[FLINK-9694] Potentially NPE in CompositeTypeSerializerConfigSnapshot constructor

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.5.0
• Fix Version/s: 1.5.3, 1.6.0
• Component/s: Table SQL / API
• Labels: pull-request-available
• Assignee: Piotr Nowojski
• Reporter: vinoyang
• Created: 30/Jun/18 06:29
• Updated: 01/Aug/18 13:04
• Resolved: 01/Aug/18 13:04

Description

the partial specific exception stack trace :

Caused by: java.lang.NullPointerException
at org.apache.flink.api.common.typeutils.CompositeTypeSerializerConfigSnapshot.<init>(CompositeTypeSerializerConfigSnapshot.java:53)
at org.apache.flink.table.runtime.types.CRowSerializer$CRowSerializerConfigSnapshot.<init>(CRowSerializer.scala:120)
at org.apache.flink.table.runtime.types.CRowSerializer$CRowSerializerConfigSnapshot.<init>(CRowSerializer.scala:123)
at sun.reflect.GeneratedConstructorAccessor10.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at java.lang.Class.newInstance(Class.java:442)
at org.apache.flink.util.InstantiationUtil.instantiate(InstantiationUtil.java:319)
... 20 more

related code is : 

public CompositeTypeSerializerConfigSnapshot(TypeSerializer<?>... nestedSerializers) {
   Preconditions.checkNotNull(nestedSerializers);

   this.nestedSerializersAndConfigs = new ArrayList<>(nestedSerializers.length);
   for (TypeSerializer<?> nestedSerializer : nestedSerializers) {
      TypeSerializerConfigSnapshot configSnapshot = nestedSerializer.snapshotConfiguration();
      this.nestedSerializersAndConfigs.add(
         new Tuple2<TypeSerializer<?>, TypeSerializerConfigSnapshot>(
            nestedSerializer.duplicate(),
            Preconditions.checkNotNull(configSnapshot)));
   }
}

exception happens at : 

TypeSerializerConfigSnapshot configSnapshot = nestedSerializer.snapshotConfiguration();

the reason is the type of constructor's parameter "..." used "varargs" feature. The  initialize code in CRowSerializer.scala is : 

def this() = this(null)    // Scala code

when invoked this, actually the the type of CompositeTypeSerializerConfigSnapshot's

nestedSerializers parameter is :

TypeSerializer<?>[] nestedSerializers = new TypeSerializer<?>[] {null};

so the checkNotNull precondition statement :

Preconditions.checkNotNull(nestedSerializers);

is always useless.

So we should check the object reference in for loop to protect NPE. 

Issue Links

• links to: GitHub Pull Request #6231
• links to: GitHub Pull Request #6392