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Today's Topics:
1. The Linux x86/x86_64 maintainers .. and a Microsoft engineer
(Stephen Loosley)
----------------------------------------------------------------------
Message: 1
Date: Thu, 16 Jan 2025 18:28:31 +1030
From: Stephen Loosley <[email protected]>
To: "link" <[email protected]>
Subject: [LINK] The Linux x86/x86_64 maintainers .. and a Microsoft
engineer
Message-ID: <[email protected]>
Content-Type: text/plain; charset="UTF-8"
Intel, AMD engineers rush to save Linux 6.13 after dodgy Microsoft code change
'Let's not do this again please'... days before release date
By Richard Speed. Tue 14 Jan 2025
https://www.theregister.com/2025/01/14/microsoft_linux_change_pulled/
Intel and AMD engineers have stepped in at the eleventh hour to deal with a
code contribution from a Microsoft developer that could have broken Linux 6.13
on some systems.
The change, made in the autumn, was a useful improvement at face value. It was
a modification to Linux x86_64 to use large read-only execute (ROX) pages for
caching executable pages. The theory was that the alteration would result in
increased performance.
However, the code caused problems on some setups and an urgent patch from
Intel's Peter Zijlstra was committed yesterday to disable it. The stable
release of the 6.13 kernel was due this coming weekend.
Zijlstra wrote: "The whole module_writable_address() nonsense made a giant mess
of alternative.c, not to mention it still contains bugs -- notable (sic) some
of the CFI variants crash and burn.
Control Flow Integrity (CFI) is an anti-malware technology aimed at preventing
attackers from redirecting the control flow of a program. The change can cause
issues on some CFI-enabled setups and reports have included Intel Alder
Lake-powered machines failing to resume from hibernation.
Zijlstra said the Microsoft engineer "has been working on patches to clean all
this up again, but given the current state of things, this stuff just isn't
ready. Disable for now, let's try again next cycle."
The offending source is still present, but won't be included in the upcoming
stable kernel build.
News:
* Absolute Linux has reached the end ? where to next?
* Linus Torvalds offers to build guitar effects pedal for kernel developer
* Google and Linux Foundation form Chromium love club
* Public developer spats put bcachefs at risk in Linux
AMD engineer Borislav Petkov noted that the Linux x86_64 maintainers had not
signed off on the change, commenting: "I just love it how this went in without
a single x86 maintainer Ack, it broke a bunch of things and then it is still
there instead of getting reverted. Let's not do this again please."
Microsoft is notable for dubious quality control standards regarding releases
of its flagship operating system, Windows. That one of its engineers should
drop some dodgy code into the Linux kernel is not hugely surprising, and the
unfortunate individual is not the first and will not be the last to do so,
regardless of their employer.
However, the processes that allowed it to remain in the build this close to
public release will be a concern. While it is amusing that engineers from both
Intel and AMD were involved in dealing with the issues arising from the
contribution of a Microsoft engineer, and the problem never reached the stable
release, it is concerning. Petkov will not be the only one wondering how the
change made it in without a review by the Linux x86/x86_64 maintainers. ?
--
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