Konstantin Belousov e9f581ba31 Zero the newly allocated md(4) swap-backed page to prevent random
kernel memory leakage to userspace. For the typical use, when a
filesystem put on the md disk, the change only results in CPU and
memory bandwidth spent to zero the page, since filsystems make sure
that user never see unwritten content.  But if md disk is used as raw
device by userspace, the garbage is exposed.

Reported by:	Paul Schenkeveld <freebsd@psconsult.nl>
MFC after:	2 weeks
2012-11-08 03:17:41 +00:00
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