netvsc: fix race during initialization

When device is being setup on boot, there is a small race where
network device callback is registered, but the netvsc_device pointer
is not set yet.  This can cause a NULL ptr dereference if packet
arrives during this window.

Fixes: 46b4f7f5d1f7 ("netvsc: eliminate per-device outstanding send counter")
Signed-off-by: Stephen Hemminger <sthemmin@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 4c1d8cc..8dd0b87 100644 (file)
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -1231,8 +1231,11 @@ void netvsc_channel_cb(void *context)
                return;
 
        net_device = net_device_to_netvsc_device(ndev);
-       if (unlikely(net_device->destroy) &&
-           netvsc_channel_idle(net_device, q_idx))
+       if (unlikely(!net_device))
+               return;
+
+       if (unlikely(net_device->destroy &&
+                    netvsc_channel_idle(net_device, q_idx)))
                return;
 
        /* commit_rd_index() -> hv_signal_on_read() needs this. */