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

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 <decui@microsoft.com>
Cc: Andy King <acking@vmware.com>
Cc: Dmitry Torokhov <dtor@vmware.com>
Cc: George Zhang <georgezhang@vmware.com>
Cc: Jorgen Hansen <jhansen@vmware.com>
Cc: Reilly Grant <grantr@vmware.com>
Cc: Asias He <asias@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Cathy Avery <cavery@redhat.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@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
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