[PATCH v2 3/8] vsock/virtio: fix locking for fwd_cnt and buf_alloc

[Stefano Garzarella <sgarzare@redhat.com>]

fwd_cnt is written with rx_lock, so we should read it using
the same spinlock also if we are in the TX path.

Move also buf_alloc under rx_lock and add a missing locking
when we modify it.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 include/linux/virtio_vsock.h            | 2 +-
 net/vmw_vsock/virtio_transport_common.c | 6 ++++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 345f04ee9193..fb5954fc85c8 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -35,11 +35,11 @@ struct virtio_vsock_sock {
 
 	/* Protected by tx_lock */
 	u32 tx_cnt;
-	u32 buf_alloc;
 	u32 peer_fwd_cnt;
 	u32 peer_buf_alloc;
 
 	/* Protected by rx_lock */
+	u32 buf_alloc;
 	u32 fwd_cnt;
 	u32 rx_bytes;
 	struct list_head rx_queue;
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 65c8b4a23f2b..f2e4e128bc86 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -246,10 +246,10 @@ static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs, u32 len)
 
 void virtio_transport_inc_tx_pkt(struct virtio_vsock_sock *vvs, struct virtio_vsock_pkt *pkt)
 {
-	spin_lock_bh(&vvs->tx_lock);
+	spin_lock_bh(&vvs->rx_lock);
 	pkt->hdr.fwd_cnt = cpu_to_le32(vvs->fwd_cnt);
 	pkt->hdr.buf_alloc = cpu_to_le32(vvs->buf_alloc);
-	spin_unlock_bh(&vvs->tx_lock);
+	spin_unlock_bh(&vvs->rx_lock);
 }
 EXPORT_SYMBOL_GPL(virtio_transport_inc_tx_pkt);
 
@@ -469,7 +469,9 @@ void virtio_transport_set_buffer_size(struct vsock_sock *vsk, u64 val)
 	if (val > vvs->buf_size_max)
 		vvs->buf_size_max = val;
 	vvs->buf_size = val;
+	spin_lock_bh(&vvs->rx_lock);
 	vvs->buf_alloc = val;
+	spin_unlock_bh(&vvs->rx_lock);
 }
 EXPORT_SYMBOL_GPL(virtio_transport_set_buffer_size);
 
-- 
2.20.1