Commit b2f17564 authored by Alexander Duyck's avatar Alexander Duyck Committed by David S. Miller
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net-sysfs: Add rtnl locking for getting Tx queue traffic class 



In order to access the suboordinate dev for a device we should be holding
the rtnl_lock when outside of the transmit path. The existing code was not
doing that for the sysfs dump function and as a result we were open to a
possible race.

To resolve that take the rtnl lock prior to accessing the sb_dev field of
the Tx queue and release it after we have retrieved the tc for the queue.

Signed-off-by: default avatarAlexander Duyck <alexanderduyck@fb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 796c9015

net/core/net-sysfs.c

+10 −3
Original line number Diff line number Diff line
@@ -1136,18 +1136,25 @@ static ssize_t traffic_class_show(struct netdev_queue *queue, 
				  char *buf)

{

	struct net_device *dev = queue->dev;

	int num_tc, tc;

	int index;

	int tc;



	if (!netif_is_multiqueue(dev))

		return -ENOENT;



	if (!rtnl_trylock())

		return restart_syscall();



	index = get_netdev_queue_index(queue);



	/* If queue belongs to subordinate dev use its TC mapping */

	dev = netdev_get_tx_queue(dev, index)->sb_dev ? : dev;



	num_tc = dev->num_tc;

	tc = netdev_txq_to_tc(dev, index);



	rtnl_unlock();



	if (tc < 0)

		return -EINVAL;
@@ -1158,7 +1165,7 @@ static ssize_t traffic_class_show(struct netdev_queue *queue, 
	 * belongs to the root device it will be reported with just the

	 * traffic class, so just "0" for TC 0 for example.

	 */

	return dev->num_tc < 0 ? sprintf(buf, "%d%d\n", tc, dev->num_tc) :

	return num_tc < 0 ? sprintf(buf, "%d%d\n", tc, num_tc) :

			    sprintf(buf, "%d\n", tc);

}