linux-kernel - [PATCH 4.2.y-ckt 201/206] batman-adv: fix skb deref after free

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Date:	Thu,  9 Jun 2016 14:16:50 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Florian Westphal <fw@...len.de>,
	Marek Lindner <mareklindner@...mailbox.ch>,
	Antonio Quartulli <a@...table.cc>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 201/206] batman-adv: fix skb deref after free

4.2.8-ckt12 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Florian Westphal <fw@...len.de>

commit 63d443efe8be2c1d02b30d7e4edeb9aa085352b3 upstream.

batadv_send_skb_to_orig() calls dev_queue_xmit() so we can't use skb->len.

Fixes: 953324776d6d ("batman-adv: network coding - buffer unicast packets before forward")
Signed-off-by: Florian Westphal <fw@...len.de>
Reviewed-by: Sven Eckelmann <sven@...fation.org>
Signed-off-by: Marek Lindner <mareklindner@...mailbox.ch>
Signed-off-by: Antonio Quartulli <a@...table.cc>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 net/batman-adv/routing.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index cf57b20..fe25db2 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -585,6 +585,7 @@ static int batadv_route_unicast_packet(struct sk_buff *skb,
 	struct batadv_unicast_packet *unicast_packet;
 	struct ethhdr *ethhdr = eth_hdr(skb);
 	int res, hdr_len, ret = NET_RX_DROP;
+	unsigned int len;
 
 	unicast_packet = (struct batadv_unicast_packet *)skb->data;
 
@@ -625,6 +626,7 @@ static int batadv_route_unicast_packet(struct sk_buff *skb,
 	if (hdr_len > 0)
 		batadv_skb_set_priority(skb, hdr_len);
 
+	len = skb->len;
 	res = batadv_send_skb_to_orig(skb, orig_node, recv_if);
 
 	/* translate transmit result into receive result */
@@ -632,7 +634,7 @@ static int batadv_route_unicast_packet(struct sk_buff *skb,
 		/* skb was transmitted and consumed */
 		batadv_inc_counter(bat_priv, BATADV_CNT_FORWARD);
 		batadv_add_counter(bat_priv, BATADV_CNT_FORWARD_BYTES,
-				   skb->len + ETH_HLEN);
+				   len + ETH_HLEN);
 
 		ret = NET_RX_SUCCESS;
 	} else if (res == NET_XMIT_POLICED) {
-- 
2.7.4