linux-kernel - Re: noexec=on doesn't work

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Date:	Mon, 11 Dec 2006 17:01:12 -0500
From:	John Richard Moser <nigelenki@...cast.net>
To:	Eric Piel <Eric.Piel@...mplin-utc.net>
CC:	Kyle McMartin <kyle@...ntu.com>, linux-kernel@...r.kernel.org
Subject: Re: noexec=on doesn't work

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Eric Piel wrote:
> 12/09/2006 09:03 PM, Kyle McMartin wrote/a écrit:
>> On Sat, Dec 09, 2006 at 02:34:47PM -0500, John Richard Moser wrote:
>>> I have filed this as a distro bug with Ubuntu; it may be their issue, I
>>> haven't dug deep enough to find out.  I am posting this here to disperse
>>> the information breadth-first instead of depth-first, which will shorten
>>> the bug's life cycle if it turns out to be an upstream bug.
>>>
>>
>> NX requires the 64-bit page table entries (ie, PAE) which requires
>> CONFIG_HIGHMEM64G.
> 
> Somehow there is a problem: a user can explicitly put "noexec=on" and it
> will be silently ignored if the kernel doesn't have PAE support. I guess
> that currently no message is written because "noexec=on" is the
> _default_. Still, it would be fair to the user who added "noexec=on" on
> its command line that if it is not respected, either because the
> hardware doesn't support it or because the kernel doesn't support it, we
> display a warning saying it's hopeless.
> 

Would have saved me and others a lot of trouble if this happened, yes; I
wouldn't have written a test case and wtf'd at it for 5 days.  :)

> I'll send a patch if it seems meaningful to you,

Telling may be better than letting the user think; then again any
knowledgeable user should know based on his config (yes I know, by this
logic I should have known about the HIGHMEM64G thing).

> c u
> Eric
> 
> 
> 
> 

- --
    We will enslave their women, eat their children and rape their
    cattle!
                  -- Bosc, Evil alien overlord from the fifth dimension
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