CVE-2020-16166: Infoleak

A flaw was found in the way the Linux kernel derived the network RNG's internal state making the device ID predictable. Adding netrandstate (randomness) on interrupt and CPU activity makes speculation complicated by a remote observer.

This modifies the first 32 bits out of the 128 bits of a random CPU's netrandstate on interrupt or CPU activity to complicate remote observations that could lead to guessing the network RNG's internal state.

In addition, with NOHZ some CPUs might not even get timer interrupts, leaving their local state rarely updated, while they are running networked processes making use of the random state. For this reason, we also perform this update in updateprocesstimes() in order to at least update the state when there is user or system activity, since it's the only case we care about.

References: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=f227e3ec3b5cad859ad15666874405e8c1bbc1d4 https://github.com/torvalds/linux/commit/f227e3ec3b5cad859ad15666874405e8c1bbc1d4

— Red Hat

The Linux kernel through 5.7.11 allows remote attackers to make observations that help to obtain sensitive information about the internal state of the network RNG, aka CID-f227e3ec3b5c. This is related to drivers/char/random.c and kernel/time/timer.c.