netdev - Re: [PATCH] bonding: fix error handling if slave is busy (v2)

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Message-ID: <20111231161322.40b16d69@nehalam.linuxnetplumber.net>
Date:	Sat, 31 Dec 2011 16:13:22 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] bonding: fix error handling if slave is busy (v2)

On Sun, 01 Jan 2012 01:09:50 +0100
Nicolas de Pesloüan <nicolas.2p.debian@...il.com> wrote:

> Le 01/01/2012 00:26, Stephen Hemminger a écrit :
> > If slave device already has a receive handler registered, then the
> > error unwind of bonding device enslave function is broken.
> >
> > The following will leave a pointer to freed memory in the slave
> > device list, causing a later kernel panic.
> > # modprobe dummy
> > # ip li add dummy0-1 link dummy0 type macvlan
> > # modprobe bonding
> > # echo +dummy0>/sys/class/net/bond0/bonding/slaves
> >
> > The fix is to detach the slave (which removes it from the list)
> > in the unwind path.
> >
> > Signed-off-by: Stephen Hemminger<shemminger@...tta.com>
> 
> Thanks Stephen.
> 
> Reviewed-by: Nicolas de Pesloüan <nicolas.2p.debian@...e.fr>

The locking in bond driver is a tangled web.

Would be cleaner to get rid of bond->lock altogether.
Slave add/delete should be protected by RTNL, and the lookup should
be converted to RCU.  The problem is that bonding driver implements
own form of circular list to handle round-robin etc.


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