CVE-2018-12633

An issue was discovered in the Linux kernel through 4.17.2.
vbg_misc_device_ioctl() in drivers/virt/vboxguest/vboxguest_linux.c reads
the same user data twice with copy_from_user. The header part of the user
data is double-fetched, and a malicious user thread can tamper with the
critical variables (hdr.size_in and hdr.size_out) in the header between the
two fetches because of a race condition, leading to severe kernel errors,
such as buffer over-accesses. This bug can cause a local denial of service
and information leakage.