Commit 971932af authored Dec 10, 2019 by Netanel Belgazal Committed by Greg Kroah-Hartman Jan 04, 2020

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



[ 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: 1738cd3e ("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>

parent b524e0ca

drivers/net/ethernet/amazon/ena/ena_netdev.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -1105,8 +1105,8 @@ static int ena_io_poll(struct napi_struct *napi, int budget)
		struct ena_ring tx_ring, rx_ring;
		struct ena_eth_io_intr_reg intr_reg;

		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;
		@@ -1122,6 +1122,10 @@ static int ena_io_poll(struct napi_struct *napi, int budget)
		}

		tx_work_done = ena_clean_tx_irq(tx_ring, tx_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 ((budget > rx_work_done) && (tx_budget > tx_work_done)) {