xfrm: policy: check policy direction value

xfrm: policy: check policy direction value

Orabug: 28256487
CVE: CVE-2017-11600

The 'dir' parameter in xfrm_migrate() is a user-controlled byte which is used
as an array index. This can lead to an out-of-bound access, kernel lockup and
DoS. Add a check for the 'dir' value.

This fixes CVE-2017-11600.

References: https://bugzilla.redhat.com/show_bug.cgi?id=1474928
Fixes: 80c9abaabf42 ("[XFRM]: Extension for dynamic update of endpoint address(es)")
Cc: <stable@vger.kernel.org> # v2.6.21-rc1
Reported-by: "bo Zhang" <zhangbo5891001@gmail.com>
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
(cherry picked from commit 7bab09631c2a303f87a7eb7e3d69e888673b9b7e)
Signed-off-by: Brian Maly <brian.maly@oracle.com>
Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>