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Date: Thu, 16 May 2002 23:56:11 +0000
From: Pavel Machek <pavel@suse.cz>
To: Larry McVoy <lm@work.bitmover.com>, Rusty Russell <rusty@rustcorp.com.au>,
        Larry McVoy <lm@bitmover.com>, linux-kernel@vger.kernel.org,
        alan@lxorguk.ukuu.org.uk
Subject: Re: AUDIT: copy_from_user is a deathtrap.
Message-ID: <20020516235610.D116@toy.ucw.cz>
In-Reply-To: <20020518200540.N8794@work.bitmover.com> <E179HtC-0001cB-00@wagner.rustcorp.com.au> <20020518210218.P8794@work.bitmover.com>
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Hi!

> > But as we all know, it is harder to remove a feature from Linux, than
> > to get the camel book through the eye of a needle (or something).
> 
> It's possible that I'm too tired to have grasped this, but if I have,
> you're all wet.  In all cases, read needs to return the number of bytes
> successfully moved.  If you ask for N and 1/2 of the way through N you
> are going to get a fault, and you return SEGFAULT, now how can I ever
> find out that N/2 bytes actually made it out to me?  I want to know that.
> If you are arguing that return N/2 is wrong, you are incorrect. 

You passed bad pointer to the kernel. You are broken. If you want to know
that N/2 was delivered, fix your code not to pass bad pointers.
								Pavel
-- 
Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt,
details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.