWitnesses)
-           ->getExtraInhabitantIndex);
+  auto EIVWT = dyn_cast<ExtraInhabitantsValueWitnessTable>(payloadWitnesses);
+  auto getExtraInhabitantIndex = EIVWT ? EIVWT->getExtraInhabitantIndex : nullptr;
 
   return getEnumTagSinglePayloadImpl(value, emptyCases, payload, size,
                                      numExtraInhabitants,
@@ -161,9 +160,8 @@ void swift::swift_storeEnumTagSinglePayload(OpaqueValue *value,
   auto *payloadWitnesses = payload->getValueWitnesses();
   auto size = payloadWitnesses->getSize();
   auto numExtraInhabitants = payloadWitnesses->getNumExtraInhabitants();
-  auto storeExtraInhabitant =
-      (static_cast<const ExtraInhabitantsValueWitnessTable *>(payloadWitnesses)
-           ->storeExtraInhabitant);
+  auto EIVWT = dyn_cast<ExtraInhabitantsValueWitnessTable>(payloadWitnesses);
+  auto storeExtraInhabitant = EIVWT ? EIVWT->storeExtraInhabitant : nullptr;
 
   storeEnumTagSinglePayloadImpl(value, whichCase, emptyCases, payload, size,
                                 numExtraInhabitants, storeExtraInhabitant);

stdlib/public/runtime/Metadata.cpp

@@ -1081,9 +1081,8 @@ static unsigned tuple_getEnumTagSinglePayload(const OpaqueValue *enumAddr,
   auto *witnesses = self->getValueWitnesses();
   auto size = witnesses->getSize();
   auto numExtraInhabitants = witnesses->getNumExtraInhabitants();
-  auto getExtraInhabitantIndex =
-      (static_cast<const ExtraInhabitantsValueWitnessTable *>(witnesses)
-           ->getExtraInhabitantIndex);
+  auto EIVWT = dyn_cast<ExtraInhabitantsValueWitnessTable>(witnesses);
+  auto getExtraInhabitantIndex = EIVWT ? EIVWT->getExtraInhabitantIndex : nullptr;
 
   return getEnumTagSinglePayloadImpl(enumAddr, numEmptyCases, self, size,
                                      numExtraInhabitants,
@@ -1097,9 +1096,8 @@ tuple_storeEnumTagSinglePayload(OpaqueValue *enumAddr, unsigned whichCase,
   auto *witnesses = self->getValueWitnesses();
   auto size = witnesses->getSize();
   auto numExtraInhabitants = witnesses->getNumExtraInhabitants();
-  auto storeExtraInhabitant =
-      (static_cast<const ExtraInhabitantsValueWitnessTable *>(witnesses)
-           ->storeExtraInhabitant);
+  auto EIVWT = dyn_cast<ExtraInhabitantsValueWitnessTable>(witnesses);
+  auto storeExtraInhabitant = EIVWT ? EIVWT->storeExtraInhabitant : nullptr;
 
   storeEnumTagSinglePayloadImpl(enumAddr, whichCase, numEmptyCases, self, size,
                                 numExtraInhabitants, storeExtraInhabitant);
@@ -1617,9 +1615,8 @@ static unsigned pod_direct_getEnumTagSinglePayload(const OpaqueValue *enumAddr,
   auto *witnesses = self->getValueWitnesses();
   auto size = witnesses->getSize();
   auto numExtraInhabitants = witnesses->getNumExtraInhabitants();
-  auto getExtraInhabitantIndex =
-      (static_cast<const ExtraInhabitantsValueWitnessTable *>(witnesses)
-           ->getExtraInhabitantIndex);
+  auto EIVWT = dyn_cast<ExtraInhabitantsValueWitnessTable>(witnesses);
+  auto getExtraInhabitantIndex = EIVWT ? EIVWT->getExtraInhabitantIndex : nullptr;
 
   return getEnumTagSinglePayloadImpl(enumAddr, numEmptyCases, self, size,
                                      numExtraInhabitants,
@@ -1633,9 +1630,8 @@ static void pod_direct_storeEnumTagSinglePayload(OpaqueValue *enumAddr,
   auto *witnesses = self->getValueWitnesses();
   auto size = witnesses->getSize();
   auto numExtraInhabitants = witnesses->getNumExtraInhabitants();
-  auto storeExtraInhabitant =
-      (static_cast<const ExtraInhabitantsValueWitnessTable *>(witnesses)
-           ->storeExtraInhabitant);
+  auto EIVWT = dyn_cast<ExtraInhabitantsValueWitnessTable>(witnesses);
+  auto storeExtraInhabitant = EIVWT ? EIVWT->storeExtraInhabitant : nullptr;
 
   storeEnumTagSinglePayloadImpl(enumAddr, whichCase, numEmptyCases, self, size,
                                 numExtraInhabitants, storeExtraInhabitant);

stdlib/public/runtime/MetadataImpl.h

@@ -925,10 +925,8 @@ struct NonFixedValueWitnesses :
                                           const Metadata *self) {
     auto *payloadWitnesses = self->getValueWitnesses();
     auto size = payloadWitnesses->getSize();
-    auto getExtraInhabitantIndex =
-        (static_cast<const ExtraInhabitantsValueWitnessTable *>(
-             payloadWitnesses)
-             ->getExtraInhabitantIndex);
+    auto EIVWT = dyn_cast<ExtraInhabitantsValueWitnessTable>(payloadWitnesses);
+    auto getExtraInhabitantIndex = EIVWT ? EIVWT->getExtraInhabitantIndex : nullptr;
 
     return getEnumTagSinglePayloadImpl(enumAddr, numEmptyCases, self, size,
                                        numExtraInhabitants,
@@ -942,10 +940,8 @@ struct NonFixedValueWitnesses :
     auto *payloadWitnesses = self->getValueWitnesses();
     auto size = payloadWitnesses->getSize();
     auto numExtraInhabitants = payloadWitnesses->getNumExtraInhabitants();
-    auto storeExtraInhabitant =
-        (static_cast<const ExtraInhabitantsValueWitnessTable *>(
-             payloadWitnesses)
-             ->storeExtraInhabitant);
+    auto EIVWT = dyn_cast<ExtraInhabitantsValueWitnessTable>(payloadWitnesses);
+    auto storeExtraInhabitant = EIVWT ? EIVWT->storeExtraInhabitant : nullptr;
 
     storeEnumTagSinglePayloadImpl(enumAddr, whichCase, numEmptyCases, self,
                                   size, numExtraInhabitants,