linux-kernel - Re: [PATCHv2 net] bonding: fix missed rcu protection

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Date:   Tue, 17 May 2022 13:32:58 -0400
From:   Jonathan Toppins <jtoppins@...hat.com>
To:     liuhangbin@...il.com
Cc:     andy@...yhouse.net, davem@...emloft.net, dsahern@...il.com,
        eric.dumazet@...il.com, j.vosburgh@...il.com, jtoppins@...hat.com,
        kuba@...nel.org, netdev@...r.kernel.org, pabeni@...hat.com,
        syzbot+92beb3d46aab498710fa@...kaller.appspotmail.com,
        vfalico@...il.com, vladimir.oltean@....com,
        Eric Dumazet <edumazet@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 net] bonding: fix missed rcu protection

Signed-off-by: Jonathan Toppins <jtoppins@...hat.com>
---
RESEND, list still didn't receive my last version

The diffstat is slightly larger but IMO a slightly more readable version.
When I was reading v2 I found myself jumping around.
I only compile tested it, so YMMV.

If this amount of change is too much v2 from Hangbin looks correct to
me.

 drivers/net/bonding/bond_main.c | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 38e152548126..f9d27b63c454 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -5591,23 +5591,32 @@ 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;
 
+	rcu_read_lock();
 	real_dev = bond_option_active_slave_get_rcu(bond);
-	if (real_dev) {
-		ops = real_dev->ethtool_ops;
-		phydev = real_dev->phydev;
-
-		if (phy_has_tsinfo(phydev)) {
-			return phy_ts_info(phydev, info);
-		} else if (ops->get_ts_info) {
-			return ops->get_ts_info(real_dev, info);
-		}
-	}
+	if (real_dev)
+		dev_hold(real_dev);
+	rcu_read_unlock();
+
+	if (!real_dev)
+		goto software;
 
+	ops = real_dev->ethtool_ops;
+	phydev = real_dev->phydev;
+
+	if (phy_has_tsinfo(phydev))
+		ret = phy_ts_info(phydev, info);
+	else if (ops->get_ts_info)
+		ret = ops->get_ts_info(real_dev, info);
+
+	dev_put(real_dev);
+	return ret;
+
+software:
 	info->so_timestamping = SOF_TIMESTAMPING_RX_SOFTWARE |
 				SOF_TIMESTAMPING_SOFTWARE;
 	info->phc_index = -1;
-
 	return 0;
 }
 
-- 
2.27.0