2019-07-25 18:10:54

by Haishuang Yan

Subject: [PATCH] ip6_tunnel: fix possible use-after-free on xmit

ip4ip6/ip6ip6 tunnels run iptunnel_handle_offloads on xmit which
can cause a possible use-after-free accessing iph/ipv6h pointer
since the packet will be 'uncloned' running pskb_expand_head if
it is a cloned gso skb.

Fixes: 0e9a709560db ("ip6_tunnel, ip6_gre: fix setting of DSCP on encapsulated packets")
Signed-off-by: Haishuang Yan <[email protected]>
---
net/ipv6/ip6_tunnel.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 3134fbb..754a484 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1278,12 +1278,11 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
}

fl6.flowi6_uid = sock_net_uid(dev_net(dev), NULL);
+ dsfield = INET_ECN_encapsulate(dsfield, ipv4_get_dsfield(iph));

if (iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6))
return -1;

- dsfield = INET_ECN_encapsulate(dsfield, ipv4_get_dsfield(iph));
-
skb_set_inner_ipproto(skb, IPPROTO_IPIP);

err = ip6_tnl_xmit(skb, dev, dsfield, &fl6, encap_limit, &mtu,
@@ -1367,12 +1366,11 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
}

fl6.flowi6_uid = sock_net_uid(dev_net(dev), NULL);
+ dsfield = INET_ECN_encapsulate(dsfield, ipv6_get_dsfield(ipv6h));

if (iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6))
return -1;

- dsfield = INET_ECN_encapsulate(dsfield, ipv6_get_dsfield(ipv6h));
-
skb_set_inner_ipproto(skb, IPPROTO_IPV6);

err = ip6_tnl_xmit(skb, dev, dsfield, &fl6, encap_limit, &mtu,
--
1.8.3.1

2019-07-26 21:19:22

by David Miller

Subject: Re: [PATCH] ip6_tunnel: fix possible use-after-free on xmit

From: Haishuang Yan <[email protected]>
Date: Fri, 26 Jul 2019 00:40:17 +0800

> ip4ip6/ip6ip6 tunnels run iptunnel_handle_offloads on xmit which
> can cause a possible use-after-free accessing iph/ipv6h pointer
> since the packet will be 'uncloned' running pskb_expand_head if
> it is a cloned gso skb.
>
> Fixes: 0e9a709560db ("ip6_tunnel, ip6_gre: fix setting of DSCP on encapsulated packets")
> Signed-off-by: Haishuang Yan <[email protected]>

Applied and queued up for -stable, thanks.