linux-kernel - [PATCH 4.9 006/119] vxlan: fix use-after-free on deletion

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Message-Id: <20170612152556.943935493@linuxfoundation.org>
Date:   Mon, 12 Jun 2017 17:24:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jiri Benc <jbenc@...hat.com>,
        Roi Dayan <roid@...lanox.com>, Mark Bloch <markb@...lanox.com>,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.9 006/119] vxlan: fix use-after-free on deletion

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Mark Bloch <markb@...lanox.com>


[ Upstream commit a53cb29b0af346af44e4abf13d7e59f807fba690 ]

Adding a vxlan interface to a socket isn't symmetrical, while adding
is done in vxlan_open() the deletion is done in vxlan_dellink().
This can cause a use-after-free error when we close the vxlan
interface before deleting it.

We add vxlan_vs_del_dev() to match vxlan_vs_add_dev() and call
it from vxlan_stop() to match the call from vxlan_open().

Fixes: 56ef9c909b40 ("vxlan: Move socket initialization to within rtnl scope")
Acked-by: Jiri Benc <jbenc@...hat.com>
Tested-by: Roi Dayan <roid@...lanox.com>
Signed-off-by: Mark Bloch <markb@...lanox.com>
Acked-by: Roopa Prabhu <roopa@...ulusnetworks.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/vxlan.c |   19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -59,6 +59,8 @@ static const u8 all_zeros_mac[ETH_ALEN +
 
 static int vxlan_sock_add(struct vxlan_dev *vxlan);
 
+static void vxlan_vs_del_dev(struct vxlan_dev *vxlan);
+
 /* per-network namespace private data for this module */
 struct vxlan_net {
 	struct list_head  vxlan_list;
@@ -1040,6 +1042,8 @@ static void vxlan_sock_release(struct vx
 	rcu_assign_pointer(vxlan->vn4_sock, NULL);
 	synchronize_net();
 
+	vxlan_vs_del_dev(vxlan);
+
 	if (__vxlan_sock_release_prep(sock4)) {
 		udp_tunnel_sock_release(sock4->sock);
 		kfree(sock4);
@@ -2300,6 +2304,15 @@ static void vxlan_cleanup(unsigned long
 	mod_timer(&vxlan->age_timer, next_timer);
 }
 
+static void vxlan_vs_del_dev(struct vxlan_dev *vxlan)
+{
+	struct vxlan_net *vn = net_generic(vxlan->net, vxlan_net_id);
+
+	spin_lock(&vn->sock_lock);
+	hlist_del_init_rcu(&vxlan->hlist);
+	spin_unlock(&vn->sock_lock);
+}
+
 static void vxlan_vs_add_dev(struct vxlan_sock *vs, struct vxlan_dev *vxlan)
 {
 	struct vxlan_net *vn = net_generic(vxlan->net, vxlan_net_id);
@@ -3070,12 +3083,6 @@ static int vxlan_newlink(struct net *src
 static void vxlan_dellink(struct net_device *dev, struct list_head *head)
 {
 	struct vxlan_dev *vxlan = netdev_priv(dev);
-	struct vxlan_net *vn = net_generic(vxlan->net, vxlan_net_id);
-
-	spin_lock(&vn->sock_lock);
-	if (!hlist_unhashed(&vxlan->hlist))
-		hlist_del_rcu(&vxlan->hlist);
-	spin_unlock(&vn->sock_lock);
 
 	gro_cells_destroy(&vxlan->gro_cells);
 	list_del(&vxlan->next);