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Date: Sun, 19 Oct 2003 20:17:57 +0200
From: Pavel Machek <pavel@ucw.cz>
To: Andrew Morton <akpm@osdl.org>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>, linux-ia64@vger.kernel.org,
       linux-kernel@vger.kernel.org
Subject: Re: [RFC] prevent "dd if=/dev/mem" crash
Message-ID: <20031019181756.GP1659@openzaurus.ucw.cz>
References: <200310171610.36569.bjorn.helgaas@hp.com> <20031017155028.2e98b307.akpm@osdl.org>
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Hi!

> > Old behavior:
> > 
> >     # dd if=/dev/mem of=/dev/null
> >     <unrecoverable machine check>
> 
> I recently fixed this for ia32 by changing copy_to_user() to not oops if
> the source address generated a fault.  Similarly copy_from_user() returns
> an error if the destination generates a fault.

Are you sure this is not hiding real errors? If you pass wrong
kernel ptr to copy_*_user, it should oops, not mask error with
-EFAULT.
Maybe another copy_user_unsafe should be created?
				Pavel
-- 
				Pavel
Written on sharp zaurus, because my Velo1 broke. If you have Velo you don't need...