<meta http-equiv="refresh" content="0; URL=https://mobile.twitter.com/i/nojs_router?path=%2Faionescu%2Fstatus%2F930412525111296000"> (cache)Alex Ionescu on Twitter: "Windows 17035 Kernel ASLR/VA Isolation In Practice (like Linux KAISER). First screenshot shows how NtCreateFile is not mapped in the kernel… https://t.co/QPVeH5cdBl"

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aionescu's profile
Alex Ionescu
Alex Ionescu
Alex Ionescu
@aionescu

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Alex Ionescu

@aionescu

Windows Internals Expert, Security Ninja, and Embedded ARM Kernel Guru.

Seattle, WA
alex-ionescu.com
Joined April 2008

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    Alex Ionescu‏ @aionescu 14 Nov 2017

    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

    4:30 AM - 14 Nov 2017
    • 212 Retweets
    • 381 Likes
    • Evan Pitstick Ratul Gupta Artem Pronichkin Sergej Schumilo Kath Idan Freiberg Joshua Barretto Chris McKee Ze CyberCynic
    15 replies 212 retweets 381 likes
      1. Alex Ionescu‏ @aionescu 16 Nov 2017

        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.

        1 reply 6 retweets 24 likes
        Show this thread
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      1. New conversation
      2. Aaron Friel‏ @AaronFriel 14 Nov 2017
        Replying to @aionescu

        Wasn't Kaiser shown to be ineffective and with a rather large cost to syscalls?

        1 reply 1 retweet 1 like
      3. Alex Ionescu‏ @aionescu 14 Nov 2017
        Replying to @AaronFriel

        Source? :-)

        1 reply 1 retweet 2 likes
      4. Aaron Friel‏ @AaronFriel 14 Nov 2017
        Replying to @aionescu

        Did not find the lwn article on Kaiser's inefficacy that I read, but I did find this: https://lwn.net/Articles/737940/ …

        1 reply 2 retweets 5 likes
      5. Alex Ionescu‏ @aionescu 14 Nov 2017
        Replying to @AaronFriel

        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.

        4 replies 0 retweets 10 likes
      6. Aaron Friel‏ @AaronFriel 14 Nov 2017
        Replying to @aionescu

        Reasonable. Can't imagine Microsoft will ship it if the perf hit on syscalls is ~40%.

        2 replies 0 retweets 2 likes
      7. Alex Ionescu‏ @aionescu 14 Nov 2017
        Replying to @AaronFriel

        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 :)

        1 reply 0 retweets 13 likes
      8. Tweet unavailable
      9. Alex Ionescu‏ @aionescu 14 Nov 2017

        Fonts are now userspace and appcontainerized. Shit is getting real/hard/real hard.

        1 reply 1 retweet 16 likes
      10. 1 more reply
      1. New conversation
      2. Wikinger‏ @wikinger7 14 Nov 2017
        Replying to @aionescu

        cant wait to the OS be 50% slower!!

        1 reply 0 retweets 4 likes
      3. Eliannuminas‏ @Eliannuminas 15 Nov 2017
        Replying to @wikinger7 @aionescu

        I thought ASLR has virtually no impact on performance?

        1 reply 0 retweets 0 likes
      4. Alex Ionescu‏ @aionescu 15 Nov 2017
        Replying to @Eliannuminas @wikinger7

        We’re talking about dual page tables here :)

        1 reply 0 retweets 1 like
      5. Eliannuminas‏ @Eliannuminas 15 Nov 2017
        Replying to @aionescu @wikinger7

        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.

        1 reply 0 retweets 0 likes
      6. Alex Ionescu‏ @aionescu 15 Nov 2017
        Replying to @Eliannuminas @wikinger7

        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 :)

        0 replies 0 retweets 4 likes
      7. End of conversation
      1. New conversation
      2. Saar Amar‏ @AmarSaar Jan 1
        Replying to @aionescu

        Linus has merged the concept into the mainlinehttps://lwn.net/Articles/742404/ …

        2 replies 2 retweets 8 likes
      3. Alex Ionescu‏ @aionescu Jan 1
        Replying to @AmarSaar

        And it’s being backported to 4.14

        1 reply 0 retweets 8 likes
      4. Aaron Friel‏ @AaronFriel Jan 3
        Replying to @aionescu @AmarSaar

        It'll be cherry picked into LTS kernels for major vendors, there's no way it remains 4.14+.

        0 replies 0 retweets 1 like
      5. End of conversation
      1. New conversation
      2. vaualbus‏ @AlbertoVaudagna 16 Nov 2017
        Replying to @aionescu

        Can you eventually publish blog about​ this? I don't understand on what this new feature are..

        1 reply 0 retweets 1 like
      3. Alex Ionescu‏ @aionescu Jan 1
        Replying to @AlbertoVaudagna

        I will probably _eventually_ publish a blog post... sometime after mid-January :)

        1 reply 1 retweet 13 likes
      4. vaualbus‏ @AlbertoVaudagna Jan 1
        Replying to @aionescu

        Ok thanks

        0 replies 0 retweets 1 like
      5. End of conversation

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