linux-kernel - Re: [PATCH] lib: introduce strdup_from

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Message-ID: <20110603133726.0e55d27e@schlenkerla.am.freescale.net>
Date:	Fri, 3 Jun 2011 13:37:26 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Alexey Dobriyan <adobriyan@...il.com>
CC:	Timur Tabi <timur@...escale.com>, <alan@...rguk.ukuu.org.uk>,
	<linux-kernel@...r.kernel.org>, <akpm@...ux-foundation.org>
Subject: Re: [PATCH] lib: introduce strdup_from_user

On Fri, 3 Jun 2011 21:26:21 +0300
Alexey Dobriyan <adobriyan@...il.com> wrote:

> On Fri, Jun 3, 2011 at 9:22 PM, Timur Tabi <timur@...escale.com> wrote:
> > Alexey Dobriyan wrote:
> >> NAK
> >> It accesses userspace data twice.
> >
> > What's wrong with that?
> 
> If mm is shared, data can or will change under you.
>
> > How else is it supposed to know how much to allocate
> > without using strlen first?
> 
> I don't know.
> What I know is that your function doesn't guarantee NUL-termination.

If the only issue is NUL-termination (and I think that's the only issue,
everything else is userspace shooting itself in the foot), just stick
"str[len] = 0" at the end.

-Scott

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