All posts by corbet

[$] Toward fast, containerized, user-space filesystems

Post Syndicated from corbet original https://lwn.net/Articles/1044432/

Filesystems are complex and performance-sensitive beasts. They can also
present security concerns. Microkernel-based systems have long pushed
filesystems into separate processes in order to contain any vulnerabilities
that may be found there. Linux can do the same with the Filesystem in
Userspace (FUSE) subsystem, but using FUSE brings a significant
performance penalty. Darrick Wong is working on ways to eliminate that
penalty, and he has a massive patch
set showing how ext4 filesystems can be safely implemented in user space by
unprivileged processes with good performance. This work has the potential
to radically change how filesystems are managed on Linux systems.

[$] LWN.net Weekly Edition for November 6, 2025

Post Syndicated from corbet original https://lwn.net/Articles/1044227/

Inside this week’s LWN.net Weekly Edition:

  • Front: Python thread safety; Namespace reference counting; Merigraf; Speeding up short reads; Julia 1.12; systemd security.
  • Briefs: CHERIoT 1.0; Chromium XSLT; Arm KASLR; Bazzite; Devuan 6.0; Incus 6.18; LXQt 2.3.0; Rust 1.91.0; Quotes; …
  • Announcements: Newsletters, conferences, security updates, patches, and more.

Defeating KASLR by Doing Nothing at All (Project Zero)

Post Syndicated from corbet original https://lwn.net/Articles/1044867/

The Project Zero blog explains
that, on 64-bit Arm systems, the kernel’s direct map is always placed at
the same virtual location, regardless of whether kernel address-space
layout randomization (KASLR) is enabled.

While it remains true that KASLR should not be trusted to prevent
exploitation, particularly in local contexts, it is regrettable
that the attitude around Linux KASLR is so fatalistic that putting
in the engineering effort to preserve its remaining integrity is
not considered to be worthwhile. The joint effect of these two
issues dramatically simplified what might otherwise have been a
more complicated and likely less reliable exploit.

[$] Namespace reference counting and listns()

Post Syndicated from corbet original https://lwn.net/Articles/1043824/

The kernel’s namespaces feature is, among
other things, a key part of the implementation of containers. Like much in
the kernel, though, the namespace API evolved over time; there was no
design at the outset. As a result, this API has some rough edges and
missing features. Christian Brauner is working to straighten out the
namespace situation somewhat with this
daunting 72-part patch series that, among other things, adds a new
system call to allow user space to query the namespaces present on the
system.

A new kernel port — to WebAssembly

Post Syndicated from corbet original https://lwn.net/Articles/1044786/

Joel Severin has announced
the availability of his port of the Linux kernel to WebAssembly; one can go
to this page and
watch it boot in a browser.

Wasm is similar to every other arch in Linux, but also
different. One important difference is that there is no way to
suspend execution of a task. There is a way around this though:
Linux supports up to 8k CPUs (or possibly more…). We can just
spin up a new CPU dedicated to each user task (process/thread) and
never preempt it

[$] The long path toward optimizing short reads

Post Syndicated from corbet original https://lwn.net/Articles/1043640/

The kernel’s file-I/O subsystems have been highly optimized over the years
in the hope of providing the best performance for a wide variety of
workloads. There is, however, one workload type that suffers with current
kernels: applications that perform many short reads, in multiple processes,
from the same file. Kiryl Shutsemau has been working on a patch to
try to optimize this case, but the task is turning out to be harder than
one might expect.

Python Software Foundation withdraws security-related grant proposal

Post Syndicated from corbet original https://lwn.net/Articles/1043563/

The Python Software Foundation, earlier this year, successfully obtained a
$1.5 million grant from the US National Science Foundation “to
address structural vulnerabilities in Python and PyPI“. The actual
grant came with some strings attached though, in the form of a requirement
not to pursue diversity, equity, and inclusion programs. So the Foundation
has withdrawn
the proposal rather than agree to terms that run counter to its own
mission.

We’re disappointed to have been put in the position where we had to
make this decision, because we believe our proposed project would
offer invaluable advances to the Python and greater open source
community, protecting millions of PyPI users from attempted
supply-chain attacks. The proposed project would create new tools
for automated proactive review of all packages uploaded to PyPI,
rather than the current process of reactive-only review.

Typst 0.14 released

Post Syndicated from corbet original https://lwn.net/Articles/1043242/

Version 0.14 of the
Typst document processor has been released.

If you need to comply with accessibility-related regulations, Typst
0.14 has your back. Typst now generates accessible documents by
default, with opt-in support for stricter checks. For those working
with complex illustrations, PDFs are now supported as a native
image format. In case you’re typesetting a book, the new
character-level justification will give your layout the final
touch. And if you’re building a website or blog, many improvements
to Typst’s HTML export are waiting for you.

LWN looked at Typst in September.

[$] Safer speculation-free user-space access

Post Syndicated from corbet original https://lwn.net/Articles/1042711/

The Spectre class of hardware vulnerabilities truly is a gift that keeps on
giving. New variants are still being discovered in current CPUs nearly
eight years after the disclosure of this
problem, and developers are still working to minimize the performance costs
that come from defending against it. The masked user-space access
mechanism is a case in point: it reduces the cost of defending against some
speculative attacks, but it brought some challenges of its own that are
only now being addressed.

[$] Git considers SHA-256, Rust, LLMs, and more

Post Syndicated from corbet original https://lwn.net/Articles/1042172/

The Git source-code management system is a foundational tool upon which
much of the free-software community is based. For many people, Git simply
works, though perhaps in quirky ways, so the activity of its development
community may not often appear on their radar. There is a lot happening in
the Git world at the moment, though, as the project works toward a 3.0
release sometime in 2026. Topics of interest in the Git community include
the SHA-256 transition, the introduction of code written in Rust, and how
the project should view contributions created with the assistance of large
language models.

DigiKam 8.8.0 released

Post Syndicated from corbet original https://lwn.net/Articles/1042823/

Version
8.8.0 of the digiKam photo-management system has been released.
“This version delivers significant improvements in performance,
stability, and user experience, with a particular focus on image
processing, color management, and workflow efficiency“. Changes
include an import/export feature for tag hierarchies, focus-point
visualization for some camera models, automatic use of the monitor color
profile, and a background-blur tool.

Security updates for Tuesday

Post Syndicated from corbet original https://lwn.net/Articles/1042822/

Security updates have been issued by AlmaLinux (.NET 8.0, firefox, kernel, kernel-rt, libssh, and perl-JSON-XS), Debian (ark and libphp-adodb), Fedora (chromium and gi-docgen), Mageia (quictls), Oracle (.NET 8.0, .NET 9.0, firefox, httpd, kernel, libsoup3, libssh, microcode_ctl, and webkit2gtk3), SUSE (go1.24, go1.25, krb5, python-ldap, and webkit2gtk3), and Ubuntu (gst-plugins-base1.0, linux, linux-aws, linux-gcp, linux-gke, linux-gkeop, linux-hwe-5.15,
linux-ibm, linux-ibm-5.15, linux-lowlatency, linux-lowlatency-hwe-5.15,
linux-nvidia, linux-oracle, linux-oracle-5.15, linux-xilinx-zynqmp, linux-fips, linux-aws-fips, linux-azure-fips, linux-gcp-fips,
linux-intel-iot-realtime, linux-realtime, and python-ldap).