When schema is changed, sstable set is updated according to the compaction strategy of the new schema (no changes to set are actually made, just the underlying set type is updated), but the problem is that it happens without a lock, causing a use-after-free when running concurrently to another set update.
Example:
1) A: sstable set is being updated on compaction completion
2) B: schema change updates the set (it's non deferring, so it happens in one go) and frees the set used by A.
3) when A resumes, system will likely crash since the set is freed already.
ASAN screams about it:
SUMMARY: AddressSanitizer: heap-use-after-free sstables/sstable_set.cc ...
Fix is about deferring update of the set on schema change to compaction, which is triggered after new schema is set. Only strategy state and backlog tracker are updated immediately, which is fine since strategy doesn't depend on any particular implementation of sstable set.
Fixes#22040.
Closesscylladb/scylladb#23680
* github.com:scylladb/scylladb:
replica: Fix use-after-free with concurrent schema change and sstable set update
sstables: Implement sstable_set_impl::all_sstable_runs()
e5d944f986