[ Upstream commit 2a3cabae4536edbcb21d344e7aa8be7a584d2afb ]
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: 1d7e2ed22f8d ("net: erspan: refactor existing erspan code") Signed-off-by: Lorenzo Bianconi lorenzo.bianconi@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv6/ip6_gre.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-)
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index 26f25b6e2833..438f1a5fd19a 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -524,11 +524,10 @@ static int ip6gre_rcv(struct sk_buff *skb, const struct tnl_ptk_info *tpi) return PACKET_REJECT; }
-static int ip6erspan_rcv(struct sk_buff *skb, int gre_hdr_len, - struct tnl_ptk_info *tpi) +static int ip6erspan_rcv(struct sk_buff *skb, 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 +546,16 @@ static int ip6erspan_rcv(struct sk_buff *skb, int gre_hdr_len, 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 +568,14 @@ static int ip6erspan_rcv(struct sk_buff *skb, int gre_hdr_len, 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+ /* skb can be uncloned in __iptunnel_pull_header, so + * old pkt_md is no longer valid and we need to reset + * it + */ + gh = skb_network_header(skb) + + skb_network_header_len(skb); + pkt_md = (struct erspan_metadata *)(gh + gre_hdr_len + +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 +612,7 @@ 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, hdr_len, &tpi) == PACKET_RCVD) + if (ip6erspan_rcv(skb, &tpi, hdr_len) == PACKET_RCVD) return 0; goto out; }