[PATCH 5.3 082/140] erspan: fix the tun_info options_len check for erspan

[Greg Kroah-Hartman]

From: Xin Long <lucien.xin@xxxxxxxxx>

[ Upstream commit 2eb8d6d2910cfe3dc67dc056f26f3dd9c63d47cd ]

The check for !md doens't really work for ip_tunnel_info_opts(info) which
only does info + 1. Also to avoid out-of-bounds access on info, it should
ensure options_len is not less than erspan_metadata in both erspan_xmit()
and ip6erspan_tunnel_xmit().

Fixes: 1a66a836da ("gre: add collect_md mode to ERSPAN tunnel")
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv4/ip_gre.c  |    4 ++--
 net/ipv6/ip6_gre.c |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -509,9 +509,9 @@ static void erspan_fb_xmit(struct sk_buf
 	key = &tun_info->key;
 	if (!(tun_info->key.tun_flags & TUNNEL_ERSPAN_OPT))
 		goto err_free_skb;
-	md = ip_tunnel_info_opts(tun_info);
-	if (!md)
+	if (tun_info->options_len < sizeof(*md))
 		goto err_free_skb;
+	md = ip_tunnel_info_opts(tun_info);
 
 	/* ERSPAN has fixed 8 byte GRE header */
 	version = md->version;
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -980,9 +980,9 @@ static netdev_tx_t ip6erspan_tunnel_xmit
 		dsfield = key->tos;
 		if (!(tun_info->key.tun_flags & TUNNEL_ERSPAN_OPT))
 			goto tx_err;
-		md = ip_tunnel_info_opts(tun_info);
-		if (!md)
+		if (tun_info->options_len < sizeof(*md))
 			goto tx_err;
+		md = ip_tunnel_info_opts(tun_info);
 
 		tun_id = tunnel_id_to_key32(key->tun_id);
 		if (md->version == 1) {