netdev - Re: [PATCH net-next] bonding: use WARN_ON instead of BUG in alb_upper_dev

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Date: Mon, 13 Nov 2023 16:31:39 -0800
From: Jay Vosburgh <jay.vosburgh@...onical.com>
To: Zhengchao Shao <shaozhengchao@...wei.com>
cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
    kuba@...nel.org, pabeni@...hat.com, andy@...yhouse.net,
    weiyongjun1@...wei.com, yuehaibing@...wei.com
Subject: Re: [PATCH net-next] bonding: use WARN_ON instead of BUG in alb_upper_dev_walk

Zhengchao Shao <shaozhengchao@...wei.com> wrote:

>If failed to allocate "tags" or could not find the final upper device from
>start_dev's upper list in bond_verify_device_path(), only the loopback
>detection of the current upper device should be affected, and the system is
>no need to be panic.
>
>Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>
>---
> drivers/net/bonding/bond_alb.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
>index dc2c7b979656..5519cc95b966 100644
>--- a/drivers/net/bonding/bond_alb.c
>+++ b/drivers/net/bonding/bond_alb.c
>@@ -984,8 +984,10 @@ static int alb_upper_dev_walk(struct net_device *upper,
> 	 */
> 	if (netif_is_macvlan(upper) && !strict_match) {
> 		tags = bond_verify_device_path(bond->dev, upper, 0);
>-		if (IS_ERR_OR_NULL(tags))
>-			BUG();
>+		if (IS_ERR_OR_NULL(tags)) {
>+			WARN_ON(1);
>+			return 0;

	This seems reasonable enough, although I'd suggest the using
WARN_ON_ONCE instead of WARN_ON.  Alternatively, this could stay as
WARN_ON if the above also returns non-zero in order to terminate the
netdev_walk_all_upper_dev_rcu walk.  The intent here is to avoid
spamming the log if there's a lot of macvlans above the bond.  If the
allocation in bond_verify_device_path failed, trying again immediately
seems likely to fail as well.

	We could also arrange for whatever called alb_upper_dev_walk to
reschedule at a slightly later time, but I don't think that's worth the
trouble.  The bond will by default resend learning packets once per
second, so issues related to a lost learning packet should resolve
relatively quickly.

	-J

>+		}
> 		alb_send_lp_vid(slave, upper->dev_addr,
> 				tags[0].vlan_proto, tags[0].vlan_id);
> 		kfree(tags);
>-- 
>2.34.1

---
	-Jay Vosburgh, jay.vosburgh@...onical.com