Repository : ssh://git@open-mesh.org/batman-adv On branch : master commit fee73a8578d308fb70186b99e936e4be0d5870f8 Author: Sven Eckelmann <sven(a)narfation.org> Date: Sat Mar 5 16:09:17 2016 +0100 batman-adv: Check hard_iface refcnt when receiving skb 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(a)narfation.org> Signed-off-by: Marek Lindner <mareklindner(a)neomailbox.ch> fee73a8578d308fb70186b99e936e4be0d5870f8 net/batman-adv/main.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/net/batman-adv/main.c b/net/batman-adv/main.c index 78c05a9..c8d8bc7 100644 --- a/net/batman-adv/main.c +++ b/net/batman-adv/main.c @@ -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; }