All posts by corbet

[$] The first half of the 6.7 merge window

Post Syndicated from corbet original https://lwn.net/Articles/949294/

As of this writing, 9,842 non-merge changesets have found their way into
the mainline repository since the 6.7 merge window opened. Nearly a third
of those consist of the entire bcachefs development history but, even
discounting that, there has been a lot of material landing for the next
release. Read on for a summary of the most interesting changes pulled so
far in this development cycle.

[$] Guest-first memory for KVM

Post Syndicated from corbet original https://lwn.net/Articles/949277/

One of the core objectives of any confidential-computing implementation is
to protect a guest system’s memory from access by actors outside of the
guest itself. The host computer and hypervisor are part of the group that
is to be excluded from such access; indeed, they are often seen as
threat in their own right. Hardware vendors have added features like memory
encryption to make memory inaccessible to the host, but such features can
be difficult to use and are not available on all CPUs, so there is ongoing
interest in software-only solutions that can improve confidentiality. The
guest-first
memory patch set, posted by Sean Christopherson and containing work by
several developers, looks poised to bring some software-based protection to
an upcoming kernel release.

Evans: Confusing git terminology

Post Syndicated from corbet original https://lwn.net/Articles/949833/

Julia Evans has posted a list of
confusing Git terms and behavior along with explanations of what is
actually going on.

“Your branch is up to date with ‘origin/main’”

This message seems straightforward – it’s saying that your main branch is
up to date with the origin!

But it’s actually a little misleading. You might think that this means that
your main branch is up to date. It doesn’t. What it actually means is – if
you last ran git fetch or git pull 5 days ago, then your main branch is up
to date with all the changes as of 5 days ago.

So if you don’t realize that, it can give you a false sense of security.

Help wanted at LWN

Post Syndicated from corbet original https://lwn.net/Articles/949461/

LWN.net is looking to hire a full-time writer/editor to help us keep the
news flowing and to expand our content in areas of interest to our readers.
We are certain that the person we need is out there somewhere, and are
counting on help from LWN readers to find them. Read on for details on who
we are looking for and how we see them fitting in here.

Garrett: Why ACPI?

Post Syndicated from corbet original https://lwn.net/Articles/949625/

Matthew Garrett explains
why ACPI exists and why it is not as bad a thing as some think.

There’s an alternative universe where we decided to teach the
kernel about every piece of hardware it should run on. Fortunately
(or, well, unfortunately) we’ve seen that in the ARM world. Most
device-specific simply never reaches mainline, and most users are
stuck running ancient kernels as a result. Imagine every x86 device
vendor shipping their own kernel optimised for their hardware, and
now imagine how well that works out given the quality of their
firmware. Does that really seem better to you?

Security updates for Wednesday

Post Syndicated from corbet original https://lwn.net/Articles/949612/

Security updates have been issued by Debian (h2o, open-vm-tools, pmix, and zookeeper), Gentoo (GitPython), Oracle (firefox, java-11-openjdk, java-17-openjdk, libguestfs-winsupport, nginx:1.22, and thunderbird), Red Hat (samba), SUSE (container-suseconnect, libsndfile, and slurm), and Ubuntu (krb5, linux, linux-aws, linux-aws-5.15, linux-azure, linux-azure-5.15,
linux-azure-fde, linux-azure-fde-5.15, linux-gcp, linux-gcp-5.15,
linux-gkeop, linux-gkeop-5.15, linux-hwe-5.15, linux-ibm, linux-ibm-5.15,
linux-kvm, linux-lowlatency, linux-lowlatency-hwe-5.15, linux-nvidia,
linux-oracle, linux-oracle-5.15, linux, linux-aws, linux-aws-5.4, linux-azure, linux-azure-5.4,
linux-bluefield, linux-gcp, linux-gcp-5.4, linux-gkeop, linux-hwe-5.4,
linux-ibm, linux-ibm-5.4, linux-kvm, linux-oracle, linux-oracle-5.4,
linux-raspi, linux-raspi-5.4, linux-xilinx-zynqmp, linux, linux-aws, linux-aws-6.2, linux-azure, linux-azure-6.2,
linux-azure-fde-6.2, linux-gcp, linux-gcp-6.2, linux-hwe-6.2, linux-kvm,
linux-lowlatency, linux-lowlatency-hwe-6.2, linux-oracle, linux-raspi,
linux-starfive, linux-laptop, linux-nvidia-6.2, linux-oem-6.1, linux-raspi, open-vm-tools, and xorg-server).

Security updates for Tuesday

Post Syndicated from corbet original https://lwn.net/Articles/949391/

Security updates have been issued by Debian (jetty9, node-browserify-sign, request-tracker4, and request-tracker5), Fedora (golang-github-altree-bigfloat, golang-github-seancfoley-bintree, golang-github-seancfoley-ipaddress, kitty, slurm, and thunderbird), Gentoo (ConnMan, libxslt, and Salt), Mageia (chromium-browser-stable), Red Hat (firefox, libguestfs-winsupport, and thunderbird), SUSE (clamav, gcc13, gstreamer-plugins-bad, icu73_2, java-17-openjdk, nodejs10, poppler, python-Werkzeug, redis, thunderbird, webkit2gtk3, xorg-x11-server, and xwayland), and Ubuntu (kernel, linux-aws, linux-azure, linux-gcp, linux-oracle, linux-raspi, linux-iot, linux-raspi, linux-raspi-5.4, and mysql-8.0).

Bjarne Stroustrup’s Plan for Bringing Safety to C++ (The New Stack)

Post Syndicated from corbet original https://lwn.net/Articles/949269/

The New Stack covers
a conference talk by Bjarne Stroustrup on turning C++ into a safer
language.

Stroustrup has arrived at his solution: profiles. (That is, a set
of rules which, when followed, achieve specific safety guarantees.)
They’d be defined by the ISO C++ standard, addressing common safety
issues like pointers and array ranges. In response to a later
question from the audience about the difficulty of adding new
tooling, Stroustrup pointed out that the C++ compiler itself is now
a pretty sophisticated static analyzer, and could also be tasked
with meeting the profile’s requirements.

[$] Some 6.6 development statistics

Post Syndicated from corbet original https://lwn.net/Articles/948970/

The 6.6 kernel was released,
right on schedule, on October 29. This development cycle saw the
addition of 14,069 non-merge changesets from 1,978 developers — fairly
typical numbers for recent releases. The time has come for LWN’s
traditional look at where the changes in this release came from, along with
a look at the longer development “supercycle” that (probably) ends with
6.6.

The 6.6 kernel has been released

Post Syndicated from corbet original https://lwn.net/Articles/949179/

Linus has released the 6.6 kernel. “So
this last week has been pretty calm, and I have absolutely no excuses to
delay the v6.6 release any more, so here it is.”

Headline features in 6.6 include the earliest
eligible virtual deadline first (EEVDF) CPU scheduler, a number of
enhancements (quota support, user extended attributes, direct I/O) to the
tmpfs filesystem, the fchmodat2()
system call, initial support for building a
kernel without buffer-head support, the kmalloc() randomness patches, user-space shadow stacks for Intel CPUs, and
quite a bit more. See the LWN merge window summaries (part 1, part 2) and the KernelNewbies 6.6 page for
more information.

[$] Deferred scheduling for user-space critical sections

Post Syndicated from corbet original https://lwn.net/Articles/948870/

User-space developers working with highly threaded applications would often
like to be able to use spinlocks to protect shared data structures from
concurrent access. There is a fundamental problem with user-space
spinlocks, though: there is no way to prevent a thread from being
preempted. Various ways of working around this problem have been explored,
but this
patch from Steven Rostedt questions the premise on which much of that
work is based: what if it were possible to prevent preemption, for a
short period at least?

Removing syscall() from OpenBSD

Post Syndicated from corbet original https://lwn.net/Articles/949078/

For a view into the OpenBSD approach to security, see this message from
Theo de Raadt, where he describes a plan to remove the syscall() system call
(which allows the invocation of any available system call by providing its
number) from the kernel. The purpose, of course, is to make it harder for
an attacker to invoke an arbitrary system call, even if they are able to
run some code on the target system.

I hope I am forcing attack coders into using increasingly more
complicated methods. Same time, it means fewer methods are
available. Other methods make exploitation more fragile. This is
pushing success rates into “low-percent statistical” success. If
we teach more software stacks to “fail hard, don’t try to
recover”, that is an improvement in security.

[$] Better string handling for the kernel

Post Syndicated from corbet original https://lwn.net/Articles/948408/

The C programming language is replete with features that seemed like a good
idea at the time (and perhaps even were good ideas then) that have not aged
well. Most would likely agree that string handling, and the use of
NUL-terminated strings, is one of those. Kernel developers have, for
years, tried to improve the handling of strings in an attempt to slow the
flow of bugs and vulnerabilities that result from mistakes in that area.
Now there is an early discussion on the idea of moving away from
NUL-terminated strings in much of the kernel.

Security updates for Thursday

Post Syndicated from corbet original https://lwn.net/Articles/948930/

Security updates have been issued by Debian (firefox-esr and xorg-server), Fedora (firefox, mbedtls, nodejs18, nodejs20, and xen), Gentoo (libinput, unifi, and USBView), Mageia (python-nltk), Oracle (linux-firmware), Red Hat (nginx:1.22), SUSE (chromium, firefox, java-11-openjdk, jetty-minimal, nghttp2, nodejs18, webkit2gtk3, and zlib), and Ubuntu (linux, linux-lowlatency, linux-oracle-5.15, vim, and xorg-server, xwayland).