drivers/input/serio/i8042.c in the Linux kernel before 4.12.4 allows attackers to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact because the port->exists value can change after it is validated.
git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=340d394a789518018f834ff70f7534fc463d3226
www.securityfocus.com/bid/102895
github.com/torvalds/linux/commit/340d394a789518018f834ff70f7534fc463d3226
usn.ubuntu.com/3655-1/
usn.ubuntu.com/3655-2/
www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.12.4