[PATCH net-next 2/3] vsock: fix vsock_dequeue/enqueue_accept race

[Dexuan Cui]

With the current code, when vsock_dequeue_accept() is removing a sock
from the list, nothing prevents vsock_enqueue_accept() from adding a new
sock into the list concurrently. We should add a lock to protect the list.

Signed-off-by: Dexuan Cui <de...@microsoft.com>
Cc: Andy King <ack...@vmware.com>
Cc: Dmitry Torokhov <d...@vmware.com>
Cc: George Zhang <georgezh...@vmware.com>
Cc: Jorgen Hansen <jhan...@vmware.com>
Cc: Reilly Grant <gra...@vmware.com>
Cc: Asias He <as...@redhat.com>
Cc: Stefan Hajnoczi <stefa...@redhat.com>
Cc: Vitaly Kuznetsov <vkuzn...@redhat.com>
Cc: Cathy Avery <cav...@redhat.com>
Cc: K. Y. Srinivasan <k...@microsoft.com>
Cc: Haiyang Zhang <haiya...@microsoft.com>
Cc: Stephen Hemminger <sthem...@microsoft.com>
---
 net/vmw_vsock/af_vsock.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index dfc8c51e..b7b2c66 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -126,6 +126,7 @@ static struct proto vsock_proto = {
 
 static const struct vsock_transport *transport;
 static DEFINE_MUTEX(vsock_register_mutex);
+static DEFINE_SPINLOCK(vsock_accept_queue_lock);
 
 /**** EXPORTS ****/
 
@@ -406,7 +407,10 @@ void vsock_enqueue_accept(struct sock *listener, struct 
sock *connected)
 
        sock_hold(connected);
        sock_hold(listener);
+
+       spin_lock(&vsock_accept_queue_lock);
        list_add_tail(&vconnected->accept_queue, &vlistener->accept_queue);
+       spin_unlock(&vsock_accept_queue_lock);
 }
 EXPORT_SYMBOL_GPL(vsock_enqueue_accept);
 
@@ -423,7 +427,10 @@ static struct sock *vsock_dequeue_accept(struct sock 
*listener)
        vconnected = list_entry(vlistener->accept_queue.next,
                                struct vsock_sock, accept_queue);
 
+       spin_lock(&vsock_accept_queue_lock);
        list_del_init(&vconnected->accept_queue);
+       spin_unlock(&vsock_accept_queue_lock);
+
        sock_put(listener);
        /* The caller will need a reference on the connected socket so we let
         * it call sock_put().
-- 
2.7.4