From: "PaX Team" <pageexec@freemail.hu>
To: Kees Cook <keescook@chromium.org>, Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, Eric Biggers <ebiggers3@gmail.com>,
Christoph Hellwig <hch@infradead.org>,
"axboe@kernel.dk" <axboe@kernel.dk>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
Elena Reshetova <elena.reshetova@intel.com>,
Hans Liljestrand <ishkamiel@gmail.com>,
David Windsor <dwindsor@gmail.com>,
x86@kernel.org, Ingo Molnar <mingo@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jann Horn <jann@thejh.net>,
davem@davemloft.net, linux-arch@vger.kernel.org,
kernel-hardening@lists.openwall.com
Subject: Re: [PATCH] x86/refcount: Implement fast refcount_t handling
Date: Tue, 25 Apr 2017 13:26:43 +0200 [thread overview]
Message-ID: <58FF3273.5306.1C99E565@pageexec.freemail.hu> (raw)
In-Reply-To: <20170425102337.ocdi2v7ivue7x7cc@hirez.programming.kicks-ass.net>
On 25 Apr 2017 at 12:23, Peter Zijlstra wrote:
> So what avoids this:
simple, you noted it yourself in your previous mail:
> Well, your setup (panic_on_warn et al) would have it panic the box. That
> will effectively stop the exploit by virtue of stopping everything.
with that in mind the actual code looks like this:
> CPU0 CPU1
>
>
> lock inc %[val]; # 0x7fffffff
> jo 2f
>1: ...
>
> lock dec %[val]; # 0x80000000
> jo 2f
> 1: ...
>
>
>
>
>2: mov $0x7fffffff, %[val]
panic()
> jmp 1b
>
> 2: mov $0x80000000, %[val]
panic()
> jmp 1b
>
... and we never get this far.
prev parent reply other threads:[~2017-04-25 11:28 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-21 22:09 Kees Cook
2017-04-24 8:32 ` Peter Zijlstra
2017-04-24 8:53 ` [kernel-hardening] " Jann Horn
2017-04-24 9:20 ` Peter Zijlstra
2017-04-24 11:00 ` PaX Team
2017-04-24 11:15 ` Peter Zijlstra
2017-04-24 13:08 ` PaX Team
2017-04-24 13:33 ` Peter Zijlstra
2017-04-24 15:15 ` PaX Team
2017-04-24 20:40 ` Kees Cook
2017-04-24 22:01 ` Peter Zijlstra
2017-04-24 22:37 ` Kees Cook
2017-04-25 1:11 ` [kernel-hardening] " Rik van Riel
2017-04-25 9:05 ` Peter Zijlstra
2017-04-25 11:26 ` PaX Team
2017-04-25 16:36 ` Kees Cook
2017-04-24 20:33 ` Kees Cook
2017-04-25 11:26 ` PaX Team
2017-04-25 16:39 ` Kees Cook
2017-04-26 2:14 ` PaX Team
2017-04-26 4:42 ` Kees Cook
2017-04-24 20:16 ` Kees Cook
2017-04-24 10:45 ` Peter Zijlstra
2017-04-24 20:19 ` Kees Cook
2017-04-24 10:48 ` Peter Zijlstra
2017-04-24 20:21 ` Kees Cook
2017-04-25 10:23 ` Peter Zijlstra
2017-04-25 11:26 ` PaX Team [this message]
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