[PATCH net v1 3/4] octeon_ep_vf: fix race conditions in ndo_get_stats64

[Shinas Rasheed <srasheed@marvell.com>]

ndo_get_stats64() can race with ndo_stop(), which frees input and
output queue resources. Implement device state variable to protect
against such resource usage.

Fixes: c3fad23cdc06 ("octeon_ep_vf: add support for ndo ops")
Signed-off-by: Shinas Rasheed <srasheed@marvell.com>
---
 .../marvell/octeon_ep_vf/octep_vf_main.c      | 29 +++++++++++++++++++
 .../marvell/octeon_ep_vf/octep_vf_main.h      |  9 ++++++
 2 files changed, 38 insertions(+)

diff --git a/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_main.c b/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_main.c
index 7e6771c9cdbb..12b95fb21e64 100644
--- a/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_main.c
+++ b/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_main.c
@@ -497,6 +497,8 @@ static int octep_vf_open(struct net_device *netdev)
 	if (ret)
 		octep_vf_link_up(netdev);
 
+	set_bit(OCTEP_VF_DEV_STATE_OPEN, &oct->state);
+
 	return 0;
 
 set_queues_err:
@@ -511,6 +513,11 @@ static int octep_vf_open(struct net_device *netdev)
 	return -1;
 }
 
+static bool octep_vf_drv_busy(struct octep_vf_device *oct)
+{
+	return test_bit(OCTEP_VF_DEV_STATE_READ_STATS, &oct->state);
+}
+
 /**
  * octep_vf_stop() - stop the octeon network device.
  *
@@ -525,6 +532,14 @@ static int octep_vf_stop(struct net_device *netdev)
 
 	netdev_info(netdev, "Stopping the device ...\n");
 
+	clear_bit(OCTEP_VF_DEV_STATE_OPEN, &oct->state);
+	/* Make sure device state open is cleared so that no more
+	 * stats fetch can happen intermittently
+	 */
+	smp_mb__after_atomic();
+	while (octep_vf_drv_busy(oct))
+		msleep(20);
+
 	/* Stop Tx from stack */
 	netif_carrier_off(netdev);
 	netif_tx_disable(netdev);
@@ -782,6 +797,16 @@ static void octep_vf_get_stats64(struct net_device *netdev,
 	u64 tx_packets, tx_bytes, rx_packets, rx_bytes;
 	int q;
 
+	set_bit(OCTEP_VF_DEV_STATE_READ_STATS, &oct->state);
+	/* Make sure read stats state is set, so that ndo_stop
+	 * doesn't clear resources as they are read
+	 */
+	smp_mb__after_atomic();
+	if (!test_bit(OCTEP_VF_DEV_STATE_OPEN, &oct->state)) {
+		clear_bit(OCTEP_VF_DEV_STATE_READ_STATS, &oct->state);
+		return;
+	}
+
 	tx_packets = 0;
 	tx_bytes = 0;
 	rx_packets = 0;
@@ -807,6 +832,7 @@ static void octep_vf_get_stats64(struct net_device *netdev,
 		stats->rx_missed_errors = oct->iface_rx_stats.dropped_pkts_fifo_full;
 		stats->tx_dropped = oct->iface_tx_stats.dropped;
 	}
+	clear_bit(OCTEP_VF_DEV_STATE_READ_STATS, &oct->state);
 }
 
 /**
@@ -1140,6 +1166,9 @@ static int octep_vf_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 		dev_err(&pdev->dev, "Failed to register netdev\n");
 		goto delete_mbox;
 	}
+
+	clear_bit(OCTEP_VF_DEV_STATE_OPEN, &octep_vf_dev->state);
+
 	dev_info(&pdev->dev, "Device probe successful\n");
 	return 0;
 
diff --git a/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_main.h b/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_main.h
index 5769f62545cd..692b3bf94722 100644
--- a/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_main.h
+++ b/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_main.h
@@ -213,6 +213,12 @@ struct octep_vf_fw_info {
 	u16 tx_ol_flags;
 };
 
+/* Device state */
+enum octep_vf_dev_state {
+	OCTEP_VF_DEV_STATE_OPEN,
+	OCTEP_VF_DEV_STATE_READ_STATS,
+};
+
 /* The Octeon device specific private data structure.
  * Each Octeon device has this structure to represent all its components.
  */
@@ -282,6 +288,9 @@ struct octep_vf_device {
 	/* offset for iface stats */
 	u32 ctrl_mbox_ifstats_offset;
 
+	/* Device state */
+	unsigned long state;
+
 	/* Negotiated Mbox version */
 	u32 mbox_neg_ver;
 
-- 
2.25.1