netdev - Re: [PATCH] tipc: call tipc_rcv() only if bearer is up in tipc_udp

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Message-Id: <20171128.095837.899409439582426451.davem@davemloft.net>
Date:   Tue, 28 Nov 2017 09:58:37 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     tommi.t.rantala@...ia.com
Cc:     jon.maloy@...csson.com, ying.xue@...driver.com,
        netdev@...r.kernel.org, tipc-discussion@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tipc: call tipc_rcv() only if bearer is up in
 tipc_udp_recv()

From: Tommi Rantala <tommi.t.rantala@...ia.com>
Date: Tue, 28 Nov 2017 14:53:15 +0200

> Call tipc_rcv() only if bearer is up in tipc_udp_recv().
> Fixes a rare TIPC div-by-zero crash in tipc_node_calculate_timer():
> 
> We're enabling a bearer, but it's not yet up and fully initialized.
> At the same time we receive a discovery packet, and in tipc_udp_recv()
> we end up calling tipc_rcv() with the not-yet-initialized bearer,
> causing later a div-by-zero crash in tipc_node_calculate_timer().

You're also now ignoring any error being returned by tipc_udp_rcast_disc().

> -
> -	if (unlikely(msg_user(hdr) == LINK_CONFIG)) {
> -		err = tipc_udp_rcast_disc(b, skb);
> -		if (err)
> -			goto rcu_out;
> +	} else {
> +		if (unlikely(b && msg_user(hdr) == LINK_CONFIG))
> +			tipc_udp_rcast_disc(b, skb);
> +		kfree_skb(skb);
>  	}

Either put the 'err' propagation back or clearly explain in your
commit log message why this part of the change if absolutely essential
for this bug fix.

Thank you.