[maint] batman-adv: Fix ICMP RR ethernet access after skb_linearize

Message ID 1464549952-27830-1-git-send-email-sven@narfation.org (mailing list archive)
State Accepted, archived
Commit f6c80c29ef4e8b45b715976107b7ae06fc0be3a0
Delegated to: Marek Lindner
Headers

Commit Message

Sven Eckelmann May 29, 2016, 7:25 p.m. UTC
  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: bb69cb678d37 ("batman-adv: generalize batman-adv icmp packet handling")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 net/batman-adv/routing.c | 1 +
 1 file changed, 1 insertion(+)
  

Comments

Marek Lindner June 6, 2016, 3:35 p.m. UTC | #1
On Sunday, May 29, 2016 21:25:52 Sven Eckelmann wrote:
> 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: bb69cb678d37 ("batman-adv: generalize batman-adv icmp packet
> handling") Signed-off-by: Sven Eckelmann <sven@narfation.org>
> ---
>  net/batman-adv/routing.c | 1 +
>  1 file changed, 1 insertion(+)

Applied in revision f6c80c2.

Thanks,
Marek
  

Patch

diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index 0c0c30e..27e07dd 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -374,6 +374,7 @@  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)