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net: fou: do not use guehdr after iptunnel_pull_offloads in gue_udp_recv

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gue tunnels run iptunnel_pull_offloads on received skbs. This can
determine a possible use-after-free accessing guehdr pointer since
the packet will be 'uncloned' running pskb_expand_head if it is a
cloned gso skb (e.g if the packet has been sent though a veth device)

Fixes: a09a4c8dd1 ("tunnels: Remove encapsulation offloads on decap")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Lorenzo Bianconi 2019-04-09 11:47:20 +02:00 committed by David S. Miller
parent d1841533e5
commit 988dc4a9a3
1 changed files with 3 additions and 1 deletions
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4
net/ipv4/fou.c
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@ -121,6 +121,7 @@ static int gue_udp_recv(struct sock *sk, struct sk_buff *skb)
struct guehdr *guehdr;
void *data;
u16 doffset = 0;
u8 proto_ctype;
if (!fou)
return 1;
@ -212,13 +213,14 @@ static int gue_udp_recv(struct sock *sk, struct sk_buff *skb)
if (unlikely(guehdr->control))
return gue_control_message(skb, guehdr);
proto_ctype = guehdr->proto_ctype;
__skb_pull(skb, sizeof(struct udphdr) + hdrlen);
skb_reset_transport_header(skb);
if (iptunnel_pull_offloads(skb))
goto drop;
return -guehdr->proto_ctype;
return -proto_ctype;
drop:
kfree_skb(skb);