linux-kernel - Re: [PATCH] sparc: copy_from_user() should not return -EFAULT

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Date:	Tue, 5 Jan 2010 19:20:40 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Heiko Carstens <heiko.carstens@...ibm.com>,
	Arnd Bergmann <arnd@...db.de>, Ingo Molnar <mingo@...e.hu>,
	David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sparc: copy_from_user() should not return -EFAULT

On Tue, 05 Jan 2010 18:27:18 +0100
Andi Kleen <andi@...stfloor.org> wrote:

> Heiko Carstens <heiko.carstens@...ibm.com> writes:
> 
> > Subject: [PATCH] sparc: copy_from_user() should not return -EFAULT
> >
> > From: Heiko Carstens <heiko.carstens@...ibm.com>
> >
> > Callers of copy_from_user() expect it to return the number of bytes
> > it could not copy. In no case it is supposed to return -EFAULT.
> >
> > In case of a detected buffer overflow just return the requested
> > length. In addition one could think of a memset that would clear
> > the size of the target object.
> 
> Ouch! I would expect this is likely exploitable, e.g. in mount

yeah once you have the buffer overflow there might be another exploit
instead.. so yes needs to be fixed.



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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