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Tuesday, May 19th, 2020
| Time |
Event |
| 12:28p |
[$] Scheduler benchmarking with MMTests The MMTests benchmarking system is normally associated with its initial use case: testing memory-management changes. Increasingly, though, MMTests is not limited to memory management testing; at the 2020 Power Management and Scheduling
in the Linux Kernel summit (OSPM), Dario Faggioli talked about how he is using it to evaluate changes to the CPU scheduler, along with a discussion of the changes he had to make to get useful results for systems hosting virtualized guests. | | 2:30p |
Security updates for Tuesday
Security updates have been issued by Debian (dpdk and exim4), Fedora (openconnect, perl-Mojolicious, and php), Red Hat (kernel and kpatch-patch), Slackware (sane), and Ubuntu (bind9, dpdk, exim4, linux, linux-aws, linux-aws-hwe, linux-gcp, linux-gke-4.15, linux-hwe, linux-oem, linux-oracle, linux-snapdragon, and linux, linux-aws, linux-lts-xenial, linux-raspi2, linux-snapdragon). | | 4:59p |
[$] Evaluating vendor changes to the scheduler The kernel's CPU scheduler does its best to make the right decisions for just about any workload; over the years, it has been extended to better handle mobile-device scheduling as well. But handset vendors still end up applying their own patches to the scheduler for the kernels they ship. Shipping out-of-tree code in this way leads to a certain amount of criticism from the kernel community but, as Vincent Donnefort pointed out in his session at the 2020 Power Management and Scheduling
in the Linux Kernel summit (OSPM), those patches are applied for a reason. He looked at a set of vendor scheduler patches to see why they are being used. | | 7:04p |
NXNSAttack: upgrade resolvers to stop new kind of random subdomain attack CZ.NIC staff member Petr Špaček has a blog post describing a newly disclosed DNS resolver vulnerability called NXNSAttack. It allows attackers to abuse the delegation mechanism to create a denial-of-service condition via packet amplification. " This is so-called glueless delegation, i.e. a delegation which contains only names of authoritative DNS servers (a.iana-servers.net. and b.iana-servers.net.), but does not contain their IP addresses. Obviously DNS resolver cannot send a query to “name”, so the resolver first needs to obtain IPv4 or IPv6 address of authoritative server 'a.iana-servers.net.' or 'b.iana-servers.net.' and only then it can continue resolving the original query 'example.com. A'.
This glueless delegation is the basic principle of the NXNSAttack: Attacker simply sends back delegation with fake (random) server names pointing to victim DNS domain, thus forcing the resolver to generate queries towards victim DNS servers (in a futile attempt to resolve fake authoritative server names)." At this time, Ubuntu has updated its BIND package to mitigate the problem; other distributions will no doubt follow soon. More details can also be found in the paper [PDF]. | | 9:49p |
[$] The state of the AWK AWK is a text-processing language with a history spanning more than 40 years. It has a POSIX
standard, several conforming implementations, and is still surprisingly relevant in 2020 — both for simple text processing tasks and for wrangling "big data". The recent releaseof GNU Awk 5.1 seems like a good reason to survey the AWK landscape, see what GNU Awk has been up to, and look at where AWK is being used these days. |
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