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

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Date:   Mon, 17 May 2021 08:39:59 -0700
From:   Jay Vosburgh <jay.vosburgh@...onical.com>
To:     Johannes Berg <johannes@...solutions.net>
cc:     netdev@...r.kernel.org, Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        Johannes Berg <johannes.berg@...el.com>,
        syzbot+bfda097c12a00c8cae67@...kaller.appspotmail.com
Subject: Re: [PATCH] bonding: init notify_work earlier to avoid uninitialized use

Johannes Berg <johannes@...solutions.net> wrote:

>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>

Acked-by: Jay Vosburgh <jay.vosburgh@...onical.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
>