Commit 47c846eb authored by Jakub Kicinski's avatar Jakub Kicinski Committed by Zheng Zengkai
Browse files

net: make free_netdev() more lenient with unregistering devices 

mainline inclusion
from mainline-v5.11-rc4
commit c269a24c
category: bugfix
bugzilla: 181892 https://gitee.com/openeuler/kernel/issues/I4DDEL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c269a24ce057abfc31130960e96ab197ef6ab196



-------------------------------------------------

There are two flavors of handling netdev registration:
 - ones called without holding rtnl_lock: register_netdev() and
   unregister_netdev(); and
 - those called with rtnl_lock held: register_netdevice() and
   unregister_netdevice().

While the semantics of the former are pretty clear, the same can't
be said about the latter. The netdev_todo mechanism is utilized to
perform some of the device unregistering tasks and it hooks into
rtnl_unlock() so the locked variants can't actually finish the work.
In general free_netdev() does not mix well with locked calls. Most
drivers operating under rtnl_lock set dev->needs_free_netdev to true
and expect core to make the free_netdev() call some time later.

The part where this becomes most problematic is error paths. There is
no way to unwind the state cleanly after a call to register_netdevice(),
since unreg can't be performed fully without dropping locks.

Make free_netdev() more lenient, and defer the freeing if device
is being unregistered. This allows error paths to simply call
free_netdev() both after register_netdevice() failed, and after
a call to unregister_netdevice() but before dropping rtnl_lock.

Simplify the error paths which are currently doing gymnastics
around free_netdev() handling.

Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarXu Jia <xujia39@huawei.com>
Reviewed-by: default avatarYue Haibing <yuehaibing@huawei.com>

Signed-off-by: default avatarChen Jun <chenjun102@huawei.com>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent c0e2ba50

net/8021q/vlan.c

+1 −3
Original line number Diff line number Diff line
@@ -284,8 +284,6 @@ static int register_vlan_device(struct net_device *real_dev, u16 vlan_id) 
	return 0;



out_free_newdev:

	if (new_dev->reg_state == NETREG_UNINITIALIZED ||

	    new_dev->reg_state == NETREG_UNREGISTERED)

	free_netdev(new_dev);

	return err;

}

net/core/dev.c

+11 −0
Original line number Diff line number Diff line
@@ -10655,6 +10655,17 @@ void free_netdev(struct net_device *dev) 
	struct napi_struct *p, *n;



	might_sleep();



	/* When called immediately after register_netdevice() failed the unwind

	 * handling may still be dismantling the device. Handle that case by

	 * deferring the free.

	 */

	if (dev->reg_state == NETREG_UNREGISTERING) {

		ASSERT_RTNL();

		dev->needs_free_netdev = true;

		return;

	}



	netif_free_tx_queues(dev);

	netif_free_rx_queues(dev);

net/core/rtnetlink.c

+6 −17
Original line number Diff line number Diff line
@@ -3438,26 +3438,15 @@ static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh, 


	dev->ifindex = ifm->ifi_index;



	if (ops->newlink) {

	if (ops->newlink)

		err = ops->newlink(link_net ? : net, dev, tb, data, extack);

		/* Drivers should call free_netdev() in ->destructor

		 * and unregister it on failure after registration

		 * so that device could be finally freed in rtnl_unlock.

		 */

		if (err < 0) {

			/* If device is not registered at all, free it now */

			if (dev->reg_state == NETREG_UNINITIALIZED ||

			    dev->reg_state == NETREG_UNREGISTERED)

				free_netdev(dev);

			goto out;

		}

	} else {

	else

		err = register_netdevice(dev);

	if (err < 0) {

		free_netdev(dev);

		goto out;

	}

	}



	err = rtnl_configure_link(dev, ifm);

	if (err < 0)

		goto out_unregister;