[PATCH 4.9 37/51] vsock: lookup and setup guest_cid inside vhost_vsock_lock

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 6c083c2b8a0a110cad936bc0a2c089f0d8115175 ]

Multi vsocks may setup the same cid at the same time.

Signed-off-by: Gao feng <omarapazanadi@xxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/vhost/vsock.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 0ec970ca64ce..6bca57896915 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -50,11 +50,10 @@ static u32 vhost_transport_get_local_cid(void)
 	return VHOST_VSOCK_DEFAULT_HOST_CID;
 }
 
-static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
+static struct vhost_vsock *__vhost_vsock_get(u32 guest_cid)
 {
 	struct vhost_vsock *vsock;
 
-	spin_lock_bh(&vhost_vsock_lock);
 	list_for_each_entry(vsock, &vhost_vsock_list, list) {
 		u32 other_cid = vsock->guest_cid;
 
@@ -63,15 +62,24 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
 			continue;
 
 		if (other_cid == guest_cid) {
-			spin_unlock_bh(&vhost_vsock_lock);
 			return vsock;
 		}
 	}
-	spin_unlock_bh(&vhost_vsock_lock);
 
 	return NULL;
 }
 
+static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
+{
+	struct vhost_vsock *vsock;
+
+	spin_lock_bh(&vhost_vsock_lock);
+	vsock = __vhost_vsock_get(guest_cid);
+	spin_unlock_bh(&vhost_vsock_lock);
+
+	return vsock;
+}
+
 static void
 vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 			    struct vhost_virtqueue *vq)
@@ -607,11 +615,12 @@ static int vhost_vsock_set_cid(struct vhost_vsock *vsock, u64 guest_cid)
 		return -EINVAL;
 
 	/* Refuse if CID is already in use */
-	other = vhost_vsock_get(guest_cid);
-	if (other && other != vsock)
-		return -EADDRINUSE;
-
 	spin_lock_bh(&vhost_vsock_lock);
+	other = __vhost_vsock_get(guest_cid);
+	if (other && other != vsock) {
+		spin_unlock_bh(&vhost_vsock_lock);
+		return -EADDRINUSE;
+	}
 	vsock->guest_cid = guest_cid;
 	spin_unlock_bh(&vhost_vsock_lock);
 
-- 
2.19.1