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authorMarcelo Leitner <mleitner@redhat.com>2014-12-11 10:02:22 -0200
committerDavid S. Miller <davem@davemloft.net>2014-12-11 14:57:08 -0500
commit00c83b01d58068dfeb2e1351cca6fccf2a83fa8f (patch)
tree2b00c1d5a6ba84dc4fb9f8c6f9aee3de7aaa6799
parent51f8301485d701caab10e7e9b7f9d7866f2fe3cf (diff)
Fix race condition between vxlan_sock_add and vxlan_sock_release
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@redhat.com> Fixes: 7c47cedf43a8b3 ("vxlan: move IGMP join/leave to work queue") Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/vxlan.c10
1 files changed, 3 insertions, 7 deletions
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 31ecb03368c6..49d9f2291998 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1985,9 +1985,8 @@ static int vxlan_init(struct net_device *dev)
spin_lock(&vn->sock_lock);
vs = vxlan_find_sock(vxlan->net, 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 */
@@ -2389,12 +2388,9 @@ 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)