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Commit 492b67e2 authored by Lorenzo Bianconi's avatar Lorenzo Bianconi Committed by David S. Miller
Browse files

net: ip_gre: fix possible use-after-free in erspan_rcv 



erspan tunnels run __iptunnel_pull_header on received skbs to remove
gre and erspan headers. This can determine a possible use-after-free
accessing pkt_md pointer in erspan_rcv 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). Fix it resetting pkt_md pointer after
__iptunnel_pull_header

Fixes: 1d7e2ed2 ("net: erspan: refactor existing erspan code")
Signed-off-by: default avatarLorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b75bb8a5

net/ipv4/ip_gre.c

+10 −5
Original line number Diff line number Diff line
@@ -259,7 +259,6 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi, 
	struct net *net = dev_net(skb->dev);

	struct metadata_dst *tun_dst = NULL;

	struct erspan_base_hdr *ershdr;

	struct erspan_metadata *pkt_md;

	struct ip_tunnel_net *itn;

	struct ip_tunnel *tunnel;

	const struct iphdr *iph;
@@ -282,9 +281,6 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi, 
		if (unlikely(!pskb_may_pull(skb, len)))

			return PACKET_REJECT;



		ershdr = (struct erspan_base_hdr *)(skb->data + gre_hdr_len);

		pkt_md = (struct erspan_metadata *)(ershdr + 1);



		if (__iptunnel_pull_header(skb,

					   len,

					   htons(ETH_P_TEB),
@@ -292,8 +288,9 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi, 
			goto drop;



		if (tunnel->collect_md) {

			struct erspan_metadata *pkt_md, *md;

			struct ip_tunnel_info *info;

			struct erspan_metadata *md;

			unsigned char *gh;

			__be64 tun_id;

			__be16 flags;
@@ -306,6 +303,14 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi, 
			if (!tun_dst)

				return PACKET_REJECT;



			/* skb can be uncloned in __iptunnel_pull_header, so

			 * old pkt_md is no longer valid and we need to reset

			 * it

			 */

			gh = skb_network_header(skb) +

			     skb_network_header_len(skb);

			pkt_md = (struct erspan_metadata *)(gh + gre_hdr_len +

							    sizeof(*ershdr));

			md = ip_tunnel_info_opts(&tun_dst->u.tun_info);

			md->version = ver;

			md2 = &md->u.md2;