The udl_fb_mmap function in drivers/gpu/drm/udl/udl_fb.c at the Linux kernel version 3.4 and up to and including 4.15 has an integer-overflow vulnerability allowing local users with access to the udldrmfb driver to obtain full read and write permissions on kernel physical pages, resulting in a code execution in kernel space.
The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.