linux-kernel - Re: [BUG] 2.6.25-rc3 hangs in early boot on Sun Ultra5

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Message-ID: <alpine.LFD.1.00.0802270858450.7583@apollo.tec.linutronix.de>
Date:	Wed, 27 Feb 2008 09:02:22 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	David Miller <davem@...emloft.net>
cc:	mikpe@...uu.se, sparclinux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [BUG] 2.6.25-rc3 hangs in early boot on Sun Ultra5

On Tue, 26 Feb 2008, David Miller wrote:
> What the FUTEX checking code is doing now is doing a "user" access
> with set_fs(KERNEL_DS) since it runs from the kernel bootup early init
> sequence.  And this is illegal according to the existing checks.
> 
> When we do set_fs(KERNEL_DS) then pass a "user" pointer down
> into a system call or something like that, we give it a pointer
> that "cannot fault".  So if we get into the fault handling
> path here for a case like that we really do want to scream and
> print out an OOPS message in my opinion.

So it would be correct to set_fs(USER_DS) then do the check and switch
back to KERNEL_DS ?
 
> I realize that not many platforms other than sparc64 can check
> for things this precisely, but it's something to consider.

Hmm, I missed that.
 
> Did this FUTEX change go into -stable too?

It's queued, AFAIK

Thanks,
	tglx
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