[PATCH 4.19 416/639] mpls: fix warning with multi-label encap

[Greg Kroah-Hartman]

From: George Wilkie <gwilkie@xxxxxxxxxxxxxxxxxxx>

[ Upstream commit 2f3f7d1fa0d1039b24a55d127ed190f196fc3e79 ]

If you configure a route with multiple labels, e.g.
  ip route add 10.10.3.0/24 encap mpls 16/100 via 10.10.2.2 dev ens4
A warning is logged:
  kernel: [  130.561819] netlink: 'ip': attribute type 1 has an invalid
  length.

This happens because mpls_iptunnel_policy has set the type of
MPLS_IPTUNNEL_DST to fixed size NLA_U32.
Change it to a minimum size.
nla_get_labels() does the remaining validation.

Fixes: e3e4712ec096 ("mpls: ip tunnel support")
Signed-off-by: George Wilkie <gwilkie@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: David Ahern <dsahern@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/mpls/mpls_iptunnel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mpls/mpls_iptunnel.c b/net/mpls/mpls_iptunnel.c
index 94f53a9b7d1ae..faf6ef1b6a454 100644
--- a/net/mpls/mpls_iptunnel.c
+++ b/net/mpls/mpls_iptunnel.c
@@ -28,7 +28,7 @@
 #include "internal.h"
 
 static const struct nla_policy mpls_iptunnel_policy[MPLS_IPTUNNEL_MAX + 1] = {
-	[MPLS_IPTUNNEL_DST]	= { .type = NLA_U32 },
+	[MPLS_IPTUNNEL_DST]	= { .len = sizeof(u32) },
 	[MPLS_IPTUNNEL_TTL]	= { .type = NLA_U8 },
 };
 
-- 
2.20.1