xfrm: policy: check policy direction value

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>

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index ff61d85..6f5a0da 100644 (file)
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -3308,9 +3308,15 @@ int xfrm_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
        struct xfrm_state *x_new[XFRM_MAX_DEPTH];
        struct xfrm_migrate *mp;
 
+       /* Stage 0 - sanity checks */
        if ((err = xfrm_migrate_check(m, num_migrate)) < 0)
                goto out;
 
+       if (dir >= XFRM_POLICY_MAX) {
+               err = -EINVAL;
+               goto out;
+       }
+
        /* Stage 1 - find policy */
        if ((pol = xfrm_migrate_policy_find(sel, dir, type, net)) == NULL) {
                err = -ENOENT;