[PATCH iwl-net v2] idpf: do not perform flow ops when netdev is detached

[Li Li <boolli@google.com>]

Even though commit 2e281e1155fc ("idpf: detach and close netdevs while
handling a reset") prevents ethtool -N/-n operations to operate on
detached netdevs, we found that out-of-tree workflows like OpenOnload
can bypass ethtool core locks and call idpf_set_rxnfc directly during
an idpf HW reset. When this happens, we could get kernel crashes like
the following:

[ 4045.787439] BUG: kernel NULL pointer dereference, address: 0000000000000070
[ 4045.794420] #PF: supervisor read access in kernel mode
[ 4045.799580] #PF: error_code(0x0000) - not-present page
[ 4045.804739] PGD 0
[ 4045.806772] Oops: Oops: 0000 [#1] SMP NOPTI
...
[ 4045.836425] Workqueue: onload-wqueue oof_do_deferred_work_fn [onload]
[ 4045.842926] RIP: 0010:idpf_del_flow_steer+0x24/0x170 [idpf]
...
[ 4045.946323] Call Trace:
[ 4045.948796]  <TASK>
[ 4045.950915]  ? show_trace_log_lvl+0x1b0/0x2f0
[ 4045.955293]  ? show_trace_log_lvl+0x1b0/0x2f0
[ 4045.959672]  ? idpf_set_rxnfc+0x6f/0x80 [idpf]
[ 4046.063613]  </TASK>

To prevent this, we need to add checks in idpf_set_rxnfc and
idpf_get_rxnfc to error out if the netdev is already detached.

Tested: synthetically forced idpf into a HW reset by introducing module
parameters to simulate a Tx timeout and force virtual channel
initialization failure. This was done by skipping completion cleaning for
specific queues and returning -EIO during core initialization.
The failure was then triggered by writing 1 to the corresponding sysfs
parameters and calling idpf_get_rxnfc() during the reset process.

Without the patch: encountered NULL pointer and kernel crash.

With the patch: no crashes.

Fixes: 2e281e1155fc ("idpf: detach and close netdevs while handling a reset")
Cc: stable@vger.kernel.org
Signed-off-by: Li Li <boolli@google.com>
---
v2:
- Removed the raw code block from the commit message and replaced it with
  a textual description of the test modifications.

 drivers/net/ethernet/intel/idpf/idpf_ethtool.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/intel/idpf/idpf_ethtool.c b/drivers/net/ethernet/intel/idpf/idpf_ethtool.c
index bb99d9e7c65d..8368a7e6a754 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_ethtool.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_ethtool.c
@@ -43,6 +43,9 @@ static int idpf_get_rxnfc(struct net_device *netdev, struct ethtool_rxnfc *cmd,
 	unsigned int cnt = 0;
 	int err = 0;
 
+	if (!netdev || !netif_device_present(netdev))
+		return -ENODEV;
+
 	idpf_vport_ctrl_lock(netdev);
 	vport = idpf_netdev_to_vport(netdev);
 	vport_config = np->adapter->vport_config[np->vport_idx];
@@ -349,6 +352,9 @@ static int idpf_set_rxnfc(struct net_device *netdev, struct ethtool_rxnfc *cmd)
 {
 	int ret = -EOPNOTSUPP;
 
+	if (!netdev || !netif_device_present(netdev))
+		return -ENODEV;
+
 	idpf_vport_ctrl_lock(netdev);
 	switch (cmd->cmd) {
 	case ETHTOOL_SRXCLSRLINS:
-- 
2.54.0.rc1.555.g9c883467ad-goog