From b2f175648031b8b22927220abd3b081f1a12e628 Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Mon, 8 Feb 2021 14:29:18 -0800 Subject: [PATCH] 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: Alexander Duyck Signed-off-by: David S. Miller --- net/core/net-sysfs.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c index daf502c13d6d..91afb0b6de69 100644 --- a/net/core/net-sysfs.c +++ b/net/core/net-sysfs.c @@ -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; @@ -1158,8 +1165,8 @@ 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) : - sprintf(buf, "%d\n", tc); + return num_tc < 0 ? sprintf(buf, "%d%d\n", tc, num_tc) : + sprintf(buf, "%d\n", tc); } #ifdef CONFIG_XPS