netdev - Re: [PATCH v2 net] ipv6: addrconf: validate new MTU before applying it

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Message-Id: <20150223.181645.1582799387342364278.davem@davemloft.net>
Date:	Mon, 23 Feb 2015 18:16:45 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	mleitner@...hat.com
Cc:	netdev@...r.kernel.org, sd@...asysnail.net
Subject: Re: [PATCH v2 net] ipv6: addrconf: validate new MTU before
 applying it

From: Marcelo Ricardo Leitner <mleitner@...hat.com>
Date: Mon, 23 Feb 2015 11:17:13 -0300

> Currently we don't check if the new MTU is valid or not and this allows
> one to configure a smaller than minimum allowed by RFCs or even bigger
> than interface own MTU, which is a problem as it may lead to packet
> drops.
> 
> If you have a daemon like NetworkManager running, this may be exploited
> by remote attackers by forging RA packets with an invalid MTU, possibly
> leading to a DoS. (NetworkManager currently only validates for values
> too small, but not for too big ones.)
> 
> The fix is just to make sure the new value is valid. That is, between
> IPV6_MIN_MTU and interface's MTU.
> 
> Note that similar check is already performed at
> ndisc_router_discovery(), for when kernel itself parses the RA.
> 
> Signed-off-by: Marcelo Ricardo Leitner <mleitner@...hat.com>

Applied, thanks.
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