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LWN.net is a comprehensive source of news and opinions from and about the Linux community. This is the main LWN.net feed, listing all articles which are posted to the site front page.
Updated: 5 hours 30 min ago

[$] DMA and get_user_pages()

7 hours 32 min ago

In the RDMA microconference of the 2018 Linux Plumbers Conference (LPC), John Hubbard, Dan Williams, and Matthew Wilcox led a discussion on the problems surrounding get_user_pages() (and friends) and the interaction with DMA. It is not the first time the topic has come up, there was also a discussion about it at the Linux Storage, Filesystem, and Memory-Management Summit back in April. In a nutshell, the problem is that multiple parts of the kernel think they have responsibility for the same chunk of memory, but they do not coordinate their activities; as might be guessed, mayhem can sometimes ensue.

The x32 subarchitecture may be removed

7 hours 35 min ago
The x32 subarchitecture is a software variant of x86-64; it runs the processor in the 64-bit mode, but uses 32-bit pointers and arithmetic. The idea is to get the advantages of x86-64 without the extra memory usage that goes along with it. It seems, though, that x32 is not much appreciated; few distributions support it and the number of users appears to be small. So now Andy Lutomirski is proposing its eventual removal:

I propose that we make CONFIG_X86_X32 depend on BROKEN for a release or two and then remove all the code if no one complains. If anyone wants to re-add it, IMO they're welcome to do so, but they need to do it in a way that is maintainable.

If there are x32 users out there, now would be a good time for them to speak up.

Security updates for Wednesday

8 hours 41 min ago
Security updates have been issued by Arch Linux (chromium, firefox, lib32-openssl, lib32-openssl-1.0, openssl, openssl-1.0, texlive-bin, and wireshark-cli), Fedora (perl), openSUSE (pdns), Oracle (kernel), Red Hat (kernel), Slackware (mozilla), SUSE (kernel, postgresql10, qemu, and xen), and Ubuntu (firefox, freerdp, freerdp2, pixman, and poppler).

Git 2.20.0 released

15 hours 38 min ago
Git 2.20.0 is out. Changes include interdiff generation support in git format-patch, an improved ability to cope with corrupted patches in git am, a number of performance and usability improvements, and more.

Firefox 64 released

Tuesday 11th of December 2018 07:49:15 PM
The Mozilla Blog takes a look at the Contextual Feature Recommender (CFR) in Firefox 64. "Aimed at people who are looking to get more out of their online experience or ways to level up. CFR is a system that proactively recommends Firefox features and add-ons based on how you use the web. For example, if you open multiple tabs and repeatedly use these tabs, we may offer a feature called “Pinned Tabs” and explain how it works. Firefox curates the suggested features and notifies you. With today’s release, we will start to rollout with three recommended extensions which include: Facebook Container, Enhancer for YouTube and To Google Translate. This feature is available for US users in regular browsing mode only. They will not appear in Private Browsing mode. Also, Mozilla does NOT receive a copy of your browser history. The entire process happens locally in your copy of Firefox." The release notes contain more details about this release.

[$] Large files with Git: LFS and git-annex

Tuesday 11th of December 2018 07:43:47 PM

Git does not handle large files very well. While there is work underway to handle large repositories through the commit graph work, Git's internal design has remained surprisingly constant throughout its history, which means that storing large files into Git comes with a significant and, ultimately, prohibitive performance cost. Thankfully, other projects are helping Git address this challenge. This article compares how Git LFS and git-annex address this problem and should help readers pick the right solution for their needs.

Security updates for Tuesday

Tuesday 11th of December 2018 04:14:41 PM
Security updates have been issued by Debian (php7.0), Fedora (keepalived, kernel, kernel-headers, kernel-tools, mingw-uriparser, and uriparser), openSUSE (pdns-recursor), Oracle (kernel), SUSE (compat-openssl098, glibc, java-1_8_0-ibm, kernel, opensc, python, python-base, python-cryptography, python-pyOpenSSL, samba, and soundtouch), and Ubuntu (cups).

[$] Measuring container security

Tuesday 11th of December 2018 02:55:51 PM

There are a lot of claims regarding the relative security of containers versus virtual machines (VMs), but there has been little in the way of actually trying to measure those differences. James Bottomley gave a talk in the refereed track of the 2018 Linux Plumbers Conference (LPC) that described work that targets filling in that gap. He and his colleagues have come up with a measure that, while not perfect, gives a starting point for further efforts.

Nextcloud 15 released

Tuesday 11th of December 2018 08:35:10 AM
Version 15 of the Nextcloud productivity and communications platform is out. New features include Mastodon integration, two-factor authentication, a number of user-interface improvements, and more.

Hutterer: Understanding HID report descriptors

Tuesday 11th of December 2018 08:19:31 AM
For those who would like a deeper understanding of how the human interface device (HID) protocol works, Peter Hutterer has posted a detailed overview. "Originally HID was designed to work over USB. But just like Shrek the technology world is obsessed with layers so these days HID works over different transport layers. HID over USB is what your mouse uses, HID over i2c may be what your touchpad uses. HID works over Bluetooth and it's celebrity-diet version BLE. Somewhere, someone out there is very slowly moving a mouse pointer by sending HID over carrier pigeons just to prove a point. Because there's always that one guy."

[$] A filesystem corruption bug breaks loose

Monday 10th of December 2018 05:58:42 PM
Kernel bugs can have all kinds of unfortunate consequences, from inconvenient crashes to nasty security vulnerabilities. Some of the most feared bugs, though, are those that corrupt data in filesystems. The losses imposed on users can be severe, and the resulting problems may not be noticed for a long time, making recovery difficult. Filesystem developers, knowing that they will have to face their users in the real world, go to considerable effort to prevent this kind of bug from finding its way into a released kernel. A recent failure in that regard raises a number of interesting questions about how kernel development is done.

Security updates for Monday

Monday 10th of December 2018 03:57:17 PM
Security updates have been issued by Debian (chromium-browser and lxml), Fedora (cairo, hadoop, and polkit), Mageia (tomcat), openSUSE (apache2-mod_jk, Chromium, dom4j, ImageMagick, libgit2, messagelib, ncurses, openssl-1_0_0, otrs, pam, php5, php7, postgresql10, rubygem-activejob-5_1, tiff, and tomcat), Red Hat (chromium-browser and rh-git218-git), Slackware (php), SUSE (audiofile, cri-o and kubernetes packages, cups, ImageMagick, libwpd, SMS3.2, and systemd), and Ubuntu (lxml).

Kernel prepatch 4.20-rc6

Monday 10th of December 2018 07:52:47 AM
The 4.20-rc6 kernel prepatch is out for testing. "Most of it looks pretty small and normal. Would I have preferred for there to be less churn? Yes. But it's certainly smaller than rc5 was, so we're moving in the right direction, and we have at least one more rc to go."

More stable kernel updates

Saturday 8th of December 2018 06:34:40 PM
The stable kernel process continues to churn out releases; 4.19.8, 4.14.87, and 4.9.144 are now available with another set of important fixes.

[$] Kernel quality control, or the lack thereof

Friday 7th of December 2018 06:28:33 PM
Filesystem developers tend toward a high level of conservatism when it comes to making changes; given the consequences of mistakes, this seems like a healthy survival trait. One might rightly be tempted to regard a recent disagreement over the backporting of filesystem-related fixes to the stable kernels as an example of this conservatism, but there is more to it. The kernel development process has matured in many ways over the years; perhaps this discussion hints at some of the changes that will be needed to continue that maturation in the future.

Security updates for Friday

Friday 7th of December 2018 04:05:09 PM
Security updates have been issued by Arch Linux (jupyter-notebook), CentOS (ghostscript), Debian (libphp-phpmailer and policykit-1), Fedora (bird), Gentoo (ede), Mageia (flash-player-plugin), openSUSE (dom4j, dpdk, glib2, nextcloud, postgresql94, and qemu), Oracle (kernel), SUSE (firefox, libarchive, libgit2, libreoffice, ncurses, openssl-1_0_0, squid, and tiff), and Ubuntu (ghostscript, openssl, openssl1.0, and wavpack).

[$] Toward race-free process signaling

Thursday 6th of December 2018 06:51:45 PM
Signals have existed in Unix systems for years, despite the general consensus that they are an example of a bad design. Extensions and new ways of using signals pop up from time to time, fixing the issues that have been found. A notable addition was the introduction of signalfd() nearly 10 years ago. Recently, the kernel developers have discussed how to avoid race conditions related to process-ID (PID) recycling, which occurs when a process terminates and another one is assigned the same PID. A process that fails to notice that its target has exited may try to send a signal to the wrong recipient, with potentially grave consequences. A patch set from Christian Brauner is trying to solve the issue by adding signaling via file descriptors.

Microsoft's Edge browser moving to Chromium

Thursday 6th of December 2018 05:35:39 PM
Microsoft has announced that its "Edge" browser is joining the Chromium world. "Today we’re announcing that we intend to adopt the Chromium open source project in the development of Microsoft Edge on the desktop to create better web compatibility for our customers and less fragmentation of the web for all web developers. As part of this, we intend to become a significant contributor to the Chromium project, in a way that can make not just Microsoft Edge — but other browsers as well — better on both PCs and other devices."

Security updates for Thursday

Thursday 6th of December 2018 02:42:13 PM
Security updates have been issued by Mageia (kio-extras), Red Hat (flash-plugin and openstack-neutron), Slackware (gnutls and nettle), SUSE ( aphp53, apache2, apache2-mod_jk, compat-openssl097g, firefox, llvm4, mozilla-nspr, mozilla-nss, apache2-mod_nss, glib2, kvm, mariadb, ncurses, openssl-1_0_0, openssl1, pam, php5, php7, qemu, rubygem-activejob-5_1, tomcat, and wireshark), and Ubuntu (libraw and spamassassin).

[$] LWN.net Weekly Edition for December 6, 2018

Thursday 6th of December 2018 01:35:19 AM
The LWN.net Weekly Edition for December 6, 2018 is available.