From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: castet.matthieu@free.fr
Cc: linux-kernel@vger.kernel.org
Subject: Re: Using x86 segments against NULL pointer deference exploit
Date: Fri, 6 Nov 2009 13:13:30 +0000 [thread overview]
Message-ID: <20091106131330.0ce956f4@lxorguk.ukuu.org.uk> (raw)
In-Reply-To: <1257512389.4af41dc504e1b@imp.free.fr>
On Fri, 06 Nov 2009 13:59:49 +0100
castet.matthieu@free.fr wrote:
> Hi,
>
> I am wondering why we can't set the KERNEL_DS data segment to not contain the
> first page, ie changing it from R/W flat model to R/W expand down from
> 0xffffffff to 4096.
For one it is enormously expensive because the moment you have segment
limits all sorts of stuff goes slower. You also do sometimes need low 4K
access for wine/dosemu etc as you guess - and for APM and so on. Plus in
64bit you don't have a lot of those features ayway.
> The drawback of this it that the kernel can't access anymore data in the first
> segment. Is it needed for application like wine or dosemu ?
Yes.
next prev parent reply other threads:[~2009-11-06 13:11 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-06 12:59 castet.matthieu
2009-11-06 13:13 ` Alan Cox [this message]
2009-11-06 20:35 ` matthieu castet
2009-11-09 6:30 ` H. Peter Anvin
2009-11-06 20:18 ` Andi Kleen
2009-11-08 14:38 ` matthieu castet
2009-11-08 19:41 ` Andi Kleen
2009-11-06 20:58 ` Jiri Kosina
2009-11-06 22:54 ` H. Peter Anvin
2009-11-07 10:20 ` Jiri Kosina
[not found] <dDwJH-3PE-7@gated-at.bofh.it>
2009-11-10 16:46 ` Markku Savela
2009-11-11 14:11 ` Jiri Kosina
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=20091106131330.0ce956f4@lxorguk.ukuu.org.uk \
--to=alan@lxorguk.ukuu.org.uk \
--cc=castet.matthieu@free.fr \
--cc=linux-kernel@vger.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
all inboxes | Powered by JetHome®