From: "Reshetova, Elena" <elena.reshetova@intel.com>
To: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>,
Kernel Hardening <kernel-hardening@lists.openwall.com>,
Andy Lutomirski <luto@amacapital.net>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Jann Horn <jannh@google.com>,
"Perla, Enrico" <enrico.perla@intel.com>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Greg KH <gregkh@linuxfoundation.org>
Subject: RE: [RFC PATCH] x86/entry/64: randomize kernel stack offset upon syscall
Date: Fri, 5 Apr 2019 10:14:45 +0000 [thread overview]
Message-ID: <2236FBA76BA1254E88B949DDB74E612BA4C40185@IRSMSX102.ger.corp.intel.com> (raw)
In-Reply-To: <CAGXu5j+05tZUOuka2YQy+5WPvVwHBrM-YEeto1iLzz2shCnANQ@mail.gmail.com>
> On Thu, Apr 4, 2019 at 4:41 AM Reshetova, Elena
> <elena.reshetova@intel.com> wrote:
> > What I still don't fully understand here (due to my little knowledge of
> > compilers) and afraid of is that the asm code that alloca generates (see my version)
> > and the alignment might differ on the different targets, etc.
>
> I guess it's possible, but for x86_64, since appears to be consistent.
So, yes, I double checked this now with just printing all possible offsets I get for rsp
from do_syscall_64, it is indeed 33 different offsets, so it is indeed more like 5 bits of entropy.
We can increase it, if we want and people are ok with losing a bit more stack space.
>
> > If you tried it on yours, can you send me the asm code that it produced for you?
> > Is it different from mine?
>
> You can compare compiler outputs here. Here's gcc vs clang for this code:
> https://godbolt.org/z/WJSbN8
> You can adjust compiler versions, etc.
Oh, this is handy! Thank you for the link!
So, should I resend to lkml (with some cosmetic fixes) or how to proceed with this?
I will also update the randomness bit info.
Best Regards,
Elena.
next prev parent reply other threads:[~2019-04-05 10:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-29 8:13 [RFC PATCH] x86/entry/64: randomize kernel stack offset upon syscall Elena Reshetova
2019-04-03 21:17 ` Kees Cook
2019-04-04 11:41 ` Reshetova, Elena
2019-04-04 17:03 ` Kees Cook
2019-04-05 10:14 ` Reshetova, Elena [this message]
2019-04-05 13:14 ` Andy Lutomirski
-- strict thread matches above, loose matches on Subject: below --
2019-03-20 7:27 Elena Reshetova
2019-03-20 7:29 ` Reshetova, Elena
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