Multiple race conditions in the terminal layer in Linux 2.4.x and 2.6.x before 2.6.9 allow (1) local users to obtain portions of kernel data via a TIOCSETD ioctl call to a terminal interface that is being accessed by another thread or (2) remote attackers to cause a denial of service (panic) by switching from console to PPP line discipline then quickly sending data that is received during the switch.