[PATCH net-next 2/2] net: erspan: reload pointer after pskb_may_pull

[William Tu]

pskb_may_pull() can change skb->data, so we need to re-load pkt_md
and ershdr at the right place.

Fixes: 94d7d8f29287 ("ip6_gre: add erspan v2 support")
Fixes: f551c91de262 ("net: erspan: introduce erspan v2 for ip_gre")
Signed-off-by: William Tu <u9012...@gmail.com>
Cc: Haishuang Yan <yanhaishu...@cmss.chinamobile.com>
---
 net/ipv4/ip_gre.c  | 4 +++-
 net/ipv6/ip6_gre.c | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 1ca7451ff898..02a34098afb0 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -279,7 +279,6 @@ static int erspan_rcv(struct sk_buff *skb, struct 
tnl_ptk_info *tpi,
         * Use ERSPAN 10-bit session ID as key.
         */
        tpi->key = cpu_to_be32(ntohs(ershdr->session_id) & ID_MASK);
-       pkt_md = (struct erspan_metadata *)(ershdr + 1);
        tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex,
                                  tpi->flags | TUNNEL_KEY,
                                  iph->saddr, iph->daddr, tpi->key);
@@ -289,6 +288,9 @@ 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),
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index b3e4e0384f36..87b9892dfa23 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -515,7 +515,6 @@ static int ip6erspan_rcv(struct sk_buff *skb, int 
gre_hdr_len,
 
        ver = (ntohs(ershdr->ver_vlan) & VER_MASK) >> VER_OFFSET;
        tpi->key = cpu_to_be32(ntohs(ershdr->session_id) & ID_MASK);
-       pkt_md = (struct erspan_metadata *)(ershdr + 1);
 
        tunnel = ip6gre_tunnel_lookup(skb->dev,
                                      &ipv6h->saddr, &ipv6h->daddr, tpi->key,
@@ -526,6 +525,9 @@ 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)
-- 
2.7.4