hv_netvsc: Fix race condition on Multi-Send Data field

In commit 2a04ae8acb14 ("hv_netvsc: remove locking in netvsc_send()"), the
locking for MSD (Multi-Send Data) field was removed. This could cause a
race condition between RNDIS control messages and data packets processing,
because these two types of traffic are not synchronized.
This patch fixes this issue by sending control messages out directly
without reading MSD field.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 02bab9a7c9ff6e292e1c68856a8a34e860267b1b..059fc523160107239d72080cadb1f2e7c0d246df 100644 (file)
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -867,6 +867,14 @@ int netvsc_send(struct hv_device *device,
        packet->send_buf_index = NETVSC_INVALID_INDEX;
        packet->cp_partial = false;
 
+       /* Send control message directly without accessing msd (Multi-Send
+        * Data) field which may be changed during data packet processing.
+        */
+       if (!skb) {
+               cur_send = packet;
+               goto send_now;
+       }
+
        msdp = &net_device->msd[q_idx];
 
        /* batch packets in send buffer if possible */
@@ -939,6 +947,7 @@ int netvsc_send(struct hv_device *device,
                }
        }
 
+send_now:
        if (cur_send)
                ret = netvsc_send_pkt(cur_send, net_device, pb, skb);