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Commit 2a3cabae authored by Lorenzo Bianconi's avatar Lorenzo Bianconi Committed by David S. Miller
Browse files

net: ip6_gre: fix possible use-after-free in ip6erspan_rcv 



erspan_v6 tunnels run __iptunnel_pull_header on received skbs to remove
erspan header. This can determine a possible use-after-free accessing
pkt_md pointer in ip6erspan_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 492b67e2

net/ipv6/ip6_gre.c

+13 −7
Original line number Diff line number Diff line
@@ -525,10 +525,10 @@ static int ip6gre_rcv(struct sk_buff *skb, const struct tnl_ptk_info *tpi) 
}



static int ip6erspan_rcv(struct sk_buff *skb,

			 struct tnl_ptk_info *tpi)

			 struct tnl_ptk_info *tpi,

			 int gre_hdr_len)

{

	struct erspan_base_hdr *ershdr;

	struct erspan_metadata *pkt_md;

	const struct ipv6hdr *ipv6h;

	struct erspan_md2 *md2;

	struct ip6_tnl *tunnel;
@@ -547,18 +547,16 @@ static int ip6erspan_rcv(struct sk_buff *skb, 
		if (unlikely(!pskb_may_pull(skb, len)))

			return PACKET_REJECT;



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

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



		if (__iptunnel_pull_header(skb, len,

					   htons(ETH_P_TEB),

					   false, false) < 0)

			return PACKET_REJECT;



		if (tunnel->parms.collect_md) {

			struct erspan_metadata *pkt_md, *md;

			struct metadata_dst *tun_dst;

			struct ip_tunnel_info *info;

			struct erspan_metadata *md;

			unsigned char *gh;

			__be64 tun_id;

			__be16 flags;
@@ -571,6 +569,14 @@ static int ip6erspan_rcv(struct sk_buff *skb, 
			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			 * old pkt_md is no longer valid and we need to reset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));

			info = &tun_dst->u.tun_info;

			md = ip_tunnel_info_opts(info);

			md->version = ver;
@@ -607,7 +613,7 @@ static int gre_rcv(struct sk_buff *skb) 


	if (unlikely(tpi.proto == htons(ETH_P_ERSPAN) ||

		     tpi.proto == htons(ETH_P_ERSPAN2))) {

		if (ip6erspan_rcv(skb, &tpi) == PACKET_RCVD)

		if (ip6erspan_rcv(skb, &tpi, hdr_len) == PACKET_RCVD)

			return 0;

		goto out;

	}