Suppressing SIGBUS signals

Posted Jun 26, 2021 9:06 UTC (Sat) by Bigos (subscriber, #96807)
Parent article: Suppressing SIGBUS signals

I understand the premise that given "bad applications" the compositor authors want a mechanism to protect themselves from wrong client behavior that is set up solely by the compositor. It means less work on the whole ecosystem. But that just puts more custom logic into the kernel for no other reason than "let the kernel deal with it".

I thought Wayland was an extensible protocol that would allow one to fix such API mistakes and have clients and servers adopt the change gradually. However, nothing like that has been done for 7 years it seems. When can we expect Wayland successor that fixes this, then?

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Suppressing SIGBUS signals

Posted Jun 26, 2021 11:00 UTC (Sat) by Wol (subscriber, #4433) [Link] (2 responses)

> I understand the premise that given "bad applications" the compositor authors want a mechanism to protect themselves from wrong client behavior that is set up solely by the compositor.

Except it's nothing to do with "wrong client behaviour". You could be running a perfect client and then I log in on the same computer, truncate a file you're using, and bring YOUR desktop crashing down because of what I'VE done.

That's a vulnerability to a malicious actor, and this is (presumably) intended to fix that vulnerability (not bug).

Cheers,
Wol

Suppressing SIGBUS signals

Posted Jun 26, 2021 14:45 UTC (Sat) by Bigos (subscriber, #96807) [Link]

What I meant is to fix all legitimate applications (doing a change in mesa might solve the majority of it) and then eventually require sealed memfds instead of supporting the mechanism that is, as you mentioned, prone to abuse.

However, it seems the ship has already sailed and no one wants to change the protocol to accommodate this safer way of passing buffers around. Which is sad.

Suppressing SIGBUS signals

Posted Jul 5, 2021 8:54 UTC (Mon) by immibis (subscriber, #105511) [Link]

I'm sure there are many ways to bring things down if you can arbitrarily truncate files I'm using.

Suppressing SIGBUS signals

Posted Jun 26, 2021 14:08 UTC (Sat) by re:fi.64 (subscriber, #132628) [Link]

Afaik this isn't really a solvable issue for any protocol without just not supporting sending these at all, which would be a performance hit.