[PATCH net] sfc: pass valid pointers from efx_enqueue_unwind

[Bert Kenward]

The bytes_compl and pkts_compl pointers passed to efx_dequeue_buffers
cannot be NULL. Add a paranoid warning to check this condition and fix
the one case where they were NULL.

efx_enqueue_unwind() is called very rarely, during error handling.
Without this fix it would fail with a NULL pointer dereference in
efx_dequeue_buffer, with efx_enqueue_skb in the call stack.

Fixes: e9117e5099ea ("sfc: Firmware-Assisted TSO version 2")
Reported-by: Jarod Wilson <ja...@redhat.com>
Signed-off-by: Bert Kenward <bkenw...@solarflare.com>
---
 drivers/net/ethernet/sfc/tx.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c
index 0ea7e16f2e6e..9937a2450e57 100644
--- a/drivers/net/ethernet/sfc/tx.c
+++ b/drivers/net/ethernet/sfc/tx.c
@@ -77,6 +77,7 @@ static void efx_dequeue_buffer(struct efx_tx_queue *tx_queue,
        }
 
        if (buffer->flags & EFX_TX_BUF_SKB) {
+               EFX_WARN_ON_PARANOID(!pkts_compl || !bytes_compl);
                (*pkts_compl)++;
                (*bytes_compl) += buffer->skb->len;
                dev_consume_skb_any((struct sk_buff *)buffer->skb);
@@ -426,12 +427,14 @@ static int efx_tx_map_data(struct efx_tx_queue *tx_queue, 
struct sk_buff *skb,
 static void efx_enqueue_unwind(struct efx_tx_queue *tx_queue)
 {
        struct efx_tx_buffer *buffer;
+       unsigned int bytes_compl = 0;
+       unsigned int pkts_compl = 0;
 
        /* Work backwards until we hit the original insert pointer value */
        while (tx_queue->insert_count != tx_queue->write_count) {
                --tx_queue->insert_count;
                buffer = __efx_tx_queue_get_insert_buffer(tx_queue);
-               efx_dequeue_buffer(tx_queue, buffer, NULL, NULL);
+               efx_dequeue_buffer(tx_queue, buffer, &pkts_compl, &bytes_compl);
        }
 }
 
-- 
2.13.6