netdev - [PATCH] bonding: init notify_work earlier to avoid uninitialized use

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Message-Id: <20210517161335.e40fea7f895a.I8b8487a9c0b8f54716cf44fdae02185381b1f64e@changeid>
Date:   Mon, 17 May 2021 16:13:35 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     netdev@...r.kernel.org
Cc:     Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        Johannes Berg <johannes.berg@...el.com>,
        syzbot+bfda097c12a00c8cae67@...kaller.appspotmail.com
Subject: [PATCH] bonding: init notify_work earlier to avoid uninitialized use

From: Johannes Berg <johannes.berg@...el.com>

If bond_kobj_init() or later kzalloc() in bond_alloc_slave() fail,
then we call kobject_put() on the slave->kobj. This in turn calls
the release function slave_kobj_release() which will always try to
cancel_delayed_work_sync(&slave->notify_work), which shouldn't be
done on an uninitialized work struct.

Always initialize the work struct earlier to avoid problems here.

Syzbot bisected this down to a completely pointless commit, some
fault injection may have been at work here that caused the alloc
failure in the first place, which may interact badly with bisect.

Reported-by: syzbot+bfda097c12a00c8cae67@...kaller.appspotmail.com
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 drivers/net/bonding/bond_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 20bbda1b36e1..c5a646d06102 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1526,6 +1526,7 @@ static struct slave *bond_alloc_slave(struct bonding *bond,
 
 	slave->bond = bond;
 	slave->dev = slave_dev;
+	INIT_DELAYED_WORK(&slave->notify_work, bond_netdev_notify_work);
 
 	if (bond_kobj_init(slave))
 		return NULL;
@@ -1538,7 +1539,6 @@ static struct slave *bond_alloc_slave(struct bonding *bond,
 			return NULL;
 		}
 	}
-	INIT_DELAYED_WORK(&slave->notify_work, bond_netdev_notify_work);
 
 	return slave;
 }
-- 
2.31.1