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Windows 17035 Kernel ASLR/VA Isolation In Practice (like Linux KAISER). First screenshot shows how NtCreateFile is not mapped in the kernel region of the user CR3. Second screenshot shows how a 'shadow' kernel trap handler, is (has to be).pic.twitter.com/7PriLIJHe1
One of the interesting things about this new feature is that user-mode PTEs are now marked as "global", preventing their flushing from TLB on process switch. Presumably because the OS can now do more targeted manual flushing as well as use PCID/PASID.
Wasn't Kaiser shown to be ineffective and with a rather large cost to syscalls?
Source? :-)
Did not find the lwn article on Kaiser's inefficacy that I read, but I did find this: https://lwn.net/Articles/737940/ …
Well, I’m sure the perf costs (especially on modern hardware with PASID/PCID) will be weighed against the security benefits, and people that care about loopback perf can turn it off in the registry. Remember this is WIP so it may never ship.
Reasonable. Can't imagine Microsoft will ship it if the perf hit on syscalls is ~40%.
I could easily measure it but MS gets mad if I ruin features ahead of time. I do quite like this one though and have nothing to bitch about :)
cant wait to the OS be 50% slower!!
I thought ASLR has virtually no impact on performance?
We’re talking about dual page tables here :)
Oh...yes. right. i missed that point. Last time i looked closely at a windows kernel it had no ASLR and it put everything in only two possible ringX. So having ASLR (in 2017) at all is an improvement already.
KASLR was added in Vista and improved in Windows 10. Not sure what you mean about two possible RingX? There may be some vocabulary confusion here :)
Linus has merged the concept into the mainlinehttps://lwn.net/Articles/742404/ …
And it’s being backported to 4.14
Can you eventually publish blog about this? I don't understand on what this new feature are..
I will probably _eventually_ publish a blog post... sometime after mid-January :)
Ok thanks
Any idea if this is applied to AMD CPUs in Windows?
AMD CPUs are not affected. https://lkml.org/lkml/2017/12/27/2 …
They’re not affected by the security issue, but they will be affected performance wise if Microsoft has applied the ‘fix’ to all x86 processors (as Linux has currently done). There doesn’t appear to be any clear answer as to how Microsoft have handled it.
Apparently Linus applied a patch removing AMD64 from the "bad X86" box. Not sure if/when that'll be applied to 4.15 and below, yet alone Windows is doing it. https://www.phoronix.com/scan.php?page=news_item&px=Linux-Tip-Git-Disable-x86-PTI …
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