hv_netvsc: fix potential deadlock in netvsc_vf_setxdp()

The MANA driver's probe registers netdevice via the following call chain:

mana_probe()
  register_netdev()
    register_netdevice()

register_netdevice() calls notifier callback for netvsc driver,
holding the netdev mutex via netdev_lock_ops().

Further this netvsc notifier callback end up attempting to acquire the
same lock again in dev_xdp_propagate() leading to deadlock.

netvsc_netdev_event()
  netvsc_vf_setxdp()
    dev_xdp_propagate()

This deadlock was not observed so far because net_shaper_ops was never set,
and thus the lock was effectively a no-op in this case. Fix this by using
netif_xdp_propagate() instead of dev_xdp_propagate() to avoid recursive
locking in this path.

And, since no deadlock is observed on the other path which is via
netvsc_probe, add the lock exclusivly for that path.

Also, clean up the unregistration path by removing the unnecessary call to
netvsc_vf_setxdp(), since unregister_netdevice_many_notify() already
performs this cleanup via dev_xdp_uninstall().

Fixes: 97246d6 ("net: hold netdev instance lock during ndo_bpf")
Cc: [email protected]
Signed-off-by: Saurabh Sengar <[email protected]>
Tested-by: Erni Sri Satya Vennela <[email protected]>
Reviewed-by: Haiyang Zhang <[email protected]>
Reviewed-by: Subbaraya Sundeep <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Saurabh Sengar

drivers/net/hyperv/netvsc_bpf.c

@@ -183,7 +183,7 @@ int netvsc_vf_setxdp(struct net_device *vf_netdev, struct bpf_prog *prog)
 	xdp.command = XDP_SETUP_PROG;
 	xdp.prog = prog;
 
-	ret = dev_xdp_propagate(vf_netdev, &xdp);
+	ret = netif_xdp_propagate(vf_netdev, &xdp);
 
 	if (ret && prog)
 		bpf_prog_put(prog);

drivers/net/hyperv/netvsc_drv.c

@@ -2462,8 +2462,6 @@ static int netvsc_unregister_vf(struct net_device *vf_netdev)
 
 	netdev_info(ndev, "VF unregistering: %s\n", vf_netdev->name);
 
-	netvsc_vf_setxdp(vf_netdev, NULL);
-
 	reinit_completion(&net_device_ctx->vf_add);
 	netdev_rx_handler_unregister(vf_netdev);
 	netdev_upper_dev_unlink(vf_netdev, ndev);
@@ -2631,7 +2629,9 @@ static int netvsc_probe(struct hv_device *dev,
 			continue;
 
 		netvsc_prepare_bonding(vf_netdev);
+		netdev_lock_ops(vf_netdev);
 		netvsc_register_vf(vf_netdev, VF_REG_IN_PROBE);
+		netdev_unlock_ops(vf_netdev);
 		__netvsc_vf_setup(net, vf_netdev);
 		break;
 	}

net/core/dev.c

@@ -9968,6 +9968,7 @@ int netif_xdp_propagate(struct net_device *dev, struct netdev_bpf *bpf)
 
 	return dev->netdev_ops->ndo_bpf(dev, bpf);
 }
+EXPORT_SYMBOL_GPL(netif_xdp_propagate);
 
 u32 dev_xdp_prog_id(struct net_device *dev, enum bpf_xdp_mode mode)
 {