linux-kernel - [PATCH 4.9 75/90] batman-adv: update data pointers after skb

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Message-Id: <20200319123951.602545138@linuxfoundation.org>
Date:   Thu, 19 Mar 2020 14:00:37 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Schiffer <mschiffer@...verse-factory.net>,
        Sven Eckelmann <sven@...fation.org>
Subject: [PATCH 4.9 75/90] batman-adv: update data pointers after skb_cow()

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: 78fc6bbe0aca ("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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/batman-adv/routing.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -930,7 +930,6 @@ 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 */
@@ -951,9 +950,13 @@ 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;
 			subtype = unicast_4addr_packet->subtype;
 			batadv_dat_inc_counter(bat_priv, subtype);