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net: designate queue counts as "double ops protected" by instance lock

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Drivers which opt into instance lock protection of ops should
only call set_real_num_*_queues() under the instance lock.
This means that queue counts are double protected (writes
are under both rtnl_lock and instance lock, readers under
either).

Some readers may still be under the rtnl_lock, however, so for
now we need double protection of writers.

OTOH queue API paths are only under the protection of the instance
lock, so we need to validate that the instance is actually locking
ops, otherwise the input checks we do against queue count are racy.

Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250324224537.248800-6-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2025-03-24 15:45:31 -07:00
parent 4b702f8b72
commit 0a65dcf624
5 changed files with 17 additions and 0 deletions
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3
include/linux/netdevice.h
View file

@ -2523,6 +2523,9 @@ struct net_device {
* Double protects:
* @up
*
* Double ops protects:
* @real_num_rx_queues, @real_num_tx_queues
*
* Also protects some fields in struct napi_struct.
*
* Ordering: take after rtnl_lock.

2
net/core/dev.c
View file

@ -3130,6 +3130,7 @@ int netif_set_real_num_tx_queues(struct net_device *dev, unsigned int txq)
if (dev->reg_state == NETREG_REGISTERED ||
dev->reg_state == NETREG_UNREGISTERING) {
ASSERT_RTNL();
netdev_ops_assert_locked(dev);
rc = netdev_queue_update_kobjects(dev, dev->real_num_tx_queues,
txq);
@ -3179,6 +3180,7 @@ int netif_set_real_num_rx_queues(struct net_device *dev, unsigned int rxq)
if (dev->reg_state == NETREG_REGISTERED) {
ASSERT_RTNL();
netdev_ops_assert_locked(dev);
rc = net_rx_queue_update_kobjects(dev, dev->real_num_rx_queues,
rxq);

2
net/core/net-sysfs.c
View file

@ -2148,8 +2148,10 @@ static void remove_queue_kobjects(struct net_device *dev)
net_rx_queue_update_kobjects(dev, real_rx, 0);
netdev_queue_update_kobjects(dev, real_tx, 0);
netdev_lock_ops(dev);
dev->real_num_rx_queues = 0;
dev->real_num_tx_queues = 0;
netdev_unlock_ops(dev);
#ifdef CONFIG_SYSFS
kset_unregister(dev->queues_kset);
#endif

7
net/core/netdev-genl.c
View file

@ -867,6 +867,13 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
goto err_unlock_sock;
}
if (!netdev_need_ops_lock(netdev)) {
err = -EOPNOTSUPP;
NL_SET_BAD_ATTR(info->extack,
info->attrs[NETDEV_A_DEV_IFINDEX]);
goto err_unlock;
}
if (dev_xdp_prog_count(netdev)) {
NL_SET_ERR_MSG(info->extack, "unable to bind dmabuf to device with XDP program attached");
err = -EEXIST;

3
net/core/netdev_rx_queue.c
View file

@ -92,6 +92,9 @@ static int __net_mp_open_rxq(struct net_device *dev, unsigned ifq_idx,
struct netdev_rx_queue *rxq;
int ret;
if (!netdev_need_ops_lock(dev))
return -EOPNOTSUPP;
if (ifq_idx >= dev->real_num_rx_queues)
return -EINVAL;
ifq_idx = array_index_nospec(ifq_idx, dev->real_num_rx_queues);