Date: Fri, 10 Nov 2017 14:04:13 -0800 From: Andy Lutomirski <luto@...nel.org> To: "Hector Martin 'marcan'" <marcan@...can.st> Cc: LKML <linux-kernel@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, X86 ML <x86@...nel.org> Subject: Re: Re: vDSO maximum stack usage, stack probes, and -fstack-check > On Nov 10, 2017, at 8:36 AM, Hector Martin 'marcan' <marcan@...can.st> wrote: > >> On 2017-11-11 01:02, Hector Martin 'marcan' wrote: >> Not entirely sure what's going on here. > > Actually, if you think about it, it doesn't matter that it skips the > first page, since it's probing one page more. That just means the caller > will have probed the previous page. So ultimately you're just probing > ahead of where you need to, but that should be OK. > The whole point is to touch the stack pages in order. Also, I see no guarantee that the function would touch the intermediate page before clobbering the probed page. You're seeing exactly that behavior, in fact. > -- > Hector Martin "marcan" (marcan@...can.st) > Public Key: https://mrcn.st/pub
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