netdev - Re: [PATCH net] team: grab team lock during team_change_rx

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Message-ID: <aCYUezCpbcadrQfu@mini-arch>
Date: Thu, 15 May 2025 09:21:15 -0700
From: Stanislav Fomichev <stfomichev@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
	pabeni@...hat.com, jiri@...nulli.us, andrew+netdev@...n.ch,
	sdf@...ichev.me, linux-kernel@...r.kernel.org,
	syzbot+53485086a41dbb43270a@...kaller.appspotmail.com
Subject: Re: [PATCH net] team: grab team lock during team_change_rx_flags

On 05/15, Stanislav Fomichev wrote:
> On 05/15, Jakub Kicinski wrote:
> > On Wed, 14 May 2025 15:03:19 -0700 Stanislav Fomichev wrote:
> > > --- a/drivers/net/team/team_core.c
> > > +++ b/drivers/net/team/team_core.c
> > > @@ -1778,8 +1778,8 @@ static void team_change_rx_flags(struct net_device *dev, int change)
> > >  	struct team_port *port;
> > >  	int inc;
> > >  
> > > -	rcu_read_lock();
> > > -	list_for_each_entry_rcu(port, &team->port_list, list) {
> > > +	mutex_lock(&team->lock);
> > > +	list_for_each_entry(port, &team->port_list, list) {
> > 
> > I'm not sure if change_rx_flags is allowed to sleep.
> > Could you try to test it on a bond with a child without IFF_UNICAST_FLT,
> > add an extra unicast address to the bond and remove it?
> > That should flip promisc on and off IIUC.
> 
> I see, looks like you're concerned about addr_list_lock spin lock in
> dev_set_rx_mode? (or other callers of __dev_set_rx_mode) Let me try
> to reproduce with your example, but seems like it's an issue, yes
> and we have a lot of ndo_change_rx_flags callbacks that are sleepable :-(

Hmm, both bond and team set IFF_UNICAST_FLT, so it seems adding/removing uc
address on the bonding device should not flip promisc. But still will
verify for real.