md(4) (swap-base) disks not cleaned on creation

[Dag-Erling Smørgrav]

Konstantin Belousov <kostikbel at gmail.com> writes:
> It is definitely not a security issue.

I disagree.  There may be legitimate reasons for root to create an md
and give read access to an unprivileged user, under the assumption that
it is zeroed; or to allow root in a jail to create mds.

> That said, the following patch should fix the nit. I am unsure about
> it, because it fixes mostly non-issue by spending CPU time to zero a
> page which would be either zeroed or overwritten right now anyway in
> normal usage.

You can at least partly mitigate this by adding VM_ALLOC_ZERO to the
flags passed to vm_page_grab() on line 666 and then checking the PG_ZERO
bit in m->flags.

DES
-- 
Dag-Erling Smørgrav - des at des.no