netdev - Re: [PATCH net v2] bonding: fix div by zero while enslaving and transmitting

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Message-Id: <20140913.171746.547311064738045536.davem@davemloft.net>
Date:	Sat, 13 Sep 2014 17:17:46 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	nikolay@...hat.com
Cc:	netdev@...r.kernel.org, eric.dumazet@...il.com, andy@...yhouse.net,
	j.vosburgh@...il.com, vfalico@...il.com
Subject: Re: [PATCH net v2] bonding: fix div by zero while enslaving and
 transmitting

From: Nikolay Aleksandrov <nikolay@...hat.com>
Date: Fri, 12 Sep 2014 17:38:18 +0200

> The problem is that the slave is first linked and slave_cnt is
> incremented afterwards leading to a div by zero in the modes that use it
> as a modulus. What happens is that in bond_start_xmit()
> bond_has_slaves() is used to evaluate further transmission and it becomes
> true after the slave is linked in, but when slave_cnt is used in the xmit
> path it is still 0, so fetch it once and transmit based on that. Since
> it is used only in round-robin and XOR modes, the fix is only for them.
> Thanks to Eric Dumazet for pointing out the fault in my first try to fix
> this.
  ...
> Fixes: 278b208375 ("bonding: initial RCU conversion")
> Signed-off-by: Nikolay Aleksandrov <nikolay@...hat.com>
> ---
> v2: Based on Eric's feedback change the fix to fetch the value once in a
>     local variable in the affected modes and to act based on that.

Applied and queued up for -stable, thanks.
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