From 0e792e07ba0769846bdcd88b5a8f9b270561bdb1 Mon Sep 17 00:00:00 2001
From: Petr Machata <petrm@mellanox.com>
Date: Tue, 22 Sep 2020 10:14:06 +0800
Subject: [PATCH] net: ip_gre: Accept IFLA_INFO_DATA-less configuration

stable inclusion
from linux-4.19.114
commit f5ebb2dd86777379a552acce0d635de8210a427c

--------------------------------

[ Upstream commit 32ca98feab8c9076c89c0697c5a85e46fece809d ]

The fix referenced below causes a crash when an ERSPAN tunnel is created
without passing IFLA_INFO_DATA. Fix by validating passed-in data in the
same way as ipgre does.

Fixes: e1f8f78ffe98 ("net: ip_gre: Separate ERSPAN newlink / changelink callbacks")
Reported-by: syzbot+1b4ebf4dae4e510dd219@syzkaller.appspotmail.com
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Li Aichun <liaichun@huawei.com>
Reviewed-by:  guodeqing <geffrey.guo@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 net/ipv4/ip_gre.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 26dfcf605ec5..ffcb5983107d 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1241,6 +1241,8 @@ static int erspan_netlink_parms(struct net_device *dev,
 	err = ipgre_netlink_parms(dev, data, tb, parms, fwmark);
 	if (err)
 		return err;
+	if (!data)
+		return 0;
 
 	if (data[IFLA_GRE_ERSPAN_VER]) {
 		t->erspan_ver = nla_get_u8(data[IFLA_GRE_ERSPAN_VER]);
-- 
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