netvsc: fix use after free on module removal

The NAPI data structure is embedded in the netvsc_device structure
and is freed when device is closed. There is still a reference
(in NAPI list) to this which causes a crash in netif_napi_del
when device is removed. Fix by managing NAPI instances correctly.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 11 insertions, 7 deletions

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 967843ba03fa..f99651c03e0a 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -584,8 +584,9 @@ void netvsc_device_remove(struct hv_device *device)
         /* Now, we can close the channel safely */
         vmbus_close(device->channel);
 
+        /* And dissassociate NAPI context from device */
         for (i = 0; i < net_device->num_chn; i++)
-                napi_disable(&net_device->chan_table[i].napi);
+                netif_napi_del(&net_device->chan_table[i].napi);
 
         /* Release all resources */
         free_netvsc_device_rcu(net_device);
@@ -1320,8 +1321,6 @@ int netvsc_device_add(struct hv_device *device,
                 struct netvsc_channel *nvchan = &net_device->chan_table[i];
 
                 nvchan->channel = device->channel;
-                netif_napi_add(ndev, &nvchan->napi,
-                               netvsc_poll, NAPI_POLL_WEIGHT);
         }
 
         /* Open the channel */
@@ -1339,6 +1338,8 @@ int netvsc_device_add(struct hv_device *device,
         netdev_dbg(ndev, "hv_netvsc channel opened successfully\n");
 
         /* Enable NAPI handler for init callbacks */
+        netif_napi_add(ndev, &net_device->chan_table[0].napi,
+                       netvsc_poll, NAPI_POLL_WEIGHT);
         napi_enable(&net_device->chan_table[0].napi);
 
         /* Writing nvdev pointer unlocks netvsc_send(), make sure chn_table is
@@ -1357,7 +1358,7 @@ int netvsc_device_add(struct hv_device *device,
         return ret;
 
 close:
-        napi_disable(&net_device->chan_table[0].napi);
+        netif_napi_del(&net_device->chan_table[0].napi);
 
         /* Now, we can close the channel safely */
         vmbus_close(device->channel);
diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
index 1e9445bc4539..ab92c3c95951 100644
--- a/drivers/net/hyperv/rndis_filter.c
+++ b/drivers/net/hyperv/rndis_filter.c
@@ -1009,13 +1009,16 @@ static void netvsc_sc_open(struct vmbus_channel *new_sc)
 
         /* Set the channel before opening.*/
         nvchan->channel = new_sc;
+        netif_napi_add(ndev, &nvchan->napi,
+                       netvsc_poll, NAPI_POLL_WEIGHT);
 
         ret = vmbus_open(new_sc, nvscdev->ring_size * PAGE_SIZE,
                          nvscdev->ring_size * PAGE_SIZE, NULL, 0,
                          netvsc_channel_cb, nvchan);
-
-
-        napi_enable(&nvchan->napi);
+        if (ret == 0)
+                napi_enable(&nvchan->napi);
+        else
+                netdev_err(ndev, "sub channel open failed (%d)\n", ret);
 
         if (refcount_dec_and_test(&nvscdev->sc_offered))
                 complete(&nvscdev->channel_init_wait);