Any geom class using g_metadata_store, as well as geom_virstor which duplicated
g_metadata_store internally, would dump sectorsize - mdsize bytes of userspace
memory following the metadata block stored. This is most or all geom classes
(gcache, gconcat, geli, gjournal, glabel, gmirror, gmultipath, graid3, gshsec,
gstripe, and geom_virstor).

PR is public so there is no point cloak-and-daggering this review. Security
team individuals are marked as reviewers.

PR: 222077