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Message-Id: <555533176833d396f82cdcc131e9188286a74b0d.1420799385.git.jslaby@suse.cz>
Date: Fri, 9 Jan 2015 11:31:11 +0100
From: Jiri Slaby <jslaby@...e.cz>
To: stable@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
Marcelo Leitner <mleitner@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 02/78] Fix race condition between vxlan_sock_add and vxlan_sock_release
From: Marcelo Leitner <mleitner@...hat.com>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
[ Upstream commit 00c83b01d58068dfeb2e1351cca6fccf2a83fa8f ]
Currently, when trying to reuse a socket, vxlan_sock_add will grab
vn->sock_lock, locate a reusable socket, inc refcount and release
vn->sock_lock.
But vxlan_sock_release() will first decrement refcount, and then grab
that lock. refcnt operations are atomic but as currently we have
deferred works which hold vs->refcnt each, this might happen, leading to
a use after free (specially after vxlan_igmp_leave):
CPU 1 CPU 2
deferred work vxlan_sock_add
... ...
spin_lock(&vn->sock_lock)
vs = vxlan_find_sock();
vxlan_sock_release
dec vs->refcnt, reaches 0
spin_lock(&vn->sock_lock)
vxlan_sock_hold(vs), refcnt=1
spin_unlock(&vn->sock_lock)
hlist_del_rcu(&vs->hlist);
vxlan_notify_del_rx_port(vs)
spin_unlock(&vn->sock_lock)
So when we look for a reusable socket, we check if it wasn't freed
already before reusing it.
Signed-off-by: Marcelo Ricardo Leitner <mleitner@...hat.com>
Fixes: 7c47cedf43a8b3 ("vxlan: move IGMP join/leave to work queue")
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
drivers/net/vxlan.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 5407c11a9f14..c8e333306c4c 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -2002,9 +2002,8 @@ static int vxlan_init(struct net_device *dev)
spin_lock(&vn->sock_lock);
vs = vxlan_find_sock(dev_net(dev), ipv6 ? AF_INET6 : AF_INET,
vxlan->dst_port);
- if (vs) {
+ if (vs && atomic_add_unless(&vs->refcnt, 1, 0)) {
/* If we have a socket with same port already, reuse it */
- atomic_inc(&vs->refcnt);
vxlan_vs_add_dev(vs, vxlan);
} else {
/* otherwise make new socket outside of RTNL */
@@ -2447,12 +2446,9 @@ struct vxlan_sock *vxlan_sock_add(struct net *net, __be16 port,
spin_lock(&vn->sock_lock);
vs = vxlan_find_sock(net, ipv6 ? AF_INET6 : AF_INET, port);
- if (vs) {
- if (vs->rcv == rcv)
- atomic_inc(&vs->refcnt);
- else
+ if (vs && ((vs->rcv != rcv) ||
+ !atomic_add_unless(&vs->refcnt, 1, 0)))
vs = ERR_PTR(-EBUSY);
- }
spin_unlock(&vn->sock_lock);
if (!vs)
--
2.2.1
--
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