From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Marcelo Ricardo Leitner , "David S. Miller" Subject: [PATCH 3.14 20/34] Fix race condition between vxlan_sock_add and vxlan_sock_release Date: Sun, 14 Dec 2014 12:20:58 -0800 Message-Id: <20141214201804.382183768@linuxfoundation.org> In-Reply-To: <20141214201803.791392744@linuxfoundation.org> References: <20141214201803.791392744@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Marcelo Leitner [ 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 Fixes: 7c47cedf43a8b3 ("vxlan: move IGMP join/leave to work queue") Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/vxlan.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) --- a/drivers/net/vxlan.c +++ b/drivers/net/vxlan.c @@ -2106,9 +2106,8 @@ static int vxlan_init(struct net_device 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 */ @@ -2574,12 +2573,9 @@ struct vxlan_sock *vxlan_sock_add(struct 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)