From mboxrd@z Thu Jan  1 00:00:00 1970
From: "David S. Miller" <davem@redhat.com>
Subject: Re: [PATCH] tun
Date: Mon, 15 Mar 2004 12:47:51 -0800
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To: Stephen Hemminger <shemminger@osdl.org>
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On Mon, 15 Mar 2004 10:28:10 -0800
Stephen Hemminger <shemminger@osdl.org> wrote:

> Tun verifies the user address before doing memcpy_from/toiovec.  There are
> two problems with this strategy.  First, it is possible on an SMP machine
> to construct cases where a page is unmmapped between the verify and the copy,
> and it is also faster to do the verification only once.

Yes, those verify_area calls are superfluous and racy.

Applied, thanks Stephen.