kernel-hardening - Re: [PATCH v5 0/3] Implement fast refcount overflow protection

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Message-ID: <20170531122732.GA24923@linux-80c1.suse>
Date: Wed, 31 May 2017 05:27:32 -0700
From: Davidlohr Bueso <dave@...olabs.net>
To: Kees Cook <keescook@...omium.org>
Cc: linux-kernel@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
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	Hans Liljestrand <ishkamiel@...il.com>,
	David Windsor <dwindsor@...il.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
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	"x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...nel.org>,
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	Rik van Riel <riel@...hat.com>,
	linux-arch <linux-arch@...r.kernel.org>,
	"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v5 0/3] Implement fast refcount overflow protection

On Tue, 30 May 2017, Kees Cook wrote:

>A new patch has been added at the start of this series to make the default
>refcount_t implementation just use an unchecked atomic_t implementation,
>since many kernel subsystems want to be able to opt out of the full
>validation, since it includes a small performance overhead. When enabling
>CONFIG_REFCOUNT_FULL, the full validation is used.
>
>The other two patches provide overflow protection on x86 without incurring
>a performance penalty. The changelog for patch 3 is reproduced here for
>details:

To be sure I'm getting this right, after this all archs with the exception
of x86 will use the regular atomic_t ("unsecure") flavor, right?

Thanks,
Davidlohr

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