KAISER: hiding the kernel from user space [LWN.net]

KAISER: hiding the kernel from user space

Posted Nov 17, 2017 17:45 UTC (Fri) by valarauca (guest, #109490)
Parent article: KAISER: hiding the kernel from user space

Timing attacks are becoming the bane of x64.

AVX512 adds explicit flags to suppress memory errors on scatter/gather load/store vectorized instructions which will just add another method to exploit this. The ways of _accessing_ memory you can't access on x64 just continue to grow. I really don't see how AMD64 can fix this without breaking either the page table or the debug timers.

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KAISER: hiding the kernel from user space

Posted Nov 18, 2017 0:09 UTC (Sat) by anton (subscriber, #25547) [Link] (1 responses)

I read some performance caveats about vmaskmovps (AVX, not sure if there is an SSE equivalent) that make me think that this instruction can be used for such purposes, too.

Concerning the article, hyperbole is the standard in security news, but "a hardened kernel is no longer optional" seems to be a little extreme even so. I very much hope that stuff like this will be optional.

A possibly less costly way to mitigate attacks that try to defeat KASLR might be to map additional inaccessible address space that would respond to the attacks just like real kernel memory.

wordage nuance

Posted Nov 30, 2017 1:32 UTC (Thu) by Garak (guest, #99377) [Link]

Concerning the article, hyperbole is the standard in security news, but "a hardened kernel is no longer optional" seems to be a little extreme even so. I very much hope that stuff like this will be optional.

My reaction for a couple seconds as well till I read the next sentence. I agree that sentence is not the best way to describe things. I think it's important to highlight that security-vs-performance tradeoffs is a vast spectrum of subtle choices that *depend on the situation/deployment*. There are many different situations. Quite often a performance hit from enabling SELinux or whatever new hardening-with-five-percent-hit tactic, is absolutely not worth it. Other times your computers are trying to secure millions of dollars of cryptocurrency/etc. Most users should be taught about such nuance versus the "more secure equals always better" narrative. If something is useful to lots of people, sure it should be available as an option. But leave it to the distributors and then the end users to figure out when and where various options should be tuned.