netdev - Re: [PATCH net-next-2.6] filter: add a security check at install time

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Message-ID: <AANLkTim8+9AA61HwcCQp3p7cSjzaTqerdd4Wtm-28kAt@mail.gmail.com>
Date:	Thu, 2 Dec 2010 16:11:08 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, hagen@...u.net,
	wirelesser@...il.com, netdev@...r.kernel.org,
	Dan Rosenberg <drosenberg@...curity.com>
Subject: Re: [PATCH net-next-2.6] filter: add a security check at install time

On Thu, Dec 2, 2010 at 2:46 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> [PATCH v2 net-next-2.6] filter: add a security check at install time
>
> We added some security checks in commit 57fe93b374a6
> (filter: make sure filters dont read uninitialized memory) to close a
> potential leak of kernel information to user.
>
> This added a potential extra cost at run time, while we can perform a
> check of the filter itself, to make sure a malicious user doesnt try to
> abuse us.
>
> This patch adds a check_loads() function, whole unique purpose is to
> make this check, allocating a temporary array of mask. We scan the
> filter and propagate a bitmask information, telling us if a load M(K) is
> allowed because a previous store M(K) is guaranteed. (So that
> sk_run_filter() can possibly not read unitialized memory)
>
> Note: this can uncover application bug, denying a filter attach,
> previously allowed.
>
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> Cc: Dan Rosenberg <drosenberg@...curity.com>
> Cc: Changli Gao <xiaosuo@...il.com>

It seems correct to me now.

Acked-by: Changli Gao <xiaosuo@...il.com>

-- 
Regards,
Changli Gao(xiaosuo@...il.com)
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