From: Matt Mackall <mpm@selenic.com>
To: Kyle Moffett <mrmacman_g4@mac.com>
Cc: Jamie Lokier <jamie@shareable.org>,
lkml List <linux-kernel@vger.kernel.org>
Subject: Re: [OT] Testing PROT_NONE and other protections, and a surprise
Date: Thu, 1 Jul 2004 11:37:27 -0500 [thread overview]
Message-ID: <20040701163726.GH5414@waste.org> (raw)
In-Reply-To: <9628EAFE-CB6F-11D8-947A-000393ACC76E@mac.com>
On Thu, Jul 01, 2004 at 11:01:52AM -0400, Kyle Moffett wrote:
> On Jul 01, 2004, at 10:50, Jamie Lokier wrote:
> >Kyle Moffett wrote:
> >>>The error code is -1, aka. MAP_FAILED.
> >>Oops! I guess I was just lucky that part didn't fail :-D On the
> >>other hand, it couldn't legally return 0 anyway, could it?
> >
> >Yes it could -- if you request a mapping at address 0 with MAP_FIXED.
> >A few OSes won't do that, but Linux and many others will.
>
> That allows untrapped dereferencing of a NULL pointer. IMHO, that
> would be a very unintelligent thing for a program to do, to deny itself
> the bug-catching features provided therein, but it's interesting to see
> that it is possible.
A typical use is vm86-based emulation of 16-bit DOS where there's data
in the immediate vicinity of NULL.
--
Mathematics is the supreme nostalgia of our time.
next prev parent reply other threads:[~2004-07-01 16:37 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-06-30 2:44 A question about PROT_NONE on ARM and ARM26 Jamie Lokier
2004-06-30 3:38 ` William Lee Irwin III
2004-07-01 3:26 ` Testing PROT_NONE and other protections, and a surprise Jamie Lokier
2004-07-01 3:35 ` William Lee Irwin III
2004-07-01 4:01 ` Jamie Lokier
2004-07-01 3:44 ` Kyle Moffett
2004-07-01 4:11 ` Jamie Lokier
2004-07-01 4:59 ` Kyle Moffett
2004-07-01 12:39 ` Jamie Lokier
2004-07-01 14:43 ` [OT] " Kyle Moffett
2004-07-01 14:50 ` Jamie Lokier
2004-07-01 15:01 ` Kyle Moffett
2004-07-01 16:37 ` Matt Mackall [this message]
2004-07-01 17:26 ` Michael Driscoll
2004-07-02 7:37 ` Gabriel Paubert
2004-07-01 12:52 ` Russell King
2004-07-01 14:26 ` Richard Curnow
2004-06-30 8:16 ` A question about PROT_NONE on ARM and ARM26 Russell King
2004-06-30 14:59 ` Jamie Lokier
2004-06-30 15:22 ` Ian Molton
2004-06-30 18:26 ` Russell King
2004-06-30 19:14 ` Jamie Lokier
2004-06-30 19:23 ` Russell King
2004-06-30 20:15 ` Jamie Lokier
2004-06-30 22:59 ` Russell King
2004-06-30 23:30 ` Jamie Lokier
2004-06-30 23:48 ` Ian Molton
2004-07-01 1:59 ` Jamie Lokier
2004-07-01 1:05 ` Nicolas Pitre
2004-07-01 1:50 ` Jamie Lokier
2004-07-02 18:39 ` Russell King
2004-07-01 15:27 ` Scott Wood
2004-07-01 23:53 ` Jamie Lokier
2004-07-02 14:36 ` Scott Wood
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