Re: [PATCH] bonding: Fix broken promiscuity reference counting issue

[David Miller <davem@davemloft.net>]

From: Neil Horman <nhorman@tuxdriver.com>
Date: Fri, 27 Sep 2013 12:22:15 -0400

> Recently grabbed this report:
> https://bugzilla.redhat.com/show_bug.cgi?id=1005567
> 
> Of an issue in which the bonding driver, with an attached vlan encountered the
> following errors when bond0 was taken down and back up:
> 
> dummy1: promiscuity touches roof, set promiscuity failed. promiscuity feature of
> device might be broken.
> 
> The error occurs because, during __bond_release_one, if we release our last
> slave, we take on a random mac address and issue a NETDEV_CHANGEADDR
> notification.  With an attached vlan, the vlan may see that the vlan and bond
> mac address were in sync, but no longer are.  This triggers a call to dev_uc_add
> and dev_set_rx_mode, which enables IFF_PROMISC on the bond device.  Then, when
> we complete __bond_release_one, we use the current state of the bond flags to
> determine if we should decrement the promiscuity of the releasing slave.  But
> since the bond changed promiscuity state during the release operation, we
> incorrectly decrement the slave promisc count when it wasn't in promiscuous mode
> to begin with, causing the above error
> 
> Fix is pretty simple, just cache the bonding flags at the start of the function
> and use those when determining the need to set promiscuity.
> 
> This is also needed for the ALLMULTI flag
> 
> CC: Jay Vosburgh <fubar@us.ibm.com>
> CC: Andy Gospodarek <andy@greyhouse.net>
> CC: Mark Wu <wudxw@linux.vnet.ibm.com>
> CC: "David S. Miller" <davem@davemloft.net>
> Reported-by: Mark Wu <wudxw@linux.vnet.ibm.com>

Applied.