linux-kernel - Re: [PATCH net v3] tipc: check minimum bearer MTU

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Date:   Fri, 02 Dec 2016 14:03:34 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     mkubecek@...e.cz
Cc:     jon.maloy@...csson.com, ying.xue@...driver.com,
        tipc-discussion@...ts.sourceforge.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, ben@...adent.org.uk,
        zhangqian-c@....cn
Subject: Re: [PATCH net v3] tipc: check minimum bearer MTU

From: Michal Kubecek <mkubecek@...e.cz>
Date: Fri,  2 Dec 2016 09:33:41 +0100 (CET)

> Qian Zhang (张谦) reported a potential socket buffer overflow in
> tipc_msg_build() which is also known as CVE-2016-8632: due to
> insufficient checks, a buffer overflow can occur if MTU is too short for
> even tipc headers. As anyone can set device MTU in a user/net namespace,
> this issue can be abused by a regular user.
> 
> As agreed in the discussion on Ben Hutchings' original patch, we should
> check the MTU at the moment a bearer is attached rather than for each
> processed packet. We also need to repeat the check when bearer MTU is
> adjusted to new device MTU. UDP case also needs a check to avoid
> overflow when calculating bearer MTU.
> 
> Fixes: b97bf3fd8f6a ("[TIPC] Initial merge")
> Signed-off-by: Michal Kubecek <mkubecek@...e.cz>
> Reported-by: Qian Zhang (张谦) <zhangqian-c@....cn>

Applied and queued up for -stable, thanks.