The memory is used after released ??

Hi all,
This is Qianxin CodeSafe Team, we found a suspicious issue, at
https://github.com/google/leveldb/blob/23e35d792b9154f922b8b575b12596a4d8664c65/util/cache.cc#L316
Element "e" is used at
https://github.com/google/leveldb/blob/23e35d792b9154f922b8b575b12596a4d8664c65/util/cache.cc#L314
however，function “Unref” is defined at
https://github.com/google/leveldb/blob/23e35d792b9154f922b8b575b12596a4d8664c65/util/cache.cc#L226
where has freed e's memory

Start in util/cache.cc at the linked lines around the use of element "e" and the Unref definition. Trace the reference-counting and release paths to determine whether the reported access can occur after e is freed, then verify the result with an appropriate reproducer or test. Done means the report is confirmed with a regression test and corrected, or documented as not reproducible.

Written by the indexing model from the issue text.