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Hutterer: X servers no longer allow byte-swapped clients

 2 years ago
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Hutterer: X servers no longer allow byte-swapped clients

[Posted January 6, 2023 by corbet]
Peter Hutterer writes about the disabling of support for byte-swapped clients in the X.org server and the reasons why this was done.
These days, encountering a Big Endian host is increasingly niche, letting it run an X client that connects to your local little-endian X server is even more niche. I think the only regular real-world use-case for this is running X clients on an s390x, connecting to your local intel-ish (and thus little endian) workstation. Not something most users do on a regular basis. So right now, the byte-swapping code is mainly a free attack surface that 99% of users never actually use for anything real. So... let's not do that?
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Hutterer: X servers no longer allow byte-swapped clients

Posted Jan 6, 2023 14:35 UTC (Fri) by dullfire (subscriber, #111432) [Link]

> I think the only regular real-world use-case for this is running X clients on an s390x, connecting to your local intel-ish (and thus little endian) workstation.

I know there are several distros out there that use/can-use BE, Adelie for one. I use gentoo in BE on my P9, and since my P9 is normally headless X11 forwarding from is is the norm for me. I think this use case is probably a bit less nitch that Peter believes it is.

Hutterer: X servers no longer allow byte-swapped clients

Posted Jan 6, 2023 14:46 UTC (Fri) by saffroy (guest, #43999) [Link]

With "P9" do you mean a POWER9 machine, or something completely different?

Hutterer: X servers no longer allow byte-swapped clients

Posted Jan 6, 2023 14:50 UTC (Fri) by dullfire (subscriber, #111432) [Link]

Yeah I should have clarified. I do mean a POWER9.

Hutterer: X servers no longer allow byte-swapped clients

Posted Jan 6, 2023 15:56 UTC (Fri) by Sesse (subscriber, #53779) [Link]

Running big-endian Gentoo on a headless POWER9 with X forwarding is not niche for you? :-)

Hutterer: X servers no longer allow byte-swapped clients

Posted Jan 6, 2023 16:07 UTC (Fri) by dullfire (subscriber, #111432) [Link]

> Running big-endian Gentoo on a headless POWER9 with X forwarding is not niche for you? :-)

That's a misreading of what I said. I gave a quote that seems to indicate Peter believes the only real-world use case is in conjunction with s390 systems. I gave a counter example. And further explained that there are distros (like Adelie, and BE PPC64 gentoo) that this could effect. Is it at all niche? Certainly. Is it as niche as Peter seems to suggest? Almost certainly not (and I would consider the difference between "only certain cases of s390 systems" and "PPC64/Adelie, BE gentoo, s390, +others" to be a significant difference, even if both are "niche").

Hutterer: X servers no longer allow byte-swapped clients

Posted Jan 6, 2023 18:31 UTC (Fri) by clump (subscriber, #27801) [Link]

I've run Linux on at least six architectures that I can recall. I very much felt the rough edges when there are few users and precious fewer developers. I couldn't imagine realistic support of any kind for non-x86 architectures outside of enterprise distributions.

Hutterer: X servers no longer allow byte-swapped clients

Posted Jan 6, 2023 15:31 UTC (Fri) by dskoll (subscriber, #1630) [Link]

According to the article, it's only disabled by default and can be re-enabled with a command-line option. So a good decision IMO.

Hutterer: X servers no longer allow byte-swapped clients

Posted Jan 6, 2023 15:32 UTC (Fri) by higuita (guest, #32245) [Link]

Correct, and you can also fallback to vnc or other virtual desktop tool

Hutterer: X servers no longer allow byte-swapped clients

Posted Jan 6, 2023 17:25 UTC (Fri) by jreiser (subscriber, #11027) [Link]

> it's only disabled by default and can be re-enabled with a command-line option

Finding and changing the invocation of the X server can be a chore because common desktop environments do not expose it. It may be necessary to wrap the executable file in a shell script which massages argv[].

Niches are for dogs.

Posted Jan 6, 2023 20:52 UTC (Fri) by ballombe (subscriber, #9523) [Link]

Everything I do with linux can be considered niche. I assume all will become unsupported in the name of security. Somehow I do not think I will be safer.

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