mpls: Properly validate RTA_VIA payload length
mpls: Properly validate RTA_VIA payload length

If the nla length is less than 2 then the nla data could be accessed
beyond the accessible bounds. So ensure that the nla is big enough to
at least read the via_family before doing so. Replace magic value of
2.

Fixes: 03c0566542f4 ("mpls: Basic support for adding and removing routes")
Cc: Eric W. Biederman <8a741aa8cbd77ebc4a56ddb528ce9fd15d42f034@xmission.com>
Signed-off-by: Robert Shearman <bc22f500b863056f9f84832d392f90be0c9a9a11@brocade.com>
Acked-by: "Eric W. Biederman" <8a741aa8cbd77ebc4a56ddb528ce9fd15d42f034@xmission.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs