From: David Mosberger <davidm@napali.hpl.hp.com>
To: Roland McGrath <roland@redhat.com>
Cc: davidm@hpl.hp.com, torvalds@transmeta.com, linux-kernel@vger.kernel.org
Subject: Re: FIXMAP-related change to mm/memory.c
Date: Thu, 12 Jun 2003 19:16:37 -0700 [thread overview]
Message-ID: <16105.13317.608868.581471@napali.hpl.hp.com> (raw)
In-Reply-To: <200306130207.h5D27eH22519@magilla.sf.frob.com>
>>>>> On Thu, 12 Jun 2003 19:07:40 -0700, Roland McGrath <roland@redhat.com> said:
Roland> The pte_user predicate was added just for this purpose. It
Roland> seems reasonable to me to replace its use with a new pair of
Roland> predicates, pte_user_read and pte_user_write, whose meaning
Roland> is clearly specified for precisely this purpose. That is,
Roland> those predicates check whether a user process should be
Roland> allowed to read/write the page via something like ptrace.
Roland> That's the obvious idea to me. But I have no special
Roland> opinions about this stuff myself. The current code is as it
Roland> is because that's what Linus wanted.
I considered a pte_user_read()/pte_user_write()-like approach, but
rejected it. First of all, it doesn't really help with execute-only
pages. Of course, we could add a pte_user_exec() and treat those
pages as readable, but that's not a good solution: just because we
want to make the gate page readable via ptrace() doesn't mean that we
want _all_ execute-only pages to be readable (it wouldn't make a
difference today, but I'm worried about someone adding other
execute-only pages further down the road, not being aware that
ptrace() would cause a potential security problem).
For ia64, I think we really want to say: if it's accessing the gate
page, allow reads. There is just no way we can infer that from
looking at the PTE itself.
Is there really a point in allowing other FIXMAP pages to be read via
ptrace() on x86?
--david
next prev parent reply other threads:[~2003-06-13 2:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-06-13 1:24 FIXMAP-related change to mm/memory.c David Mosberger
2003-06-13 2:07 ` Roland McGrath
2003-06-13 2:16 ` David Mosberger [this message]
2003-06-13 6:34 ` Roland McGrath
2003-06-13 6:37 ` David Mosberger
2003-06-13 6:56 ` Roland McGrath
2003-06-13 7:15 ` Andrew Morton
2003-06-15 6:51 ` Anton Blanchard
2003-06-13 7:17 ` David Mosberger
2003-06-13 5:24 ` Linus Torvalds
2003-06-13 7:28 ` [BUG] " Riley Williams
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