Date: Mon, 29 May 2017 01:39:04 -0700 From: Christoph Hellwig <hch@...radead.org> To: Kees Cook <keescook@...omium.org> Cc: Andrew Morton <akpm@...ux-foundation.org>, Elena Reshetova <elena.reshetova@...el.com>, Peter Zijlstra <peterz@...radead.org>, Greg KH <gregkh@...uxfoundation.org>, "Eric W. Biederman" <ebiederm@...ssion.com>, Ingo Molnar <mingo@...hat.com>, Alexey Dobriyan <adobriyan@...il.com>, "Serge E. Hallyn" <serge@...lyn.com>, arozansk@...hat.com, Davidlohr Bueso <dave@...olabs.net>, Manfred Spraul <manfred@...orfullife.com>, Christoph Hellwig <hch@...radead.org>, "axboe@...nel.dk" <axboe@...nel.dk>, James Bottomley <James.Bottomley@...senpartnership.com>, "x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...nel.org>, Arnd Bergmann <arnd@...db.de>, "David S. Miller" <davem@...emloft.net>, Rik van Riel <riel@...hat.com>, linux-arch <linux-arch@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 0/3] ipc subsystem refcounter conversions 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.
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