netdev - Re: [PATCH net] bonding: fix event handling for stacked bonds

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Date:   Fri, 12 Apr 2019 15:57:55 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Sabrina Dubroca <sd@...asysnail.net>
Cc:     netdev@...r.kernel.org, Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        Jarod Wilson <jarod@...hat.com>
Subject: Re: [PATCH net] bonding: fix event handling for stacked bonds

Fri, Apr 12, 2019 at 03:04:10PM CEST, sd@...asysnail.net wrote:
>When a bond is enslaved to another bond, bond_netdev_event() only
>handles the event as if the bond is a master, and skips treating the
>bond as a slave.
>
>This leads to a refcount leak on the slave, since we don't remove the
>adjacency to its master and the master holds a reference on the slave.
>
>Reproducer:
>  ip link add bondL type bond
>  ip link add bondU type bond
>  ip link set bondL master bondU
>  ip link del bondL

Out of curiosity, what is a usecase of stacked bonds? I don't see any.


>
>No "Fixes:" tag, this code is older than git history.
>
>Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
>---
>I also spotted some lockdep warnings when I started stacking random
>devices on top of random devices, I'm trying to clean that up too, but
>this fix is independent of that.
>
> drivers/net/bonding/bond_main.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index b59708c35faf..ee610721098e 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -3213,8 +3213,12 @@ static int bond_netdev_event(struct notifier_block *this,
> 		return NOTIFY_DONE;
> 
> 	if (event_dev->flags & IFF_MASTER) {
>+		int ret;
>+
> 		netdev_dbg(event_dev, "IFF_MASTER\n");
>-		return bond_master_netdev_event(event, event_dev);
>+		ret = bond_master_netdev_event(event, event_dev);
>+		if (ret != NOTIFY_DONE)
>+			return ret;
> 	}
> 
> 	if (event_dev->flags & IFF_SLAVE) {
>-- 
>2.21.0
>