[14/20] batman-adv: Place kref_get for softif_vlan near use

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From: Simon Wunderlich <sw@simonwunderlich.de>
To: davem@davemloft.net
Date: Mon, 22 Aug 2016 15:56:14 +0200
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Cc: netdev@vger.kernel.org, b.a.t.m.a.n@lists.open-mesh.org,
	Marek Lindner <mareklindner@neomailbox.ch>
Subject: [B.A.T.M.A.N.] [PATCH 14/20] batman-adv: Place kref_get for
	softif_vlan near use
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Commit Message

Simon Wunderlich Aug. 22, 2016, 1:56 p.m. UTC

  From: Sven Eckelmann <sven@narfation.org>

It is hard to understand why the refcnt is increased when it isn't done
near the actual place the new reference is used. So using kref_get right
before the place which requires the reference and in the same function
helps to avoid accidental problems caused by incorrect reference counting.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/soft-interface.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Sergei Shtylyov Aug. 23, 2016, 1:20 p.m. UTC | #1

Hello.

On 8/22/2016 4:56 PM, Simon Wunderlich wrote:

> From: Sven Eckelmann <sven@narfation.org>
>
> It is hard to understand why the refcnt is increased when it isn't done
> near the actual place the new reference is used. So using kref_get right
> before the place which requires the reference and in the same function
> helps to avoid accidental problems caused by incorrect reference counting.

     I don't think your boilerplate log works for this patch where you are 
*adding* the ref-counting.

> Signed-off-by: Sven Eckelmann <sven@narfation.org>
> Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
> Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
> ---
>  net/batman-adv/soft-interface.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
> index e508bf5..49e16b6 100644
> --- a/net/batman-adv/soft-interface.c
> +++ b/net/batman-adv/soft-interface.c
> @@ -594,6 +594,7 @@ int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
>  	}
>
>  	spin_lock_bh(&bat_priv->softif_vlan_list_lock);
> +	kref_get(&vlan->refcount);
>  	hlist_add_head_rcu(&vlan->list, &bat_priv->softif_vlan_list);
>  	spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
>
> @@ -604,6 +605,9 @@ int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
>  			    bat_priv->soft_iface->dev_addr, vid,
>  			    BATADV_NULL_IFINDEX, BATADV_NO_MARK);
>
> +	/* don't return reference to new softif_vlan */
> +	batadv_softif_vlan_put(vlan);
> +
>  	return 0;
>  }
>

MBR, Sergei

diff mbox

Patch

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index e508bf5..49e16b6 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -594,6 +594,7 @@  int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
 	}
 
 	spin_lock_bh(&bat_priv->softif_vlan_list_lock);
+	kref_get(&vlan->refcount);
 	hlist_add_head_rcu(&vlan->list, &bat_priv->softif_vlan_list);
 	spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
 
@@ -604,6 +605,9 @@  int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
 			    bat_priv->soft_iface->dev_addr, vid,
 			    BATADV_NULL_IFINDEX, BATADV_NO_MARK);
 
+	/* don't return reference to new softif_vlan */
+	batadv_softif_vlan_put(vlan);
+
 	return 0;
 }