From 584661cc24d740bc0d68b605e7089d80a99bba9d Mon Sep 17 00:00:00 2001
From: William Tu <u9012063@gmail.com>
Date: Tue, 12 May 2020 10:36:23 -0700
Subject: erspan: Check IFLA_GRE_ERSPAN_VER is set.

commit 51fa960d3b5163b1af22efdebcabfccc5d615ad6 upstream.

Add a check to make sure the IFLA_GRE_ERSPAN_VER is provided by users.

Fixes: f989d546a2d5 ("erspan: Add type I version 0 support.")
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: William Tu <u9012063@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/ip_gre.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 6d4b6815aa34..086474b09db0 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1182,7 +1182,8 @@ static int erspan_validate(struct nlattr *tb[], struct nlattr *data[],
 	if (ret)
 		return ret;
 
-	if (nla_get_u8(data[IFLA_GRE_ERSPAN_VER]) == 0)
+	if (data[IFLA_GRE_ERSPAN_VER] &&
+	    nla_get_u8(data[IFLA_GRE_ERSPAN_VER]) == 0)
 		return 0;
 
 	/* ERSPAN type II/III should only have GRE sequence and key flag */
-- 
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