From: William Lee Irwin III <wli@holomorphy.com>
To: Jamie Lokier <jamie@shareable.org>
Cc: linux-kernel@vger.kernel.org, Michael Kerrisk <michael.kerrisk@gmx.net>
Subject: Re: Testing PROT_NONE and other protections, and a surprise
Date: Wed, 30 Jun 2004 20:35:18 -0700 [thread overview]
Message-ID: <20040701033518.GT21066@holomorphy.com> (raw)
In-Reply-To: <20040701032606.GA1564@mail.shareable.org>
William Lee Irwin III wrote:
>> It would be a bug if copy_to_user()/copy_from_user() failed to return
>> errors on attempted copies to/from areas with PROT_NONE protection.
>> I recommend writing a testcase and submitting it to LTP. I'll follow up
>> with an additional suggestion.
On Thu, Jul 01, 2004 at 04:26:06AM +0100, Jamie Lokier wrote:
> I've just written a thorough test. The attached program tries every
> combination of PROT_* flags, and tells you what protection you really get.
> I don't know how tests get into LTP; perhaps I can leave that to you?
> When running it on i386, I got a *huge* surprise (to me). A
> PROT_WRITE-only page can sometimes fault on read or exec. This is the
> output:
This is unsurprising. The permissions can't be represented in pagetables,
but can opportunistically be enforced when exceptions are taken for other
reasons (e.g. TLB invalidations related to page replacement).
-- wli
next prev parent reply other threads:[~2004-07-01 3:35 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 [this message]
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
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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