netdev - [PATCH net] net: ip_gre: Accept IFLA_INFO

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Date:   Mon, 16 Mar 2020 19:53:00 +0200
From:   Petr Machata <petrm@...lanox.com>
To:     netdev@...r.kernel.org
Cc:     Petr Machata <petrm@...lanox.com>, William Tu <u9012063@...il.com>,
        Xin Long <lucien.xin@...il.com>,
        "David S . Miller" <davem@...emloft.net>, kuznet@....inr.ac.ru,
        syzkaller-bugs@...glegroups.com, yoshfuji@...ux-ipv6.org,
        syzbot+1b4ebf4dae4e510dd219@...kaller.appspotmail.com
Subject: [PATCH net] net: ip_gre: Accept IFLA_INFO_DATA-less configuration

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@...kaller.appspotmail.com
Signed-off-by: Petr Machata <petrm@...lanox.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 7765c65fc7d2..029b24eeafba 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1168,6 +1168,8 @@ 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]);
-- 
2.20.1