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

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

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.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@syzkaller.appspotmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.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

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

[Jay Vosburgh]

Johannes Berg <johannes@sipsolutions.net> wrote:

>From: Johannes Berg <johannes.berg@intel.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@syzkaller.appspotmail.com
>Signed-off-by: Johannes Berg <johannes.berg@intel.com>

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

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

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Mon, 17 May 2021 16:13:35 +0200 you wrote:
> From: Johannes Berg <johannes.berg@intel.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.
> 
> [...]

Here is the summary with links:
  - bonding: init notify_work earlier to avoid uninitialized use
    https://git.kernel.org/netdev/net/c/35d96e631860

You are awesome, thank you!
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