linux-kernel - Re: strict copy_from

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Date:	Mon, 4 Jan 2010 17:43:08 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>, David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: strict copy_from_user checks issues?

On Mon, 4 Jan 2010 16:43:45 +0100
Heiko Carstens <heiko.carstens@...ibm.com> wrote:

> Hi Arjan,
> 
> I was just about to port the strict copy_from_user checks to s390, but
> I have some issues with it:
> 
> Is there a reason why there isn't a generic infrastructure that simply
> can be 'selected' by each architecure? I guess there isn't ;)

the compiler.h side is already generic; just that the copy from user
itself is different between architectures.

> x86 and sparc return -EFAULT in copy_from_user instead of the number
> of not copied bytes as it should in case of a detected buffer
> overflow. That might have unwanted side effects. I would guess that
> is a bug.

killing the bad guy in case of a real buffer overflow is appropriate..
this should never trigger for legitimate users.

> 
> Warnings cannot be switched off anymore as it was the case in your
> first version. However gcc seems to report quite a few false
> positives so it would be good if it could be turned off again.

hmm I thought most got fixed.. I'd be surprised if this part is
architecture specific.....
I rather fix the few cases left than disable the warning to be honest.
It's not many, at least not on x86.


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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