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From: Christoph Hellwig <hch@infradead.org>
To: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Elena Reshetova <elena.reshetova@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Ingo Molnar <mingo@redhat.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	arozansk@redhat.com, Davidlohr Bueso <dave@stgolabs.net>,
	Manfred Spraul <manfred@colorfullife.com>,
	Christoph Hellwig <hch@infradead.org>,
	"axboe@kernel.dk" <axboe@kernel.dk>,
	James Bottomley <James.Bottomley@hansenpartnership.com>,
	"x86@kernel.org" <x86@kernel.org>, Ingo Molnar <mingo@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
	"David S. Miller" <davem@davemloft.net>,
	Rik van Riel <riel@redhat.com>,
	linux-arch <linux-arch@vger.kernel.o>
Subject: Re: [PATCH 0/3] ipc subsystem refcounter conversions
Date: Mon, 29 May 2017 01:39:04 -0700	[thread overview]
Message-ID: <20170529083903.GA17735@infradead.org> (raw)
In-Reply-To: <CAGXu5jKNChaVdfbM171FYkvY1hUMXG6cp-=WAdXBP0eTOO5RAA@mail.gmail.com>

On Sat, May 27, 2017 at 12:58:14PM -0700, Kees Cook wrote:
> FAST_REFCOUNT=n: use function-based refcount_t with cmpxvhg and
> full-verification
> FAST_REFCOUNT=y without arch-specific implementation: use atomic_t
> with no verification (i.e. no functional change from now)
> FAST_REFCOUNT=y with arch-specific implementation: use atomic_t with
> overflow protection
> 
> which means FAST_REFCOUNT would need to be default-on so that mm,
> block, net users will remain happy.
> 
> Does that sound reasonable?

I'd rather turn the options around so that the atomic_t or fast
arch implementations are the defaul.  But either way it needs to
be configurable.  Once that is done we can spread refcount_t everywhere
and everyone will be better off, if only for the documentation value
of the type when they use the atomic_t based implementation.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Elena Reshetova <elena.reshetova@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Ingo Molnar <mingo@redhat.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	arozansk@redhat.com, Davidlohr Bueso <dave@stgolabs.net>,
	Manfred Spraul <manfred@colorfullife.com>,
	Christoph Hellwig <hch@infradead.org>,
	"axboe@kernel.dk" <axboe@kernel.dk>,
	James Bottomley <James.Bottomley@hansenpartnership.com>,
	"x86@kernel.org" <x86@kernel.org>, Ingo Molnar <mingo@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
	"David S. Miller" <davem@davemloft.net>,
	Rik van Riel <riel@redhat.com>,
	linux-arch <linux-arch@vger.kernel.org>,
	"kernel-hardening@lists.openwall.com"
	<kernel-hardening@lists.openwall.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/3] ipc subsystem refcounter conversions
Date: Mon, 29 May 2017 01:39:04 -0700	[thread overview]
Message-ID: <20170529083903.GA17735@infradead.org> (raw)
Message-ID: <20170529083904.Tca6sWwcBeZbdSI_omMalQXiSXAoZLxod-c96OFV0n8@z> (raw)
In-Reply-To: <CAGXu5jKNChaVdfbM171FYkvY1hUMXG6cp-=WAdXBP0eTOO5RAA@mail.gmail.com>

On Sat, May 27, 2017 at 12:58:14PM -0700, Kees Cook wrote:
> FAST_REFCOUNT=n: use function-based refcount_t with cmpxvhg and
> full-verification
> FAST_REFCOUNT=y without arch-specific implementation: use atomic_t
> with no verification (i.e. no functional change from now)
> FAST_REFCOUNT=y with arch-specific implementation: use atomic_t with
> overflow protection
> 
> which means FAST_REFCOUNT would need to be default-on so that mm,
> block, net users will remain happy.
> 
> Does that sound reasonable?

I'd rather turn the options around so that the atomic_t or fast
arch implementations are the defaul.  But either way it needs to
be configurable.  Once that is done we can spread refcount_t everywhere
and everyone will be better off, if only for the documentation value
of the type when they use the atomic_t based implementation.

  parent reply	other threads:[~2017-05-29  8:39 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1487590189-18151-1-git-send-email-elena.reshetova@intel.com>
     [not found] ` <20170303162352.b6af1c0c3115b3f5f1e7aed3@linux-foundation.org>
2017-05-27 19:58   ` [PATCH 0/3] ipc subsystem refcounter conversions Kees Cook
2017-05-27 19:58     ` Kees Cook
2017-05-29  8:39     ` Christoph Hellwig [this message]
2017-05-29  8:39       ` Christoph Hellwig
2017-05-29  9:11       ` Eric W. Biederman
2017-05-29  9:11         ` Eric W. Biederman
2017-05-29 10:24         ` Peter Zijlstra
2017-05-29 10:24           ` Peter Zijlstra
2017-05-29 10:49           ` Eric W. Biederman
2017-05-29 10:49             ` Eric W. Biederman
2017-05-29 11:30             ` Eric W. Biederman
2017-05-29 11:30               ` Eric W. Biederman
2017-05-29 11:39               ` Eric W. Biederman
2017-05-29 11:39                 ` Eric W. Biederman
2017-05-29 12:23                 ` Peter Zijlstra
2017-05-29 12:23                   ` Peter Zijlstra
2017-05-29 15:43                   ` Peter Zijlstra
2017-05-29 15:43                     ` Peter Zijlstra
2017-05-29 12:13             ` Peter Zijlstra
2017-05-29 12:13               ` Peter Zijlstra

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