Fernando Rodrigues
856fb3c740
Xen Security Advisory CVE-2025-58150 / XSA-477
x86: buffer overrun with shadow paging + tracing
Shadow mode tracing code uses a set of per-CPU variables to avoid
cumbersome parameter passing. Some of these variables are written to
with guest controlled data, of guest controllable size. That size can
be larger than the variable, and bounding of the writes was missing.
The exact effects depend on what's adjacent to the variables in
question. The most likely effects are bogus trace data, but none of
privilege escalation, information leaks, or Denial of Service (DoS) can
be excluded without detailed analysis of the particular build of Xen.
Only x86 systems are vulnerable. Arm systems are not vulnerable.
Only HVM guests running in shadow paging mode and with tracing enabled
can leverage the vulnerability.
Running HVM guests in HAP mode only will avoid the vulnerability.
Not enabling tracing will also avoid the vulnerability. Tracing is
enabled by the "tbuf_size=" command line option, or by running tools
like xentrace or xenbaked in Dom0. Note that on a running system
stopping xentrace / xenbaked would disable tracing. For xentrace,
however, this additionally requires that it wasn't started with the -x
option. Stopping previously enabled tracing can of course only prevent
future damage; prior damage may have occurred and may manifest only
later.
This issue was discovered by Jan Beulich of SUSE.
https://xenbits.xenproject.org/xsa/advisory-477.html
Signed-off-by: Fernando Rodrigues <alpha@sigmasquadron.net>
Nixpkgs is a collection of over 120,000 software packages that can be installed with the Nix package manager. It also implements NixOS, a purely-functional Linux distribution.
Manuals
- NixOS Manual - how to install, configure, and maintain a purely-functional Linux distribution
- Nixpkgs Manual - contributing to Nixpkgs and using programming-language-specific Nix expressions
- Nix Package Manager Manual - how to write Nix expressions (programs), and how to use Nix command line tools
Community
- Discourse Forum
- Matrix Chat
- Official wiki
- Community-maintained list of ways to get in touch (Discord, Telegram, IRC, etc.)
Other Project Repositories
The sources of all official Nix-related projects are in the NixOS organization on GitHub. Here are some of the main ones:
- Nix - the purely functional package manager
- NixOps - the tool to remotely deploy NixOS machines
- nixos-hardware - NixOS profiles to optimize settings for different hardware
- Nix RFCs - the formal process for making substantial changes to the community
- NixOS homepage - the NixOS.org website
- hydra - our continuous integration system
- NixOS Branding - NixOS branding
Continuous Integration and Distribution
Nixpkgs and NixOS are built and tested by our continuous integration system, Hydra.
- Continuous package builds for unstable/master
- Continuous package builds for the NixOS 25.11 release
- Tests for unstable/master
- Tests for the NixOS 25.11 release
Artifacts successfully built with Hydra are published to cache at https://cache.nixos.org/. When successful build and test criteria are met, the Nixpkgs expressions are distributed via Nix channels.
Contributing
Nixpkgs is among the most active projects on GitHub. While thousands of open issues and pull requests might seem like a lot at first, it helps to consider it in the context of the scope of the project. Nixpkgs describes how to build tens of thousands of pieces of software and implements a Linux distribution. The GitHub Insights page gives a sense of the project activity.
Community contributions are always welcome through GitHub Issues and Pull Requests.
For more information about contributing to the project, please visit the contributing page.
Donations
The infrastructure for NixOS and related projects is maintained by a nonprofit organization, the NixOS Foundation. To ensure the continuity and expansion of the NixOS infrastructure, we are looking for donations to our organization.
You can donate to the NixOS foundation through SEPA bank transfers or by using Open Collective:
License
Nixpkgs is licensed under the MIT License.
Note
MIT license does not apply to the packages built by Nixpkgs, merely to the files in this repository (the Nix expressions, build scripts, NixOS modules, etc.). It also might not apply to patches included in Nixpkgs, which may be derivative works of the packages to which they apply. The aforementioned artifacts are all covered by the licenses of the respective packages.