diff options
| author | Marcelo Leitner <mleitner@redhat.com> | 2014-12-11 10:02:22 -0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-12-11 14:57:08 -0500 |
| commit | 00c83b01d58068dfeb2e1351cca6fccf2a83fa8f (patch) | |
| tree | 2b00c1d5a6ba84dc4fb9f8c6f9aee3de7aaa6799 | |
| parent | 51f8301485d701caab10e7e9b7f9d7866f2fe3cf (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.c | 10 |
1 files changed, 3 insertions, 7 deletions
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c index 31ecb03368c..49d9f229199 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) |