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Date: Wed, 8 Oct 2014 12:48:19 -0700
From: Andy Lutomirski <luto@...capital.net>
To: oss-security@...ts.openwall.com
Subject: CVE-2014-7970: Linux VFS denial of service

pivot_root has a bug.  Exploiting it at all is tricky, but it can be
done.  I'm reasonably confident that this is just denial of service.
(There's also probably an information disclosure in there, but I think
that it's only available to root, so it's not a big deal.)

I'm posting this a little bit early, since a patch is publicly
available, the impact is low, and hitting the bad code path at all is
quite tedious.  I'll send a proof of concept later on.

Distros: if you need a test case to validate the fix, let me know.
Although, for validation, it should be sufficient to just chroot
somewhere as root, escape the chroot (while still chrooted), and then
pivot_root(".", ".") on a mountpoint.

Candidate patch here:

http://news.gmane.org/find-root.php?message_id=87bnpmihks.fsf%40x220.int.ebiederm.org

-- 
Andy Lutomirski
AMA Capital Management, LLC

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