linux-kernel - [PATCH 4.14 72/99] batman-adv: update data pointers after skb

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Date:   Thu, 19 Mar 2020 14:03:50 +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>,
        Simon Wunderlich <sw@...onwunderlich.de>
Subject: [PATCH 4.14 72/99] 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: 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/batman-adv/routing.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -950,14 +950,10 @@ int batadv_recv_unicast_packet(struct sk
 	struct batadv_orig_node *orig_node = NULL, *orig_node_gw = NULL;
 	int check, hdr_size = sizeof(*unicast_packet);
 	enum batadv_subtype subtype;
-	struct ethhdr *ethhdr;
 	int ret = NET_RX_DROP;
 	bool is4addr, is_gw;
 
 	unicast_packet = (struct batadv_unicast_packet *)skb->data;
-	unicast_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data;
-	ethhdr = eth_hdr(skb);
-
 	is4addr = unicast_packet->packet_type == BATADV_UNICAST_4ADDR;
 	/* the caller function should have already pulled 2 bytes */
 	if (is4addr)
@@ -977,12 +973,14 @@ int batadv_recv_unicast_packet(struct sk
 	if (!batadv_check_unicast_ttvn(bat_priv, skb, hdr_size))
 		goto free_skb;
 
+	unicast_packet = (struct batadv_unicast_packet *)skb->data;
+
 	/* packet for me */
 	if (batadv_is_my_mac(bat_priv, unicast_packet->dest)) {
 		/* If this is a unicast packet from another backgone gw,
 		 * drop it.
 		 */
-		orig_addr_gw = ethhdr->h_source;
+		orig_addr_gw = eth_hdr(skb)->h_source;
 		orig_node_gw = batadv_orig_hash_find(bat_priv, orig_addr_gw);
 		if (orig_node_gw) {
 			is_gw = batadv_bla_is_backbone_gw(skb, orig_node_gw,
@@ -997,6 +995,8 @@ int batadv_recv_unicast_packet(struct sk
 		}
 
 		if (is4addr) {
+			unicast_4addr_packet =
+				(struct batadv_unicast_4addr_packet *)skb->data;
 			subtype = unicast_4addr_packet->subtype;
 			batadv_dat_inc_counter(bat_priv, subtype);