Linux kernel backports

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 Basics 13/13

  • Identification

    The Linux kernel backports project automatically backports the Linux kernel, it provide drivers released on newer kernels backported for usage on older kernels.

    What programming language(s) are used to implement the project?
  • Basic project website content


    The project website MUST succinctly describe what the software does (what problem does it solve?). [description_good]

    The project website MUST provide information on how to: obtain, provide feedback (as bug reports or enhancements), and contribute to the software. [interact]

    The information on how to contribute MUST explain the contribution process (e.g., are pull requests used?) (URL required) [contribution]

    https://backports.wiki.kernel.org/index.php/Documentation/backports/hacking

    Developer's Certificate of Origin 1.1 is used, from the Linux kernel.



    The information on how to contribute SHOULD include the requirements for acceptable contributions (e.g., a reference to any required coding standard). (URL required) [contribution_requirements]
  • FLOSS license

    What license(s) is the project released under?



    The software produced by the project MUST be released as FLOSS. [floss_license]

    It is SUGGESTED that any required license(s) for the software produced by the project be approved by the Open Source Initiative (OSI). [floss_license_osi]


    The project MUST post the license(s) of its results in a standard location in their source repository. (URL required) [license_location]
  • Documentation


    The project MUST provide basic documentation for the software produced by the project. [documentation_basics]

    The project MUST provide reference documentation that describes the external interface (both input and output) of the software produced by the project. [documentation_interface]

    The backports project is a subset of the Linux kernel, as such what you get out of it are Linux kernel modules or a kernel with newer drivers from a future version of Linux backported for your choice of Linux. Users can opt to download and install a packaged release, or to use the backports infrastructure for direct kernel integration. Both interfaces are documented separately:

    https://backports.wiki.kernel.org/index.php/Documentation/packaging https://backports.wiki.kernel.org/index.php/Documentation/integration

    The way this works and how this is possible is best documented through the developer documentation:

    https://backports.wiki.kernel.org/index.php/Documentation/backports/hacking

    The technical details in more elaborate detail is provided in paper form:

    http://coccinelle.lip6.fr/papers/backport_edcc15.pdf


  • Other


    The project sites (website, repository, and download URLs) MUST support HTTPS using TLS. [sites_https]

    https://www.kernel.org/pub/linux/kernel/projects/backports/ https://git.kernel.org/pub/scm/linux/kernel/git/backports/backports.git

    There is temporary "splash" page generated automatically here:

    http://drvbp1.linux-foundation.org/~mcgrof/rel-html/backports/

    However this does not use https, and is simply temporary. If we need a permanent splash page we can work on that, the tool, rel-html, used to generate the splash page just needs to be extended to automatically infer release by using PGP, PGP signed tags, and PGP signed tags for release deprecation.



    The project MUST have one or more mechanisms for discussion (including proposed changes and issues) that are searchable, allow messages and topics to be addressed by URL, enable new people to participate in some of the discussions, and do not require client-side installation of proprietary software. [discussion]

    A mailing list is public: backports@vger.kernel.org

    The archive: http://marc.info/?l=linux-backports

    To subscribe send an e-mail to majordomo@vger.kernel.org with anything on the subject and with this on the body of the e-mail: subscribe backports

    This is all documented here:

    https://backports.wiki.kernel.org/index.php/Mailing_list



    The project SHOULD provide documentation in English and be able to accept bug reports and comments about code in English. [english]

    We use the kernel.org bugzilla, users must select the Backports project section, or can use this URL directly:

    https://bugzilla.kernel.org/enter_bug.cgi?product=Backports%20project

    This is all documented for users here:

    https://backports.wiki.kernel.org/index.php/Documentation/reporting-bugs https://backports.wiki.kernel.org/index.php/Bugzilla



    The project MUST be maintained. [maintained]


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  • Public version-controlled source repository


    The project MUST have a version-controlled source repository that is publicly readable and has a URL. [repo_public]

    The project's source repository MUST track what changes were made, who made the changes, and when the changes were made. [repo_track]

    https://git.kernel.org/pub/scm/linux/kernel/git/backports/backports.git

    All changes go into the git repository. We track the changes, who made the changes, when the changes were made. Other than this we also track who merged the change. We have two key maintainers:

    Hauke Mehrtens Luis R. Rodriguez

    The repository is shared on kernel.org between both of these maintainers, they coordinate via IRC and e-mail about when one can / should merge changes.



    To enable collaborative review, the project's source repository MUST include interim versions for review between releases; it MUST NOT include only final releases. [repo_interim]

    The project mirrors Linux's own release mechanisms. The project relies on linux-next to generate snapshot releases based on the latest development efforts both on Linux and on the Linux backports project, these are the linux-next based snapshots. Once Linus releases a kernel as a release candidate the backports project follows with a respective release candidate for it. Once Linus blesses a final release a respective backports project follows through with a respective final release.

    During the development phase of Linux we have daily linux-next based snapshots, these are dated, the latest one being based on linux-next tag next-20160122, and so the respective backports release is:

    https://www.kernel.org/pub/linux/kernel/projects/backports/2016/01/22/backports-20160122.tar.gz

    Packaged releases are also made to mirror Linux stable releases, so for instance we have the v3.10-rc1 release:

    https://www.kernel.org/pub/linux/kernel/projects/backports/stable/v3.10-rc1/

    Then the v3.10 final release:

    https://www.kernel.org/pub/linux/kernel/projects/backports/stable/v3.10/

    After that we have follow up fixes to upstream Linux, and then a respective backports release for it, there were 3 extra version releases for v3.10:

    https://www.kernel.org/pub/linux/kernel/projects/backports/stable/v3.10.4/ https://www.kernel.org/pub/linux/kernel/projects/backports/stable/v3.10.17/ https://www.kernel.org/pub/linux/kernel/projects/backports/stable/v3.10.19/

    If the need ever arises to make a backports release update between the same snapshot of Linux a postfix digit is used to annotate this. For instance, we had two v3.8-rc2 releases, -1 and -2:

    https://www.kernel.org/pub/linux/kernel/projects/backports/stable/v3.8-rc2/compat-drivers-3.8-rc2-1.tar.bz2 https://www.kernel.org/pub/linux/kernel/projects/backports/stable/v3.8-rc2/compat-drivers-3.8-rc2-2.tar.bz2



    It is SUGGESTED that common distributed version control software be used (e.g., git) for the project's source repository. [repo_distributed]
  • Unique version numbering


    The project results MUST have a unique version identifier for each release intended to be used by users. [version_unique]

    The release tags for backports mirror the Linux kernel release scheme. When releases are made based on linux-next, the respective tag is used but instead of "next", "backports" is used. So for instance, a release based on linux-next next-20160122 would have a tag "backports-20160122".

    For stable releases the same Linux versioning scheme is followed, starting with release candidates (v3.10-rc1-1, v3.10-rc1-2), to final version (v3.10-1, v3.10-2), to extra version stable updates (v3.10.4-1, v3.10.19-1):

    v3.10-1 v3.10-2 v3.10-rc1-1 v3.10-rc1-2 v3.10.17-1 v3.10.17-2 v3.10.19-1 v3.10.4-1

    Since this project builds on Linux, we needed a way to distinguish between backport specific releases. This is accounted for the extra dash followed by the release number, so v3.10-1, v3.10-2, both -1 and -2 are backport specific annotations.



    It is SUGGESTED that the Semantic Versioning (SemVer) or Calendar Versioning (CalVer) version numbering format be used for releases. It is SUGGESTED that those who use CalVer include a micro level value. [version_semver]

    The Linux kernel does not make API changes that affect userspace, so there is no need to have denote api compatibility, it is always stable.



    It is SUGGESTED that projects identify each release within their version control system. For example, it is SUGGESTED that those using git identify each release using git tags. [version_tags]
  • Release notes


    The project MUST provide, in each release, release notes that are a human-readable summary of major changes in that release to help users determine if they should upgrade and what the upgrade impact will be. The release notes MUST NOT be the raw output of a version control log (e.g., the "git log" command results are not release notes). Projects whose results are not intended for reuse in multiple locations (such as the software for a single website or service) AND employ continuous delivery MAY select "N/A". (URL required) [release_notes]

    Since the backports project mirrors Linux the ChangeLog of Linux is referred to for changes, backport specific updates are too many to list, but major updates are referenced when a release is made, and the respective project README is updated to account for subsystems that are backported. This is available here:

    https://git.kernel.org/cgit/linux/kernel/git/backports/backports.git/tree/README

    When a new device driver is added it is mentioned only in the commit logs, we could do a better job at not only annotating subsystems but also device drivers, this becomes tricky however as we backport over 700 device drivers now. We will discuss what things we can do better to improve on this area.



    The release notes MUST identify every publicly known run-time vulnerability fixed in this release that already had a CVE assignment or similar when the release was created. This criterion may be marked as not applicable (N/A) if users typically cannot practically update the software themselves (e.g., as is often true for kernel updates). This criterion applies only to the project results, not to its dependencies. If there are no release notes or there have been no publicly known vulnerabilities, choose N/A. [release_notes_vulns]

    The backports project builds on top of Linux, the amount of backports specific code accounts for about 1%-2% of the code used. Although there is a risk of a security issue within backports, the major attack surface consists of non-backports related code: device drivers, or libraries carried over. Security fixes from Linux are carried over, we do not explicitly mirror the changelog of Linux, instead refer people to Linux' own changelog for security fixes on Linux.


  • Bug-reporting process


    The project MUST provide a process for users to submit bug reports (e.g., using an issue tracker or a mailing list). (URL required) [report_process]

    The project SHOULD use an issue tracker for tracking individual issues. [report_tracker]

    The "Backports project" section of bugzilla is used.



    The project MUST acknowledge a majority of bug reports submitted in the last 2-12 months (inclusive); the response need not include a fix. [report_responses]

    Example of latest fixes:

    https://bugzilla.kernel.org/show_bug.cgi?id=105921 https://bugzilla.kernel.org/show_bug.cgi?id=71501 https://bugzilla.kernel.org/show_bug.cgi?id=66601 https://bugzilla.kernel.org/show_bug.cgi?id=65881

    Sadly most reports are bogus. Most issues are actually reported on the mailing list and addressed there. There is no metric to address the number of issues mentioned on the mailing list and fixed there. We however do have an archive.



    The project SHOULD respond to a majority (>50%) of enhancement requests in the last 2-12 months (inclusive). [enhancement_responses]

    The mailing list is used for this and requests to add new drivers considered and discussed.



    The project MUST have a publicly available archive for reports and responses for later searching. (URL required) [report_archive]

    Bugzilla is used:

    https://backports.wiki.kernel.org/index.php/Bugzilla

    The project also has mailing list and that is archivedi

    https://backports.wiki.kernel.org/index.php/Mailing_list


  • Vulnerability report process


    The project MUST publish the process for reporting vulnerabilities on the project site. (URL required) [vulnerability_report_process]

    https://backports.wiki.kernel.org/index.php/Reporting-vulnerabilities

    This explains the process to follow to report vulnerabilities.



    If private vulnerability reports are supported, the project MUST include how to send the information in a way that is kept private. (URL required) [vulnerability_report_private]

    It is requested private vulnerabilities are reported via e-mail directly to the Linux backports maintainers. This is documented here:

    https://backports.wiki.kernel.org/index.php/Reporting-vulnerabilities



    The project's initial response time for any vulnerability report received in the last 6 months MUST be less than or equal to 14 days. [vulnerability_report_response]

    We have not had any vulnerabilities reported.


  • Working build system


    If the software produced by the project requires building for use, the project MUST provide a working build system that can automatically rebuild the software from source code. [build]

    Since Linux backports mirrors Linux, the build testing / automatic builds are borrowed, so linux-next daily builds are done by IBM, likewise, Intel's 0-day test infrastructure . There is no home page to linux-next daily builds tests, but its known that this merges all development trees and there is a compile test done daily. 0-day's home page:

    https://01.org/lkp

    Other than this currently backports build tests are done prior to each release, since all supported kernels need to be tested against, currently 24 kernels need to be compile tested against, compile testing with all features enabled takes a long time. HP, Linux Foundation, and SUSE donated a server to help with this, we grant access to key developers to help build test prior to making a release, or when incorporating a patch to test the build.

    We will work on automating builds though this may be a bit complex given the overhead.



    It is SUGGESTED that common tools be used for building the software. [build_common_tools]

    All required tools are free and open source software. The same tools to build Linux are the same tools to build backports Linux releases, with the addition of Coccinelle needed to generate packages for users. Only developers need coccinelle. Needed tools to build Linux backports packages:

    make gcc python perl

    When using integration the kernel is built as you typically would otherwise build the Linux kernel.



    The project SHOULD be buildable using only FLOSS tools. [build_floss_tools]

    All required tools are the same to build Linux, its obvious Linux can only be built by open source tools.


  • Automated test suite


    The project MUST use at least one automated test suite that is publicly released as FLOSS (this test suite may be maintained as a separate FLOSS project). The project MUST clearly show or document how to run the test suite(s) (e.g., via a continuous integration (CI) script or via documentation in files such as BUILD.md, README.md, or CONTRIBUTING.md). [test]

    Intel uses Linux backports for their own builds / release for users of 802.11 wifi. They have a series of run time tests against the 802.11 Intel wifi driver. This test the 802.11 subsystem and Intel's specific device driver against specific kernels.

    Its not okay to not have a generic run time automation test suite, this however is a bit complex though as it would mean testing at run time Linux backports builds on each supported 24 kernels for each release. There is also the issue of needing emulated devices to load and test drivers. This is a major undertaking. Some form of automating run time testing is desirable. As it stands we rely on independent stakeholders to do their own run time testing of supported device drivers. The rest of the drivers are supported as best effort.



    A test suite SHOULD be invocable in a standard way for that language. [test_invocation]


    It is SUGGESTED that the test suite cover most (or ideally all) the code branches, input fields, and functionality. [test_most]

    We definitely cannot test all known functions provided. We will try to at least do as much testing as possible in the future, but this will be restricted to what drivers can be emulated, and to each stakeholder's interest in the project and its driver's users.



    It is SUGGESTED that the project implement continuous integration (where new or changed code is frequently integrated into a central code repository and automated tests are run on the result). [test_continuous_integration]

    The 0-day bot does testing of every commit before it is merged into the main repository.


  • New functionality testing


    The project MUST have a general policy (formal or not) that as major new functionality is added to the software produced by the project, tests of that functionality should be added to an automated test suite. [test_policy]


    The project MUST have evidence that the test_policy for adding tests has been adhered to in the most recent major changes to the software produced by the project. [tests_are_added]


    It is SUGGESTED that this policy on adding tests (see test_policy) be documented in the instructions for change proposals. [tests_documented_added]

    Not yet done.


  • Warning flags


    The project MUST enable one or more compiler warning flags, a "safe" language mode, or use a separate "linter" tool to look for code quality errors or common simple mistakes, if there is at least one FLOSS tool that can implement this criterion in the selected language. [warnings]

    Since Linux kernel code is used we match the same practice and use the same tools to help look for issues. The same build flags are also used. The kernel build process enables a lot of warning flags, and it also provides the tool 'sparse' to check for many other coding problems. And a full test suite of coccineele scripts is integrated into the kernel source tree itself.



    The project MUST address warnings. [warnings_fixed]


    It is SUGGESTED that projects be maximally strict with warnings in the software produced by the project, where practical. [warnings_strict]

    Where ever practical, all warnings are fixed.


  • Secure development knowledge


    The project MUST have at least one primary developer who knows how to design secure software. (See ‘details’ for the exact requirements.) [know_secure_design]


    At least one of the project's primary developers MUST know of common kinds of errors that lead to vulnerabilities in this kind of software, as well as at least one method to counter or mitigate each of them. [know_common_errors]

  • Use basic good cryptographic practices

    Note that some software does not need to use cryptographic mechanisms. If your project produces software that (1) includes, activates, or enables encryption functionality, and (2) might be released from the United States (US) to outside the US or to a non-US-citizen, you may be legally required to take a few extra steps. Typically this just involves sending an email. For more information, see the encryption section of Understanding Open Source Technology & US Export Controls.

    The software produced by the project MUST use, by default, only cryptographic protocols and algorithms that are publicly published and reviewed by experts (if cryptographic protocols and algorithms are used). [crypto_published]


    If the software produced by the project is an application or library, and its primary purpose is not to implement cryptography, then it SHOULD only call on software specifically designed to implement cryptographic functions; it SHOULD NOT re-implement its own. [crypto_call]


    All functionality in the software produced by the project that depends on cryptography MUST be implementable using FLOSS. [crypto_floss]


    The security mechanisms within the software produced by the project MUST use default keylengths that at least meet the NIST minimum requirements through the year 2030 (as stated in 2012). It MUST be possible to configure the software so that smaller keylengths are completely disabled. [crypto_keylength]


    The default security mechanisms within the software produced by the project MUST NOT depend on broken cryptographic algorithms (e.g., MD4, MD5, single DES, RC4, Dual_EC_DRBG), or use cipher modes that are inappropriate to the context, unless they are necessary to implement an interoperable protocol (where the protocol implemented is the most recent version of that standard broadly supported by the network ecosystem, that ecosystem requires the use of such an algorithm or mode, and that ecosystem does not offer any more secure alternative). The documentation MUST describe any relevant security risks and any known mitigations if these broken algorithms or modes are necessary for an interoperable protocol. [crypto_working]


    The default security mechanisms within the software produced by the project SHOULD NOT depend on cryptographic algorithms or modes with known serious weaknesses (e.g., the SHA-1 cryptographic hash algorithm or the CBC mode in SSH). [crypto_weaknesses]


    The security mechanisms within the software produced by the project SHOULD implement perfect forward secrecy for key agreement protocols so a session key derived from a set of long-term keys cannot be compromised if one of the long-term keys is compromised in the future. [crypto_pfs]


    If the software produced by the project causes the storing of passwords for authentication of external users, the passwords MUST be stored as iterated hashes with a per-user salt by using a key stretching (iterated) algorithm (e.g., Argon2id, Bcrypt, Scrypt, or PBKDF2). See also OWASP Password Storage Cheat Sheet. [crypto_password_storage]


    The security mechanisms within the software produced by the project MUST generate all cryptographic keys and nonces using a cryptographically secure random number generator, and MUST NOT do so using generators that are cryptographically insecure. [crypto_random]

  • Secured delivery against man-in-the-middle (MITM) attacks


    The project MUST use a delivery mechanism that counters MITM attacks. Using https or ssh+scp is acceptable. [delivery_mitm]


    A cryptographic hash (e.g., a sha1sum) MUST NOT be retrieved over http and used without checking for a cryptographic signature. [delivery_unsigned]

  • Publicly known vulnerabilities fixed


    There MUST be no unpatched vulnerabilities of medium or higher severity that have been publicly known for more than 60 days. [vulnerabilities_fixed_60_days]


    Projects SHOULD fix all critical vulnerabilities rapidly after they are reported. [vulnerabilities_critical_fixed]

  • Other security issues


    The public repositories MUST NOT leak a valid private credential (e.g., a working password or private key) that is intended to limit public access. [no_leaked_credentials]

  • Static code analysis


    At least one static code analysis tool (beyond compiler warnings and "safe" language modes) MUST be applied to any proposed major production release of the software before its release, if there is at least one FLOSS tool that implements this criterion in the selected language. [static_analysis]

    Warning: Requires lengthier justification.



    It is SUGGESTED that at least one of the static analysis tools used for the static_analysis criterion include rules or approaches to look for common vulnerabilities in the analyzed language or environment. [static_analysis_common_vulnerabilities]


    All medium and higher severity exploitable vulnerabilities discovered with static code analysis MUST be fixed in a timely way after they are confirmed. [static_analysis_fixed]


    It is SUGGESTED that static source code analysis occur on every commit or at least daily. [static_analysis_often]

  • Dynamic code analysis


    It is SUGGESTED that at least one dynamic analysis tool be applied to any proposed major production release of the software before its release. [dynamic_analysis]


    It is SUGGESTED that if the software produced by the project includes software written using a memory-unsafe language (e.g., C or C++), then at least one dynamic tool (e.g., a fuzzer or web application scanner) be routinely used in combination with a mechanism to detect memory safety problems such as buffer overwrites. If the project does not produce software written in a memory-unsafe language, choose "not applicable" (N/A). [dynamic_analysis_unsafe]


    It is SUGGESTED that the project use a configuration for at least some dynamic analysis (such as testing or fuzzing) which enables many assertions. In many cases these assertions should not be enabled in production builds. [dynamic_analysis_enable_assertions]


    All medium and higher severity exploitable vulnerabilities discovered with dynamic code analysis MUST be fixed in a timely way after they are confirmed. [dynamic_analysis_fixed]


This data is available under the Creative Commons Attribution version 3.0 license (CC-BY-3.0) per the terms of use. All are free to share and adapt the data, but must give appropriate credit. Please credit Luis Rodriguez and the OpenSSF Best Practices badge contributors.

Project badge entry owned by: Luis Rodriguez.
Entry created on 2016-05-04 16:39:37 UTC, last updated on 2016-05-19 15:28:55 UTC. Last lost passing badge on 2021-04-11 18:16:21 UTC. Last achieved passing badge on 2016-05-04 22:16:00 UTC.

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