[PATCH net-next 1/7] ibmveth: fix netpoll races with RX replenish

[Mingming Cao <mmc@linux.ibm.com>]

ibmveth_poll_controller() runs RX replenish outside NAPI and without
a lock, racing NAPI's replenish on another CPU. Both can fill the
same slot, so an skb and its DMA mapping leak and PHYP can write
into an unmapped buffer. netpoll calls it from netconsole and from
netpoll-enabled bonds.

ibmveth_open() also enables NAPI before the RX resources exist.
ibmveth_change_mtu(), veth_pool_store(), ibmveth_set_csum_offload()
and ibmveth_set_tso() call close() and open() directly, so while
open() is still setting up, netpoll and the direct ibmveth_interrupt()
calls can replenish NULL pools and read freed memory.

Remove the callback, as Eric Dumazet did for many drivers after
commit ac3d9dd034e5 ("netpoll: make ndo_poll_controller() optional"),
including ibmvnic in commit 0c3b9d1b37df ("ibmvnic: remove
ndo_poll_controller"). netpoll then polls NAPI itself with budget 0,
serialized with NAPI by napi->poll_owner. ibmveth_poll() handles
budget 0 and TX completes synchronously, so nothing else is needed.

Enable NAPI just before request_irq(), once everything
ibmveth_poll() touches exists.

Neither race was reproduced. Tested on a POWER10 LPAR with netconsole
over ibmveth: a ping flood (678,470 packets, no loss) during a printk
flood, and MTU changes and buffer pool toggles under traffic, with no
warnings.

Fixes: 6b4223748895 ("[PATCH] ibmveth: Add netpoll function")
Fixes: bea3348eef27 ("[NET]: Make NAPI polling independent of struct net_device objects.")
Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
---
 drivers/net/ethernet/ibm/ibmveth.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
index 73e051d26b9d..aa2300e97081 100644
--- a/drivers/net/ethernet/ibm/ibmveth.c
+++ b/drivers/net/ethernet/ibm/ibmveth.c
@@ -623,8 +623,6 @@ static int ibmveth_open(struct net_device *netdev)
 
 	netdev_dbg(netdev, "open starting\n");
 
-	napi_enable(&adapter->napi);
-
 	for(i = 0; i < IBMVETH_NUM_BUFF_POOLS; i++)
 		rxq_entries += adapter->rx_buff_pool[i].size;
 
@@ -712,10 +710,18 @@ static int ibmveth_open(struct net_device *netdev)
 		}
 	}
 
+	/* NAPI can run as soon as it is enabled, from netpoll during the
+	 * direct close()/open() pairs or from a direct ibmveth_interrupt()
+	 * call, so enable it only once everything ibmveth_poll() touches
+	 * exists.
+	 */
+	napi_enable(&adapter->napi);
+
 	netdev_dbg(netdev, "registering irq 0x%x\n", netdev->irq);
 	rc = request_irq(netdev->irq, ibmveth_interrupt, 0, netdev->name,
 			 netdev);
 	if (rc != 0) {
+		napi_disable(&adapter->napi);
 		netdev_err(netdev, "unable to request irq 0x%x, rc %d\n",
 			   netdev->irq, rc);
 		do {
@@ -763,7 +769,6 @@ static int ibmveth_open(struct net_device *netdev)
 out_free_buffer_list:
 	free_page((unsigned long)adapter->buffer_list_addr);
 out:
-	napi_disable(&adapter->napi);
 	return rc;
 }
 
@@ -1680,14 +1685,6 @@ static int ibmveth_change_mtu(struct net_device *dev, int new_mtu)
 	return -EINVAL;
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-static void ibmveth_poll_controller(struct net_device *dev)
-{
-	ibmveth_replenish_task(netdev_priv(dev));
-	ibmveth_interrupt(dev->irq, dev);
-}
-#endif
-
 /**
  * ibmveth_get_desired_dma - Calculate IO memory desired by the driver
  *
@@ -1789,9 +1786,6 @@ static const struct net_device_ops ibmveth_netdev_ops = {
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_set_mac_address    = ibmveth_set_mac_addr,
 	.ndo_features_check	= ibmveth_features_check,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= ibmveth_poll_controller,
-#endif
 };
 
 static int ibmveth_probe(struct vio_dev *dev, const struct vio_device_id *id)
-- 
2.39.3 (Apple Git-146)