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Date: Wed, 27 Feb 2019 11:03:42 +0000
From: "Reshetova, Elena" <elena.reshetova@...el.com>
To: Kees Cook <keescook@...omium.org>, "Perla, Enrico"
<enrico.perla@...el.com>
CC: Andy Lutomirski <luto@...capital.net>, Andy Lutomirski <luto@...nel.org>,
Jann Horn <jannh@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
"tglx@...utronix.de" <tglx@...utronix.de>, "mingo@...hat.com"
<mingo@...hat.com>, "bp@...en8.de" <bp@...en8.de>, "tytso@....edu"
<tytso@....edu>
Subject: RE: [RFC PATCH] x86/entry/64: randomize kernel stack offset upon
system call
> On Wed, Feb 20, 2019 at 2:53 PM Kees Cook <keescook@...omium.org> wrote:
> > BTW, the attack that inspired grsecurity's RANDKSTACK is described in
> > these slides (lots of steps, see slide 79):
> > https://www.slideshare.net/scovetta/stackjacking
>
> Sorry, as PaX Team reminded me, I misremembered this. RANDKSTACK
> already existed. It was STACKLEAK that was created in response to this
> particular attack. I still think this attack is worth understanding to
> see what hoops must be jumped through when dealing with stack
> randomization (and other defenses).
Yes, I actually went through a number of stack-based attacks, including above,
in order to understand what we are trying to protect against.
If you are interested, I wrote some notes here mainly for organizing my own
thoughts and understanding:
https://docs.google.com/document/d/1h1gRuZpOjVxaaDag-MxOrASka0OEBeApQOl8OK2GIVY/edit?usp=sharing
It also has references to slidedecks of relevant attacks.
I am going to update them now based on our good discussion here.
Anyhow, I am glad that we arrived to conclusion here and I know how to proceed.
So, I will start working on randomizing after pt_regs in direction that Andy outlined.
With regards to disabling iopl(), this is pretty separate thing. If anyone wants to run
with this and submit a patch, please go ahead, I can also do it a bit later (after a study of it
since I never used it before) if noone finds bandwidth in the meantime.
Best Regards,
Elena.
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