Microsoft change removed from Linux over Intel CPU issues
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.
Update
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Microsoft pulls a Windows as it breaks Linux on Intel CPUs and angers AMD in the process
Earlier today, we reported about a happy and content Linus Torvalds, who is offering to make a guitar pedal for one of the lucky Linux devs out there since he is pleased with how things have been this holiday season and the progress with the Linux kernel version 6.13.
Unfortunately for Torvalds, a Microsoft-contributed change nearly ruined it, but Intel and AMD had intervened just in time to save the day.
The change in question was related to a ARCH_HAS_EXECMEM_ROX kernel configuration, which would allow caching of executable memory (EXECMEM) with read-only execute (ROX) permissions. It was being added as a performance improvement feature on Linux 6.13 for x86_64/ AMD64, ie, 64-bit AMD and Intel CPUs.
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Microsoft Breaks Linux Again