[PATCH AUTOSEL for 4.15 65/78] ip_gre: fix potential memory leak in erspan_rcv

[Sasha Levin]

From: Haishuang Yan <yanhaishu...@cmss.chinamobile.com>

[ Upstream commit 50670b6ee9bc4ae8f9ce3112b437987adf273245 ]

If md is NULL, tun_dst must be freed, otherwise it will cause memory
leak.

Fixes: 1a66a836da6 ("gre: add collect_md mode to ERSPAN tunnel")
Cc: William Tu <u9012...@gmail.com>
Signed-off-by: Haishuang Yan <yanhaishu...@cmss.chinamobile.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 net/ipv4/ip_gre.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index e05bca0e61fc..01bbbfe2c2a7 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -303,8 +303,10 @@ static int erspan_rcv(struct sk_buff *skb, struct 
tnl_ptk_info *tpi,
                                return PACKET_REJECT;
 
                        md = ip_tunnel_info_opts(&tun_dst->u.tun_info);
-                       if (!md)
+                       if (!md) {
+                               dst_release((struct dst_entry *)tun_dst);
                                return PACKET_REJECT;
+                       }
 
                        md->index = index;
                        info = &tun_dst->u.tun_info;
-- 
2.14.1