netdev - Re: [PATCH RESEND net] bonding: fix missed rcu protection

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Message-ID: <YoMZvrPcgIm8k2b6@Laptop-X1>
Date:   Tue, 17 May 2022 11:42:54 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S . Miller" <davem@...emloft.net>,
        David Ahern <dsahern@...il.com>,
        Jonathan Toppins <jtoppins@...hat.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Paolo Abeni <pabeni@...hat.com>,
        syzbot+92beb3d46aab498710fa@...kaller.appspotmail.com,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH RESEND net] bonding: fix missed rcu protection

On Mon, May 16, 2022 at 06:10:28PM -0700, Jakub Kicinski wrote:
> Can't ->get_ts_info sleep now? It'd be a little sad to force it 
> to be atomic just because of one upper dev trying to be fancy.
> Maybe all we need to do is to take a ref on the real_dev?

Do you mean

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 38e152548126..b60450211579 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -5591,16 +5591,20 @@ static int bond_ethtool_get_ts_info(struct net_device *bond_dev,
 	const struct ethtool_ops *ops;
 	struct net_device *real_dev;
 	struct phy_device *phydev;
+	int ret = 0;
 
 	real_dev = bond_option_active_slave_get_rcu(bond);
 	if (real_dev) {
+		dev_hold(real_dev)
 		ops = real_dev->ethtool_ops;
 		phydev = real_dev->phydev;
 
 		if (phy_has_tsinfo(phydev)) {
-			return phy_ts_info(phydev, info);
+			ret = phy_ts_info(phydev, info);
+			goto out;
 		} else if (ops->get_ts_info) {
-			return ops->get_ts_info(real_dev, info);
+			ret = ops->get_ts_info(real_dev, info);
+			goto out;
 		}
 	}
 
@@ -5608,7 +5612,10 @@ static int bond_ethtool_get_ts_info(struct net_device *bond_dev,
 				SOF_TIMESTAMPING_SOFTWARE;
 	info->phc_index = -1;
 
-	return 0;
+out:
+	if (real_dev)
+		dev_put(real_dev);
+	return ret;
 }


This look OK to me.

Vladimir, Jay, WDYT?

> 
> Also please add a Link: to the previous discussion, it'd have been
> useful to get the context in which Vladimir suggested this.

OK, I will.

Thanks
Hangbin