Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
netdev: fix the locking for netdev notifications
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: 99e44f39a8f7 ("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>
+27
-3
+3
-1
Documentation/networking/netdevices.rst
+3
-1
Documentation/networking/netdevices.rst
···
387
387
some of the notifiers (``enum netdev_cmd``) are running under the netdev
388
388
instance lock.
389
389
390
+
The following netdev notifiers are always run under the instance lock:
391
+
* ``NETDEV_XDP_FEAT_CHANGE``
392
+
390
393
For devices with locked ops, currently only the following notifiers are
391
394
running under the lock:
392
395
* ``NETDEV_CHANGE``
393
396
* ``NETDEV_REGISTER``
394
397
* ``NETDEV_UP``
395
-
* ``NETDEV_XDP_FEAT_CHANGE``
396
398
397
399
The following notifiers are running without the lock:
398
400
* ``NETDEV_UNREGISTER``
+1
-1
include/linux/netdevice.h
+1
-1
include/linux/netdevice.h
+16
include/net/netdev_lock.h
+16
include/net/netdev_lock.h
···
48
48
netdev_unlock(dev);
49
49
}
50
50
51
+
static inline void netdev_lock_ops_to_full(struct net_device *dev)
52
+
{
53
+
if (netdev_need_ops_lock(dev))
54
+
netdev_assert_locked(dev);
55
+
else
56
+
netdev_lock(dev);
57
+
}
58
+
59
+
static inline void netdev_unlock_full_to_ops(struct net_device *dev)
60
+
{
61
+
if (netdev_need_ops_lock(dev))
62
+
netdev_assert_locked(dev);
63
+
else
64
+
netdev_unlock(dev);
65
+
}
66
+
51
67
static inline void netdev_ops_assert_locked(const struct net_device *dev)
52
68
{
53
69
if (netdev_need_ops_lock(dev))
+3
-1
net/core/lock_debug.c
+3
-1
net/core/lock_debug.c
···
18
18
19
19
/* Keep enum and don't add default to trigger -Werror=switch */
20
20
switch (cmd) {
21
+
case NETDEV_XDP_FEAT_CHANGE:
22
+
netdev_assert_locked(dev);
23
+
fallthrough;
21
24
case NETDEV_CHANGE:
22
25
case NETDEV_REGISTER:
23
26
case NETDEV_UP:
24
-
case NETDEV_XDP_FEAT_CHANGE:
25
27
netdev_ops_assert_locked(dev);
26
28
fallthrough;
27
29
case NETDEV_DOWN:
+4
net/core/netdev-genl.c
+4
net/core/netdev-genl.c
···
963
963
964
964
switch (event) {
965
965
case NETDEV_REGISTER:
966
+
netdev_lock_ops_to_full(netdev);
966
967
netdev_genl_dev_notify(netdev, NETDEV_CMD_DEV_ADD_NTF);
968
+
netdev_unlock_full_to_ops(netdev);
967
969
break;
968
970
case NETDEV_UNREGISTER:
971
+
netdev_lock(netdev);
969
972
netdev_genl_dev_notify(netdev, NETDEV_CMD_DEV_DEL_NTF);
973
+
netdev_unlock(netdev);
970
974
break;
971
975
case NETDEV_XDP_FEAT_CHANGE:
972
976
netdev_genl_dev_notify(netdev, NETDEV_CMD_DEV_CHANGE_NTF);