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[4.4,14/48] batman-adv: Fix ICMP RR ethernet access after skb_linearize

Message ID 20200317232734.6127-15-sven@narfation.org
State New
Headers show
Series batman-adv: Pending fixes | expand

Commit Message

Sven Eckelmann March 17, 2020, 11:27 p.m. UTC 
commit 3b55e4422087f9f7b241031d758a0c65584e4297 upstream.

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>
---
 net/batman-adv/routing.c | 1 +
 1 file changed, 1 insertion(+)
diff mbox series

Patch

diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index de24ab1cf67f..477899ba7616 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -359,6 +359,7 @@  int batadv_recv_icmp_packet(struct sk_buff *skb,
 		if (skb_cow(skb, ETH_HLEN) < 0)
 			goto out;
 
+		ethhdr = eth_hdr(skb);
 		icmph = (struct batadv_icmp_header *)skb->data;
 		icmp_packet_rr = (struct batadv_icmp_packet_rr *)icmph;
 		if (icmp_packet_rr->rr_cur >= BATADV_RR_LEN)