[PATCH net v2] ibmvnic: Check for NULL skb's in NAPI poll routine

[Thomas Falcon <tlfalcon@linux.vnet.ibm.com>]

After introduction of commit d0869c0071e4, there were some instances of
RX queue entries from a previous session (before the device was closed
and reopened) returned to the NAPI polling routine. Since the corresponding
socket buffers were freed, this resulted in a panic on reopen. Include
a check for a NULL skb here to avoid this.

Fixes: d0869c0071e4 ("ibmvnic: Clean RX pool buffers during device close")
Signed-off-by: Thomas Falcon <tlfalcon@linux.vnet.ibm.com>
---
v2: Followed David Miller's suggestion to check for a NULL socket buffer
    Originally sent as "ibmvnic: Clean RX pools only during a hard reset"
---
 drivers/net/ethernet/ibm/ibmvnic.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 996f475..1495cb9 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -1901,6 +1901,11 @@ static int ibmvnic_poll(struct napi_struct *napi, int budget)
 			dev_kfree_skb_any(rx_buff->skb);
 			remove_buff_from_pool(adapter, rx_buff);
 			continue;
+		} else if (!rx_buff->skb) {
+			/* free the entry */
+			next->rx_comp.first = 0;
+			remove_buff_from_pool(adapter, rx_buff);
+			continue;
 		}
 
 		length = be32_to_cpu(next->rx_comp.len);
-- 
2.7.5