Clever attack exploits fully-patched Linux kernel

This is the part I find interesting (emphasis added):

The vulnerability is located in several parts of Linux, including one that implements functions known as net/tun. Although the code correctly checks to make sure the tun variable doesn’t point to NULL, the compiler removes the lines responsible for that inspection during optimization routines. The result: When the variable points to zero, the kernel tries to access forbidden pieces of memory, leading to a compromise of the box running the OS.

That sounds like a bug in the compiler’s optimization routines.