netdev - Re: [PATCH net] bridge: fix lockdep addr_list

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Date:	Fri, 15 Jan 2016 15:41:45 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	razor@...ckwall.org
Cc:	netdev@...r.kernel.org, nikolay@...ulusnetworks.com,
	vyasevic@...hat.com, stephen@...workplumber.org,
	bridge@...ts.linux-foundation.org, gospo@...ulusnetworks.com,
	roopa@...ulusnetworks.com
Subject: Re: [PATCH net] bridge: fix lockdep addr_list_lock false positive
 splat

From: Nikolay Aleksandrov <razor@...ckwall.org>
Date: Fri, 15 Jan 2016 19:03:54 +0100

> From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
> 
> After promisc mode management was introduced a bridge device could do
> dev_set_promiscuity from its ndo_change_rx_flags() callback which in
> turn can be called after the bridge's addr_list_lock has been taken
> (e.g. by dev_uc_add). This causes a false positive lockdep splat because
> the port interfaces' addr_list_lock is taken when br_manage_promisc()
> runs after the bridge's addr list lock was already taken.
> To remove the false positive introduce a custom bridge addr_list_lock
> class and set it on bridge init.
> A simple way to reproduce this is with the following:
> $ brctl addbr br0
> $ ip l add l br0 br0.100 type vlan id 100
> $ ip l set br0 up
> $ ip l set br0.100 up
> $ echo 1 > /sys/class/net/br0/bridge/vlan_filtering
> $ brctl addif br0 eth0
> Splat:
 ...
> CC: Vlad Yasevich <vyasevic@...hat.com>
> CC: Stephen Hemminger <stephen@...workplumber.org>
> CC: Bridge list <bridge@...ts.linux-foundation.org>
> CC: Andy Gospodarek <gospo@...ulusnetworks.com>
> CC: Roopa Prabhu <roopa@...ulusnetworks.com>
> Fixes: 2796d0c648c9 ("bridge: Automatically manage port promiscuous mode.")
> Reported-by: Andy Gospodarek <gospo@...ulusnetworks.com>
> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>

Applied and queued up for -stable, thanks Nikolay.