[PATCH net-next] net: fix reference tracker mismanagement in netdev_put_lock()

Jakub Kicinski
2026-04-10T15:36:02Z

dev_put() releases a reference which didn't have a tracker.
References without a tracker are accounted in the tracking
code as "no_tracker". We can't free the tracker and then
call dev_put(). The references themselves will be fine
but the tracking code will think it's a double-release:

refcount_t: decrement hit 0; leaking memory.

IOW commit under fixes confused dev_put() (release never tracked
reference) with __dev_put() (just release the reference, skipping
the reference tracking infra).

Since __netdev_put_lock() uses dev_put() we can't feed a previously
tracked netdev ref into it. Let's flip things around.
netdev_put(dev, NULL) is the same as dev_put(dev) so make
netdev_put_lock() the real function and have __netdev_put_lock()
feed it a NULL tracker for all the cases that were untracked.

Fixes: d04686d9bc86 ("net: Implement netdev_nl_queue_create_doit")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: dw@davidwei.uk
CC: skhawaja@google.com
CC: bestswngs@gmail.com
CC: razor@blackwall.org
CC: daniel@iogearbox.net
---
net/core/dev.h | 8 +++++++-
net/core/dev.c | 16 +++++-----------
2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/net/core/dev.h b/net/core/dev.h
index 376bac4a82da..628bdaebf0ca 100644
--- a/net/core/dev.h
+++ b/net/core/dev.h
@@ -31,9 +31,15 @@ struct napi_struct *
netdev_napi_by_id_lock(struct net *net, unsigned int napi_id);
struct net_device *dev_get_by_napi_id(unsigned int napi_id);

-struct net_device *__netdev_put_lock(struct net_device *dev, struct net *net);
struct net_device *netdev_put_lock(struct net_device *dev, struct net *net,
netdevice_tracker *tracker);
+
+static inline struct net_device *
+__netdev_put_lock(struct net_device *dev, struct net *net)
+{
+ return netdev_put_lock(dev, net, NULL);
+}
+
struct net_device *
netdev_xa_find_lock(struct net *net, struct net_device *dev,
unsigned long *index);
diff --git a/net/core/dev.c b/net/core/dev.c
index e7bc95cbd1fa..4a82983e8616 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1060,16 +1060,18 @@ struct net_device *dev_get_by_napi_id(unsigned int napi_id)
* This helper is intended for locking net_device after it has been looked up
* using a lockless lookup helper. Lock prevents the instance from going away.
*/
-struct net_device *__netdev_put_lock(struct net_device *dev, struct net *net)
+struct net_device *
+netdev_put_lock(struct net_device *dev, struct net *net,
+ netdevice_tracker *tracker)
{
netdev_lock(dev);
if (dev->reg_state > NETREG_REGISTERED ||
dev->moving_ns || !net_eq(dev_net(dev), net)) {
netdev_unlock(dev);
- dev_put(dev);
+ netdev_put(dev, tracker);
return NULL;
}
- dev_put(dev);
+ netdev_put(dev, tracker);
return dev;
}

@@ -1121,14 +1123,6 @@ netdev_get_by_index_lock_ops_compat(struct net *net, int ifindex)
return __netdev_put_lock_ops_compat(dev, net);
}

-struct net_device *
-netdev_put_lock(struct net_device *dev, struct net *net,
- netdevice_tracker *tracker)
-{
- netdev_tracker_free(dev, tracker);
- return __netdev_put_lock(dev, net);
-}
-
struct net_device *
netdev_xa_find_lock(struct net *net, struct net_device *dev,
unsigned long *index)
--
2.53.0