[PATCH 3.10 018/139] xfrm: policy: check policy direction value

[Willy Tarreau]

From: Vladis Dronov <vdronov@xxxxxxxxxx>

commit 7bab09631c2a303f87a7eb7e3d69e888673b9b7e upstream.

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@xxxxxxxxxxxxxxx> 
Reported-by: "bo Zhang" <zhangbo5891001@xxxxxxxxx>
Signed-off-by: Vladis Dronov <vdronov@xxxxxxxxxx>
Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 net/xfrm/xfrm_policy.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index ea970b8..10c556e 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -3201,9 +3201,15 @@ 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)) == NULL) {
 		err = -ENOENT;
-- 
2.8.0.rc2.1.gbe9624a