Date: Fri, 11 Nov 2016 12:41:27 +0000 From: Mark Rutland <mark.rutland@....com> To: kernel-hardening@...ts.openwall.com Cc: Kees Cook <keescook@...omium.org>, Peter Zijlstra <peterz@...radead.org>, Greg KH <gregkh@...uxfoundation.org>, Will Deacon <will.deacon@....com>, Elena Reshetova <elena.reshetova@...el.com>, Arnd Bergmann <arnd@...db.de>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <h.peter.anvin@...el.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: Re: [RFC v4 PATCH 00/13] HARDENED_ATOMIC On Fri, Nov 11, 2016 at 01:29:21AM +0100, Colin Vidal wrote: > On Fri, 2016-11-11 at 00:57 +0100, Peter Zijlstra wrote: > > On Thu, Nov 10, 2016 at 03:15:44PM -0800, Kees Cook wrote: > > > On Thu, Nov 10, 2016 at 2:27 PM, Greg KH <gregkh@...uxfoundation.org> wrote: > > > > On Thu, Nov 10, 2016 at 10:13:10PM +0100, Peter Zijlstra wrote: > I wonder if we didn't make a confusion between naming and > specifications. I have thought about Kees idea and what you're saying: > > - The name "atomic_t" name didn't tell anything about if the variable > can wrap or not. It just tells there is no race condition on > concurrent access, nothing else, and users are well with that. OK > then, we don't modify atomic_t, it makes sense. > > - Hence, let's say a new type "refcount_t". It names exactly what we > try to protect in this patch set. A much more simpler interface than > atomic_t would be needed, and it protects on race condition and > overflows (precisely what is expected of a counter reference). Not > an opt-in solution, but it is much less invasive since we "just" > have to modify the kref implementation and some vfs reference > counters. > > That didn't tell us how actually implements refcount_t: reuse some > atomic_t code or not (it would be simpler anyways, since we don't have > to implement the whole atomic_t interface). Still, this is another > problem. > > Sounds better? Regardless of atomic_t semantics, a refcount_t would be far more obvious to developers than atomic_t and/or kref, and better documents the intent of code using it. We'd still see abuse of atomic_t (and so this won't solve the problems Kees mentioned), but even as something orthogonal I think that would make sense to have. Thanks, Mark.
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