The tty_ldisc_hangup function in drivers/char/tty_ldisc.c in the Linux kernel 2.6.31-rc before 2.6.31-rc8 allows local users to cause a denial of service (system crash, sometimes preceded by a NULL pointer dereference) or possibly gain privileges via certain pseudo-terminal I/O activity, as demonstrated by KernelTtyTest.c.
git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commit%3Bh=5c58ceff103d8a654f24769bb1baaf84a841b0cc
lkml.org/lkml/2009/8/20/21
lkml.org/lkml/2009/8/20/27
lkml.org/lkml/2009/8/20/68
www.kernel.org/pub/linux/kernel/v2.6/testing/ChangeLog-2.6.31-rc8
www.openwall.com/lists/oss-security/2009/08/31/1
www.openwall.com/lists/oss-security/2009/09/03/6
www.openwall.com/lists/oss-security/2009/09/03/7
www.securityfocus.com/bid/36191