Repeated call to pebbleIterator.Release accesses memory returned to sync.Pool

[magicxyyz]

System information

Commit hash : c8a2202 (current master)

Expected behaviour

pebbleIterator release should always succeed and can be called multiple times without causing error.

go-ethereum/ethdb/pebble/pebble.go

Lines 659 to 661 in 460cc16

	// Release releases associated resources. Release should always succeed and can
	// be called multiple times without causing error.
	func (iter *pebbleIterator) Release() { iter.iter.Close() }

Actual behaviour

Calling pebbleIterator.Release more then once will result in calling github.com/cockroachdb/pebble.Iterator.Close more then once, what is an invalid operation, as "it is not valid to call any method, including Close, after the iterator has been closed".

https://github.com/cockroachdb/pebble/blob/aa077af625936fb6b52d8efdd1a8bcf7070a1509/iterator.go#L2225-L2229

Second call to pebble.Iterator.Close will result in access to memory that was returned to sync.Pool and may have already been acquired by another iterator in another goroutine.

https://github.com/cockroachdb/pebble/blob/aa077af625936fb6b52d8efdd1a8bcf7070a1509/iterator.go#L2327-L2327

https://github.com/cockroachdb/pebble/blob/aa077af625936fb6b52d8efdd1a8bcf7070a1509/db.go#L1045-L1049