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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