Spanner offers "external consistency", which is similar to linearizability.
CockroachDB offers serializability (as the default isolation level). Most other SQL databases offer serializability as their highest isolation level, but default to something weaker.
Serializability and linearizability are not equivalent, although it's not always easy to devise a scenario in which the differences are apparent. The "comments" tests in Aphyr's Jepsen analysis of CockroachDB is one such scenario: http://jepsen.io/analyses/cockroachdb-beta-20160829#comments
Linearizability is stronger; see the 'definition of linearizability' in https://en.wikipedia.org/wiki/Linearizability
Note: its been so long since I dealt with these things that I can't remember what the difference means in practice. :-)
Isn't that equivalent to serializability, which is a guarantee that lots of DBs offer (though you can choose weaker ones instead.)