erspan: fix version 1 check in gre_parse_header()

Both version 0 and version 1 use ETH_P_ERSPAN, but version 0 does not
have an erspan header. So the check in gre_parse_header() is wrong,
we have to distinguish version 1 from version 0.

We can just check the gre header length like is_erspan_type1().

Fixes: cb73ee40b1b3 ("net: ip_gre: use erspan key field for tunnel lookup")
Reported-by: syzbot+f583ce3d4ddf9836b27a@syzkaller.appspotmail.com
Cc: William Tu <u9012063@gmail.com>
Cc: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
index 66fdbfe..5d1e6fe 100644 (file)
--- a/net/ipv4/gre_demux.c
+++ b/net/ipv4/gre_demux.c
@@ -128,7 +128,7 @@ int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
         * to 0 and sets the configured key in the
         * inner erspan header field
         */
-       if (greh->protocol == htons(ETH_P_ERSPAN) ||
+       if ((greh->protocol == htons(ETH_P_ERSPAN) && hdr_len != 4) ||
            greh->protocol == htons(ETH_P_ERSPAN2)) {
                struct erspan_base_hdr *ershdr;