[PATCH 5.5 052/170] net: ip_gre: Accept IFLA_INFO_DATA-less configuration

[Greg Kroah-Hartman]

From: Petr Machata <petrm@xxxxxxxxxxxx>

[ 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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Petr Machata <petrm@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv4/ip_gre.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1168,6 +1168,8 @@ static int erspan_netlink_parms(struct n
 	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]);