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Message-ID: <660663363.905981256240879655.JavaMail.root@zmail01.collab.prod.int.phx2.redhat.com>
Date: Thu, 22 Oct 2009 15:47:59 -0400 (EDT)
From: Josh Bressers <bressers@...hat.com>
To: oss-security@...ts.openwall.com
Cc: "Steven M. Christey" <coley@...us.mitre.org>
Subject: Re: CVE request: kernel: get_instantiation_keyring()
should inc the keyring refcount in all cases
Please use CVE-2009-3624 for this.
--
JB
----- "Eugene Teo" <eugeneteo@...nel.sg> wrote:
> Quoting from the upstream commit:
> "The destination keyring specified to request_key() and co. is made
> available to the process that instantiates the key (the slave process
>
> started by /sbin/request-key typically). This is passed in the
> request_key_auth struct as the dest_keyring member.
>
> keyctl_instantiate_key and keyctl_negate_key() call
> get_instantiation_keyring() to get the keyring to attach the newly
> constructed key to at the end of instantiation. This may be given a
> specific keyring into which a link will be made later, or it may be
> asked to find the keyring passed to request_key(). In the former
> case,
> it returns a keyring with the refcount incremented by
> lookup_user_key();
> in the latter case, it returns the keyring from the request_key_auth
> struct - and does _not_ increment the refcount.
>
> The latter case will eventually result in an oops when the keyring
> prematurely runs out of references and gets destroyed. The effect may
>
> take some time to show up as the key is destroyed lazily.
>
> To fix this, the keyring returned by get_instantiation_keyring() must
>
> always have its refcount incremented, no matter where it comes from."
>
> This was introduced in upstream commit 8bbf4976 (v2.6.29-rc1).
>
> References:
> http://git.kernel.org/linus/8bbf4976
> http://git.kernel.org/linus/21279cfa107af07ef985539ac0de2152b9cba5f5
> http://twitter.com/spendergrsec/status/4916661870
>
> Thanks, Eugene
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