linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Andy Lutomirski <luto@kernel.org>
To: "Hector Martin 'marcan'" <marcan@marcan.st>
Cc: LKML <linux-kernel@vger.kernel.org>,
	"kernel-hardening@lists.openwall.com" 
	<kernel-hardening@lists.openwall.com>, X86 ML <x86@kernel.org>
Subject: Re: [kernel-hardening] Re: vDSO maximum stack usage, stack probes, and -fstack-check
Date: Fri, 10 Nov 2017 14:04:13 -0800	[thread overview]
Message-ID: <CALCETrVd-f-N=O6QmtdzS7oSVkXpsJhxH+=9+0fvfFmy5Cz3WQ@mail.gmail.com> (raw)
In-Reply-To: <a4f2bc2f-4d90-85fe-c0cc-d0d31551e933@marcan.st>

> On Nov 10, 2017, at 8:36 AM, Hector Martin 'marcan' <marcan@marcan.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@marcan.st)
> Public Key: https://mrcn.st/pub

  reply	other threads:[~2017-11-10 22:04 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-10 10:40 vDSO maximum stack usage, stack probes, and -fstack-check Hector Martin 'marcan'
2017-11-10 14:57 ` Andy Lutomirski
2017-11-10 16:02   ` [kernel-hardening] " Hector Martin 'marcan'
2017-11-10 16:36     ` Hector Martin 'marcan'
2017-11-10 22:04       ` Andy Lutomirski [this message]
2017-11-11  5:16         ` Hector Martin 'marcan'
2017-11-12  4:21           ` Andy Lutomirski
2017-11-12  4:39             ` Hector Martin 'marcan'
2017-11-10 22:04     ` Andy Lutomirski

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CALCETrVd-f-N=O6QmtdzS7oSVkXpsJhxH+=9+0fvfFmy5Cz3WQ@mail.gmail.com' \
    --to=luto@kernel.org \
    --cc=kernel-hardening@lists.openwall.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=marcan@marcan.st \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).