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batman-adv: Check hard_iface refcnt when receiving skb

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The receive function may start processing an incoming packet while the
hard_iface is shut down in a different context. All called functions called
with the batadv_hard_iface object belonging to the incoming interface would
have to check whether the reference counter is still > 0.

This is rather error-prone because this check can be forgotten easily.
Instead check the reference counter when receiving the object to make sure
that all called functions have a valid reference.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>
This commit is contained in:
Sven Eckelmann 2016-03-05 16:09:17 +01:00 committed by Antonio Quartulli
parent 273534468f
commit 4fe56e60ac
1 changed files with 13 additions and 1 deletions
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14
net/batman-adv/main.c
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@ -401,11 +401,19 @@ int batadv_batman_skb_recv(struct sk_buff *skb, struct net_device *dev,
hard_iface = container_of(ptype, struct batadv_hard_iface,
batman_adv_ptype);
/* Prevent processing a packet received on an interface which is getting
* shut down otherwise the packet may trigger de-reference errors
* further down in the receive path.
*/
if (!kref_get_unless_zero(&hard_iface->refcount))
goto err_out;
skb = skb_share_check(skb, GFP_ATOMIC);
/* skb was released by skb_share_check() */
if (!skb)
goto err_out;
goto err_put;
/* packet should hold at least type and version */
if (unlikely(!pskb_may_pull(skb, 2)))
@ -448,6 +456,8 @@ int batadv_batman_skb_recv(struct sk_buff *skb, struct net_device *dev,
if (ret == NET_RX_DROP)
kfree_skb(skb);
batadv_hardif_put(hard_iface);
/* return NET_RX_SUCCESS in any case as we
* most probably dropped the packet for
* routing-logical reasons.
@ -456,6 +466,8 @@ int batadv_batman_skb_recv(struct sk_buff *skb, struct net_device *dev,
err_free:
kfree_skb(skb);
err_put:
batadv_hardif_put(hard_iface);
err_out:
return NET_RX_DROP;
}