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Commit f92d3180 authored by Cong Wang's avatar Cong Wang Committed by David S. Miller
Browse files

netpoll: fix a rtnl lock assertion failure 



v4: hold rtnl lock for the whole netpoll_setup()
v3: remove the comment
v2: use RCU read lock

This patch fixes the following warning:

[   72.013864] RTNL: assertion failed at net/core/dev.c (4955)
[   72.017758] Pid: 668, comm: netpoll-prep-v6 Not tainted 3.8.0-rc1+ #474
[   72.019582] Call Trace:
[   72.020295]  [<ffffffff8176653d>] netdev_master_upper_dev_get+0x35/0x58
[   72.022545]  [<ffffffff81784edd>] netpoll_setup+0x61/0x340
[   72.024846]  [<ffffffff815d837e>] store_enabled+0x82/0xc3
[   72.027466]  [<ffffffff815d7e51>] netconsole_target_attr_store+0x35/0x37
[   72.029348]  [<ffffffff811c3479>] configfs_write_file+0xe2/0x10c
[   72.030959]  [<ffffffff8115d239>] vfs_write+0xaf/0xf6
[   72.032359]  [<ffffffff81978a05>] ? sysret_check+0x22/0x5d
[   72.033824]  [<ffffffff8115d453>] sys_write+0x5c/0x84
[   72.035328]  [<ffffffff819789d9>] system_call_fastpath+0x16/0x1b

In case of other races, hold rtnl lock for the entire netpoll_setup() function.

Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: default avatarCong Wang <amwang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7db11f75

net/core/netpoll.c

+10 −14
Original line number Diff line number Diff line
@@ -1048,11 +1048,13 @@ int netpoll_setup(struct netpoll *np) 
	struct in_device *in_dev;

	int err;



	rtnl_lock();

	if (np->dev_name)

		ndev = dev_get_by_name(&init_net, np->dev_name);

		ndev = __dev_get_by_name(&init_net, np->dev_name);

	if (!ndev) {

		np_err(np, "%s doesn't exist, aborting\n", np->dev_name);

		return -ENODEV;

		err = -ENODEV;

		goto unlock;

	}



	if (netdev_master_upper_dev_get(ndev)) {
@@ -1066,15 +1068,14 @@ int netpoll_setup(struct netpoll *np) 


		np_info(np, "device %s not up yet, forcing it\n", np->dev_name);



		rtnl_lock();

		err = dev_open(ndev);

		rtnl_unlock();



		if (err) {

			np_err(np, "failed to open %s\n", ndev->name);

			goto put;

		}



		rtnl_unlock();

		atleast = jiffies + HZ/10;

		atmost = jiffies + carrier_timeout * HZ;

		while (!netif_carrier_ok(ndev)) {
@@ -1094,16 +1095,14 @@ int netpoll_setup(struct netpoll *np) 
			np_notice(np, "carrier detect appears untrustworthy, waiting 4 seconds\n");

			msleep(4000);

		}

		rtnl_lock();

	}



	if (!np->local_ip.ip) {

		if (!np->ipv6) {

			rcu_read_lock();

			in_dev = __in_dev_get_rcu(ndev);



			in_dev = __in_dev_get_rtnl(ndev);



			if (!in_dev || !in_dev->ifa_list) {

				rcu_read_unlock();

				np_err(np, "no IP address for %s, aborting\n",

				       np->dev_name);

				err = -EDESTADDRREQ;
@@ -1111,14 +1110,12 @@ int netpoll_setup(struct netpoll *np) 
			}



			np->local_ip.ip = in_dev->ifa_list->ifa_local;

			rcu_read_unlock();

			np_info(np, "local IP %pI4\n", &np->local_ip.ip);

		} else {

#if IS_ENABLED(CONFIG_IPV6)

			struct inet6_dev *idev;



			err = -EDESTADDRREQ;

			rcu_read_lock();

			idev = __in6_dev_get(ndev);

			if (idev) {

				struct inet6_ifaddr *ifp;
@@ -1133,7 +1130,6 @@ int netpoll_setup(struct netpoll *np) 
				}

				read_unlock_bh(&idev->lock);

			}

			rcu_read_unlock();

			if (err) {

				np_err(np, "no IPv6 address for %s, aborting\n",

				       np->dev_name);
@@ -1151,17 +1147,17 @@ int netpoll_setup(struct netpoll *np) 
	/* fill up the skb queue */

	refill_skbs();



	rtnl_lock();

	err = __netpoll_setup(np, ndev, GFP_KERNEL);

	rtnl_unlock();



	if (err)

		goto put;



	rtnl_unlock();

	return 0;



put:

	dev_put(ndev);

unlock:

	rtnl_unlock();

	return err;

}

EXPORT_SYMBOL(netpoll_setup);