From: Martin Pool <mbp@samba.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: Andrew Morton <akpm@osdl.org>,
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
Date: Thu, 23 Oct 2003 18:33:16 +1000 [thread overview]
Message-ID: <20031023083316.GB5272@sourcefrog.net> (raw)
In-Reply-To: <20031019181756.GP1659@openzaurus.ucw.cz>
On 19 Oct 2003, Pavel Machek <pavel@ucw.cz> wrote:
> 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?
I think the problem is that reading memory that is mapped but doesn't
physically exist causes a Machine Check Assertion (like an NMI) rather
than a regular fault.
--
Martin
next prev parent reply other threads:[~2003-10-23 8:34 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-10-17 22:10 Bjorn Helgaas
2003-10-17 22:23 ` Matt Mackall
2003-10-17 22:50 ` Andrew Morton
2003-10-17 23:25 ` Bjorn Helgaas
2003-10-17 23:55 ` Andrew Morton
2003-10-18 0:15 ` William Lee Irwin III
2003-10-18 0:21 ` David Mosberger
2003-10-18 0:49 ` Andrew Morton
2003-10-18 1:31 ` Matt Chapman
2003-10-18 1:41 ` Andrew Morton
2003-10-18 1:48 ` David Mosberger
2003-10-18 2:01 ` Andrew Morton
2003-10-18 2:01 ` Matt Chapman
2003-10-19 11:25 ` Eric W. Biederman
2003-10-19 19:01 ` William Lee Irwin III
2003-10-20 15:17 ` Bjorn Helgaas
2003-10-20 18:48 ` David Mosberger
2003-10-20 15:58 ` fielding PCI bus timeouts - was: " Rich Altmaier
2003-10-20 17:42 ` [RFC] " Bjorn Helgaas
2003-10-23 21:05 ` Bjorn Helgaas
2003-10-19 18:17 ` Pavel Machek
2003-10-23 8:33 ` Martin Pool [this message]
2003-10-23 9:31 ` Zoltan Menyhart
2003-10-17 22:19 Luck, Tony
2003-10-17 22:40 ` Andreas Schwab
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