hv_netvsc: Fix accessing freed memory in netvsc_change_mtu()

struct netvsc_device is freed in rndis_filter_device_remove(). So we save
the nvdev->num_chn into a temp variable for later usage.

(Please also include this patch into stable branch.)

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>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 08608499fa17..b8121eba33ff 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -858,6 +858,7 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
         struct netvsc_device *nvdev = hv_get_drvdata(hdev);
         struct netvsc_device_info device_info;
         int limit = ETH_DATA_LEN;
+        u32 num_chn;
         int ret = 0;
 
         if (nvdev == NULL || nvdev->destroy)
@@ -873,6 +874,8 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
         if (ret)
                 goto out;
 
+        num_chn = nvdev->num_chn;
+
         nvdev->start_remove = true;
         rndis_filter_device_remove(hdev);
 
@@ -883,7 +886,7 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 
         memset(&device_info, 0, sizeof(device_info));
         device_info.ring_size = ring_size;
-        device_info.num_chn = nvdev->num_chn;
+        device_info.num_chn = num_chn;
         device_info.max_num_vrss_chns = max_num_vrss_chns;
         rndis_filter_device_add(hdev, &device_info);