From: Kees Cook <keescook@chromium.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Andrew Morton <akpm@linux-foundation.org>,
Jann Horn <jannh@google.com>, Eric Biggers <ebiggers3@gmail.com>,
Elena Reshetova <elena.reshetova@intel.com>,
Hans Liljestrand <ishkamiel@gmail.com>,
Greg KH <gregkh@linuxfoundation.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
"Serge E. Hallyn" <serge@hallyn.com>,
arozansk@redhat.com, Davidlohr Bueso <dave@stgolabs.net>,
Manfred Spraul <manfred@colorfullife.com>,
"axboe@kernel.dk" <axboe@kernel.dk>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
"x86@kernel.org" <x86@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
"David S. Miller" <davem@davemloft.net>,
Rik van Riel <riel@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection
Date: Thu, 20 Jul 2017 10:15:33 -0700 [thread overview]
Message-ID: <CAGXu5jK0t0Xfj1oTUg51USEaJ7je+KMNoE0irfYNon2aAmhg7g@mail.gmail.com> (raw)
In-Reply-To: <20170720091106.kigtr6zy7pjgk2s6@gmail.com>
On Thu, Jul 20, 2017 at 2:11 AM, Ingo Molnar <mingo@kernel.org> wrote:
> Could you please also create a tabulated quick-comparison of the three variants,
> of all key properties, about behavior, feature and tradeoff differences?
>
> Something like:
>
> !ARCH_HAS_REFCOUNT ARCH_HAS_REFCOUNT=y REFCOUNT_FULL=y
>
> avg fast path instructions: 5 3 10
> behavior on overflow: unsafe, silent safe, verbose safe, verbose
> behavior on underflow: unsafe, silent unsafe, verbose unsafe, verbose
> ...
>
> etc. - note that this table is just a quick mockup with wild guesses. (Please add
> more comparisons of other aspects as well.)
>
> Such a comparison would make it easier for arch, subsystem and distribution
> maintainers to decide on which variant to use/enable.
Sure, I can write this up. I'm not sure "safe"/"unsafe" is quite that
clean. The differences between -full and -fast are pretty subtle, but
I think I can describe it using the updated LKDTM tests I've written
to compare the two. There are conditions that -fast doesn't catch, but
those cases aren't actually useful for the overflow defense.
As for "avg fast path instructions", do you mean the resulting
assembly for each refcount API function? I think it's going to look
something like "1 2 45", but I'll write it up.
-Kees
--
Kees Cook
Pixel Security
next prev parent reply other threads:[~2017-07-20 17:15 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-19 0:03 [PATCH v6 0/2] x86: Implement fast refcount overflow protection Kees Cook
2017-07-19 0:03 ` [PATCH v6 1/2] x86/asm: Add suffix macro for GEN_*_RMWcc() Kees Cook
2017-07-19 0:03 ` [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow protection Kees Cook
2017-07-19 19:37 ` Josh Poimboeuf
2017-07-19 19:45 ` Kees Cook
2017-07-19 19:52 ` Josh Poimboeuf
2017-07-19 22:50 ` Kees Cook
2017-07-19 23:01 ` Josh Poimboeuf
2017-07-19 23:12 ` Kees Cook
2017-07-19 23:30 ` Josh Poimboeuf
2017-07-20 9:11 ` [PATCH v6 0/2] x86: " Ingo Molnar
2017-07-20 17:15 ` Kees Cook [this message]
2017-07-20 22:53 ` Kees Cook
2017-07-21 7:50 ` Ingo Molnar
2017-07-21 21:22 ` Andrew Morton
2017-07-22 3:33 ` Kees Cook
2017-07-24 6:38 ` Michael Ellerman
2017-07-24 8:44 ` Peter Zijlstra
2017-07-24 12:09 ` Michael Ellerman
2017-07-24 12:23 ` Peter Zijlstra
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