PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> Could not duplicate handle for "Global/PostgreSQL.xxxxxxxxxx": Bad file
> descriptor
That must be coming from dsm_impl_pin_segment or dsm_impl_unpin_segment;
noplace else has the same error message spelling.
> Error started after a pg_upgrade from 11.17 to 14.9 on the same physical
> servers.
Both those messages predate v11, so it's hard to tell what changed.
Are you sure the OS environment didn't change too?
regards, tom lane