linux-kernel - [PATCH 3.16 369/410] batman-adv: update data pointers after skb

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Message-ID: <lsq.1528380321.303642619@decadent.org.uk>
Date:   Thu, 07 Jun 2018 15:05:21 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Matthias Schiffer" <mschiffer@...verse-factory.net>,
        "Sven Eckelmann" <sven@...fation.org>,
        "Simon Wunderlich" <sw@...onwunderlich.de>
Subject: [PATCH 3.16 369/410] batman-adv: update data pointers after skb_cow()

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Matthias Schiffer <mschiffer@...verse-factory.net>

commit bc44b78157f621ff2a2618fe287a827bcb094ac4 upstream.

batadv_check_unicast_ttvn() calls skb_cow(), so pointers into the SKB data
must be (re)set after calling it. The ethhdr variable is dropped
altogether.

Fixes: 7cdcf6dddc42 ("batman-adv: add UNICAST_4ADDR packet type")
Signed-off-by: Matthias Schiffer <mschiffer@...verse-factory.net>
Signed-off-by: Sven Eckelmann <sven@...fation.org>
Signed-off-by: Simon Wunderlich <sw@...onwunderlich.de>
[bwh: Backported to 3.16:
 - There's no ethhdr variable here
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -886,8 +886,6 @@ int batadv_recv_unicast_packet(struct sk
 	bool is4addr;
 
 	unicast_packet = (struct batadv_unicast_packet *)skb->data;
-	unicast_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data;
-
 	is4addr = unicast_packet->packet_type == BATADV_UNICAST_4ADDR;
 	/* the caller function should have already pulled 2 bytes */
 	if (is4addr)
@@ -907,9 +905,13 @@ int batadv_recv_unicast_packet(struct sk
 	if (!batadv_check_unicast_ttvn(bat_priv, skb, hdr_size))
 		return NET_RX_DROP;
 
+	unicast_packet = (struct batadv_unicast_packet *)skb->data;
+
 	/* packet for me */
 	if (batadv_is_my_mac(bat_priv, unicast_packet->dest)) {
 		if (is4addr) {
+			unicast_4addr_packet =
+				(struct batadv_unicast_4addr_packet *)skb->data;
 			batadv_dat_inc_counter(bat_priv,
 					       unicast_4addr_packet->subtype);
 			orig_addr = unicast_4addr_packet->src;