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netdev: fix the locking for netdev notifications

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Kuniyuki reports that the assert for netdev lock fires when
there are netdev event listeners (otherwise we skip the netlink
event generation).

Correct the locking when coming from the notifier.

The NETDEV_XDP_FEAT_CHANGE notifier is already fully locked,
it's the documentation that's incorrect.

Fixes: 99e44f39a8 ("netdev: depend on netdev->lock for xdp features")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Reported-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/20250410171019.62128-1-kuniyu@amazon.com
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250416030447.1077551-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2025-04-15 20:04:47 -07:00
parent cfba1d1b61
commit 22cbc1ee26
5 changed files with 27 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

4
Documentation/networking/netdevices.rst
View file

@ -387,12 +387,14 @@ For device drivers that implement shaping or queue management APIs,
some of the notifiers (``enum netdev_cmd``) are running under the netdev
instance lock.
The following netdev notifiers are always run under the instance lock:
* ``NETDEV_XDP_FEAT_CHANGE``
For devices with locked ops, currently only the following notifiers are
running under the lock:
* ``NETDEV_CHANGE``
* ``NETDEV_REGISTER``
* ``NETDEV_UP``
* ``NETDEV_XDP_FEAT_CHANGE``
The following notifiers are running without the lock:
* ``NETDEV_UNREGISTER``

2
include/linux/netdevice.h
View file

@ -2520,7 +2520,7 @@ struct net_device {
* @net_shaper_hierarchy, @reg_state, @threaded
*
* Double protects:
* @up, @moving_ns, @nd_net, @xdp_flags
* @up, @moving_ns, @nd_net, @xdp_features
*
* Double ops protects:
* @real_num_rx_queues, @real_num_tx_queues

16
include/net/netdev_lock.h
View file

@ -48,6 +48,22 @@ static inline void netdev_unlock_ops(struct net_device *dev)
netdev_unlock(dev);
}
static inline void netdev_lock_ops_to_full(struct net_device *dev)
{
if (netdev_need_ops_lock(dev))
netdev_assert_locked(dev);
else
netdev_lock(dev);
}
static inline void netdev_unlock_full_to_ops(struct net_device *dev)
{
if (netdev_need_ops_lock(dev))
netdev_assert_locked(dev);
else
netdev_unlock(dev);
}
static inline void netdev_ops_assert_locked(const struct net_device *dev)
{
if (netdev_need_ops_lock(dev))

4
net/core/lock_debug.c
View file

@ -18,10 +18,12 @@ int netdev_debug_event(struct notifier_block *nb, unsigned long event,
/* Keep enum and don't add default to trigger -Werror=switch */
switch (cmd) {
case NETDEV_XDP_FEAT_CHANGE:
netdev_assert_locked(dev);
fallthrough;
case NETDEV_CHANGE:
case NETDEV_REGISTER:
case NETDEV_UP:
case NETDEV_XDP_FEAT_CHANGE:
netdev_ops_assert_locked(dev);
fallthrough;
case NETDEV_DOWN:

4
net/core/netdev-genl.c
View file

@ -963,10 +963,14 @@ static int netdev_genl_netdevice_event(struct notifier_block *nb,
switch (event) {
case NETDEV_REGISTER:
netdev_lock_ops_to_full(netdev);
netdev_genl_dev_notify(netdev, NETDEV_CMD_DEV_ADD_NTF);
netdev_unlock_full_to_ops(netdev);
break;
case NETDEV_UNREGISTER:
netdev_lock(netdev);
netdev_genl_dev_notify(netdev, NETDEV_CMD_DEV_DEL_NTF);
netdev_unlock(netdev);
break;
case NETDEV_XDP_FEAT_CHANGE:
netdev_genl_dev_notify(netdev, NETDEV_CMD_DEV_CHANGE_NTF);