linux-kernel - [PATCH 3.16 230/233] xfrm: policy: check policy direction value

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Date:   Sat, 09 Sep 2017 22:47:15 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "bo Zhang" <zhangbo5891001@...il.com>,
        "Steffen Klassert" <steffen.klassert@...unet.com>,
        "Vladis Dronov" <vdronov@...hat.com>
Subject: [PATCH 3.16 230/233] xfrm: policy: check policy direction value

3.16.48-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Vladis Dronov <vdronov@...hat.com>

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)")
Reported-by: "bo Zhang" <zhangbo5891001@...il.com>
Signed-off-by: Vladis Dronov <vdronov@...hat.com>
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/xfrm/xfrm_policy.c | 6 ++++++
 1 file changed, 6 insertions(+)

--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -3123,9 +3123,15 @@ int xfrm_migrate(const struct xfrm_selec
 	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;