net: ena: fix napi handler misbehavior when the napi budget is zero

BugLink: https://bugs.launchpad.net/bugs/1860816
[ Upstream commit 24dee0c7478d1a1e00abdf5625b7f921467325dc ]

In netpoll the napi handler could be called with budget equal to zero.
Current ENA napi handler doesn't take that into consideration.

The napi handler handles Rx packets in a do-while loop.
Currently, the budget check happens only after decrementing the
budget, therefore the napi handler, in rare cases, could run over
MAX_INT packets.

In addition to that, this moves all budget related variables to int
calculation and stop mixing u32 to avoid ambiguity

Fixes: 1738cd3ed342 ("net: ena: Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: Netanel Belgazal <netanel@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index c487d2a7d6dd04cfcc0c5693a6f0692a00753cd9..b4a145220abaef14389eccfd3bcef03d4c7300ef 100644 (file)
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -1238,8 +1238,8 @@ static int ena_io_poll(struct napi_struct *napi, int budget)
        struct ena_napi *ena_napi = container_of(napi, struct ena_napi, napi);
        struct ena_ring *tx_ring, *rx_ring;
 
-       u32 tx_work_done;
-       u32 rx_work_done;
+       int tx_work_done;
+       int rx_work_done = 0;
        int tx_budget;
        int napi_comp_call = 0;
        int ret;
@@ -1256,7 +1256,11 @@ static int ena_io_poll(struct napi_struct *napi, int budget)
        }
 
        tx_work_done = ena_clean_tx_irq(tx_ring, tx_budget);
-       rx_work_done = ena_clean_rx_irq(rx_ring, napi, budget);
+       /* On netpoll the budget is zero and the handler should only clean the
+        * tx completions.
+        */
+       if (likely(budget))
+               rx_work_done = ena_clean_rx_irq(rx_ring, napi, budget);
 
        /* If the device is about to reset or down, avoid unmask
         * the interrupt and return 0 so NAPI won't reschedule