Date: Tue, 25 Apr 2017 11:05:58 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Kees Cook <keescook@...omium.org> Cc: PaX Team <pageexec@...email.hu>, LKML <linux-kernel@...r.kernel.org>, Eric Biggers <ebiggers3@...il.com>, Christoph Hellwig <hch@...radead.org>, "axboe@...nel.dk" <axboe@...nel.dk>, James Bottomley <James.Bottomley@...senpartnership.com>, Elena Reshetova <elena.reshetova@...el.com>, Hans Liljestrand <ishkamiel@...il.com>, David Windsor <dwindsor@...il.com>, "x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...nel.org>, Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jann Horn <jann@...jh.net>, "David S. Miller" <davem@...emloft.net>, linux-arch <linux-arch@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH] x86/refcount: Implement fast refcount_t handling On Mon, Apr 24, 2017 at 03:37:32PM -0700, Kees Cook wrote: > On Mon, Apr 24, 2017 at 3:01 PM, Peter Zijlstra <peterz@...radead.org> wrote: > > It does not. It just got free'ed. Nothing will stop the free from > > happening (or already having happened). > > Well, yes, but that's kind of my point. Detecting inc-from-0 is "too > late" to offer a protection. It offers notification of a bug, rather > than stopping an exploit from happening. 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. And warn/bug/panic etc.. are I think a better option that silently letting it happen.
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