Commit 7e54f85c authored by Antoine Tenart's avatar Antoine Tenart Committed by Jakub Kicinski
Browse files

net-sysfs: prevent uncleared queues from being re-added 



With the (upcoming) removal of the rtnl_trylock/restart_syscall logic
and because of how Tx/Rx queues are implemented (and their
requirements), it might happen that a queue is re-added before having
the chance to be cleared. In such rare case, do not complete the queue
addition operation.

Signed-off-by: default avatarAntoine Tenart <atenart@kernel.org>
Link: https://patch.msgid.link/20250204170314.146022-4-atenart@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent b7ecc1de

net/core/net-sysfs.c

+32 −0
Original line number Diff line number Diff line
@@ -1210,6 +1210,22 @@ static int rx_queue_add_kobject(struct net_device *dev, int index) 
	struct kobject *kobj = &queue->kobj;

	int error = 0;



	/* Rx queues are cleared in rx_queue_release to allow later

	 * re-registration. This is triggered when their kobj refcount is

	 * dropped.

	 *

	 * If a queue is removed while both a read (or write) operation and a

	 * the re-addition of the same queue are pending (waiting on rntl_lock)

	 * it might happen that the re-addition will execute before the read,

	 * making the initial removal to never happen (queue's kobj refcount

	 * won't drop enough because of the pending read). In such rare case,

	 * return to allow the removal operation to complete.

	 */

	if (unlikely(kobj->state_initialized)) {

		netdev_warn_once(dev, "Cannot re-add rx queues before their removal completed");

		return -EAGAIN;

	}



	/* Kobject_put later will trigger rx_queue_release call which

	 * decreases dev refcount: Take that reference here

	 */
@@ -1898,6 +1914,22 @@ static int netdev_queue_add_kobject(struct net_device *dev, int index) 
	struct kobject *kobj = &queue->kobj;

	int error = 0;



	/* Tx queues are cleared in netdev_queue_release to allow later

	 * re-registration. This is triggered when their kobj refcount is

	 * dropped.

	 *

	 * If a queue is removed while both a read (or write) operation and a

	 * the re-addition of the same queue are pending (waiting on rntl_lock)

	 * it might happen that the re-addition will execute before the read,

	 * making the initial removal to never happen (queue's kobj refcount

	 * won't drop enough because of the pending read). In such rare case,

	 * return to allow the removal operation to complete.

	 */

	if (unlikely(kobj->state_initialized)) {

		netdev_warn_once(dev, "Cannot re-add tx queues before their removal completed");

		return -EAGAIN;

	}



	/* Kobject_put later will trigger netdev_queue_release call

	 * which decreases dev refcount: Take that reference here

	 */