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batman-adv: Fix ICMP RR ethernet access after skb_linearize

The skb_linearize may reallocate the skb. This makes the calculated pointer
for ethhdr invalid. But it the pointer is used later to fill in the RR
field of the batadv_icmp_packet_rr packet.

Instead re-evaluate eth_hdr after the skb_linearize+skb_cow to fix the
pointer and avoid the invalid read.

Fixes: da6b8c20a5b8 ("batman-adv: generalize batman-adv icmp packet handling")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Sven Eckelmann 9 years ago
parent
baceced932
commit
3b55e44220
1 changed files with 1 additions and 0 deletions
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  1. 1 0
      net/batman-adv/routing.c

+ 1 - 0
net/batman-adv/routing.c
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@@ -374,6 +374,7 @@ int batadv_recv_icmp_packet(struct sk_buff *skb,
 
 		if (skb_cow(skb, ETH_HLEN) < 0)
 
 		if (skb_cow(skb, ETH_HLEN) < 0)
 
 			goto out;
 
 			goto out;
 
 
 
+		ethhdr = eth_hdr(skb);
 
 		icmph = (struct batadv_icmp_header *)skb->data;
 
 		icmph = (struct batadv_icmp_header *)skb->data;
 
 		icmp_packet_rr = (struct batadv_icmp_packet_rr *)icmph;
 
 		icmp_packet_rr = (struct batadv_icmp_packet_rr *)icmph;
 
 		if (icmp_packet_rr->rr_cur >= BATADV_RR_LEN)
 
 		if (icmp_packet_rr->rr_cur >= BATADV_RR_LEN)