Candidate: CVE-2009-3624
Description:
 "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."
References:
http://git.kernel.org/linus/8bbf4976
http://git.kernel.org/linus/21279cfa107af07ef985539ac0de2152b9cba5f5
http://twitter.com/spendergrsec/status/4916661870
Notes:
 jmm> Introduced in 2.6.29-rc1
Bugs:
upstream: released (2.6.32-rc5) [21279cfa107af07ef985539ac0de2152b9cba5f5], released (2.6.31.6) [7a99333e851ef087c7cd836950900602f0843c24]
linux-2.6: released (2.6.31-2)
2.6.18-etch-security: N/A
2.6.24-etch-security: N/A
2.6.26-lenny-security: N/A