[PATCH v3 0/4] leds: trigger: netdev: fix sysfs_update_group() races

[PATCH v3 0/4] leds: trigger: netdev: fix sysfs_update_group() races

[A. Sverdlin]

From: Alexander Sverdlin <alexander.sverdlin@siemens.com>

The netdev LED trigger refreshes the link_speed attribute group with
sysfs_update_group() from several contexts (the NETDEV_CHANGE notifier,
device_name writes and, indirectly, trigger (de)activation) that share no
common lock.  On a board that emits PHY link events while the trigger is
being (re)armed during boot this is observed as a hard sysfs failure:

  sysfs: cannot create duplicate filename '...green:lan/link_10'
  ...
  led_trigger_set
  led_trigger_write

The window between activate() and device_add_groups() in led_trigger_set()
is narrow, so to reproduce it reliably I artificially widened it with the
debug patch below:

--- a/drivers/leds/led-triggers.c
+++ b/drivers/leds/led-triggers.c
@@ -12,6 +12,7 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/device.h>
+#include <linux/delay.h>
 #include <linux/timer.h>
 #include <linux/rwsem.h>
 #include <linux/leds.h>
@@ -223,6 +224,8 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
                 if (ret)
                         goto err_activate;

+               msleep(5000);
+
                 ret = device_add_groups(led_cdev->dev, trig->groups);
                 if (ret) {
                         dev_err(led_cdev->dev, "Failed to add trigger attributes\n");

With that msleep() in place, writing the trigger while a NETDEV_CHANGE is
delivered from the linkwatch workqueue reproduces the duplicate-filename
splat every time.

The whole series is LOCKDEP-verified.

Changelog:
v3:
- introduced unset_device_name() as a counterpart of set_device_name()
- guard() has been converted to either explicit mutex_lock()/mutex_unlock()
  or scoped_guard()
- rebased onto next-20260925
v2:
- addressed pre-existing issues found by Sashiko (patches 1&2)
- reduced verbosity both in comments and in commit messages
- patch 3 is a combined rework of patches 1&2 from v1
- dropped sync from cancel_delayed_work() (worker now takes the lock)
- https://lore.kernel.org/all/20260921093249.3481413-1-alexander.sverdlin@siemens.com/
v1:
- https://lore.kernel.org/all/20260914132356.807004-1-alexander.sverdlin@siemens.com/


Alexander Sverdlin (4):
  leds: trigger: netdev: Put netdev on activate error path
  leds: trigger: netdev: Access net_dev under trigger_data->lock in the
    worker
  leds: trigger: netdev: Fix sysfs_update_group() races
  leds: trigger: netdev: Serialize mode/interval stores with trigger
    lock

 drivers/leds/trigger/ledtrig-netdev.c | 112 +++++++++++++++++++-------
 1 file changed, 81 insertions(+), 31 deletions(-)

-- 
2.55.0

[PATCH v3 1/4] leds: trigger: netdev: Put netdev on activate error path

[A. Sverdlin]

From: Alexander Sverdlin <alexander.sverdlin@siemens.com>

When hw control is active, set_device_name() takes a reference on the
netdev via dev_get_by_name(). The register_netdevice_notifier() failure
path frees trigger_data without dropping it, leaking the netdev.

Cc: stable@vger.kernel.org
Closes: https://lore.kernel.org/all/20260914140045.B8F4C1F000FF@smtp.kernel.org/
Fixes: 0316cc5629d1 ("leds: trigger: netdev: init mode if hw control already active")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
---
Changelog:
v3:
- introduced unset_device_name() as a counterpart of set_device_name()

 drivers/leds/trigger/ledtrig-netdev.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index 5b0132484594c..e2a6c95a0dc97 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -324,6 +324,13 @@ static int set_device_name(struct led_netdev_data *trigger_data,
 	return 0;
 }
 
+static void unset_device_name(struct led_netdev_data *trigger_data)
+{
+	dev_put(trigger_data->net_dev);
+	trigger_data->net_dev = NULL;
+	trigger_data->device_name[0] = 0;
+}
+
 static ssize_t device_name_store(struct device *dev,
 				 struct device_attribute *attr, const char *buf,
 				 size_t size)
@@ -776,8 +783,10 @@ static int netdev_trig_activate(struct led_classdev *led_cdev)
 	led_set_trigger_data(led_cdev, trigger_data);
 
 	rc = register_netdevice_notifier(&trigger_data->notifier);
-	if (rc)
+	if (rc) {
+		unset_device_name(trigger_data);
 		kfree(trigger_data);
+	}
 
 	return rc;
 }
@@ -790,7 +799,7 @@ static void netdev_trig_deactivate(struct led_classdev *led_cdev)
 
 	cancel_delayed_work_sync(&trigger_data->work);
 
-	dev_put(trigger_data->net_dev);
+	unset_device_name(trigger_data);
 
 	kfree(trigger_data);
 }
-- 
2.55.0

[PATCH v3 2/4] leds: trigger: netdev: Access net_dev under trigger_data->lock in the worker

[A. Sverdlin]

From: Alexander Sverdlin <alexander.sverdlin@siemens.com>

netdev_trig_work() dereferences trigger_data->net_dev without the lock,
while set_device_name() and netdev_trig_notify() dev_put() and replace it
under trigger_data->lock.  On NETDEV_UNREGISTER the worker can run
dev_get_stats() on a netdev being freed (UAF).

Take trigger_data->lock in the worker.  cancel_delayed_work_sync() must
then never run under that lock.

Cc: stable@vger.kernel.org
Closes: https://lore.kernel.org/all/20260914142116.6DAC51F000FF@smtp.kernel.org/
Fixes: 06f502f57d0d ("leds: trigger: Introduce a NETDEV trigger")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
---
Changelog:
v3:
- explicit mutex_lock()/mutex_unlock() instead of guard()

 drivers/leds/trigger/ledtrig-netdev.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index e2a6c95a0dc97..d62a7b0168523 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -683,9 +683,12 @@ static void netdev_trig_work(struct work_struct *work)
 	unsigned long interval;
 	int invert;
 
+	mutex_lock(&trigger_data->lock);
+
 	/* If we dont have a device, insure we are off */
 	if (!trigger_data->net_dev) {
 		led_set_brightness(trigger_data->led_cdev, LED_OFF);
+		mutex_unlock(&trigger_data->lock);
 		return;
 	}
 
@@ -693,8 +696,10 @@ static void netdev_trig_work(struct work_struct *work)
 	if (!test_bit(TRIGGER_NETDEV_TX, &trigger_data->mode) &&
 	    !test_bit(TRIGGER_NETDEV_RX, &trigger_data->mode) &&
 	    !test_bit(TRIGGER_NETDEV_TX_ERR, &trigger_data->mode) &&
-	    !test_bit(TRIGGER_NETDEV_RX_ERR, &trigger_data->mode))
+	    !test_bit(TRIGGER_NETDEV_RX_ERR, &trigger_data->mode)) {
+		mutex_unlock(&trigger_data->lock);
 		return;
+	}
 
 	dev_stats = dev_get_stats(trigger_data->net_dev, &temp);
 	new_activity =
@@ -735,6 +740,8 @@ static void netdev_trig_work(struct work_struct *work)
 
 	schedule_delayed_work(&trigger_data->work,
 			(atomic_read(&trigger_data->interval)*2));
+
+	mutex_unlock(&trigger_data->lock);
 }
 
 static int netdev_trig_activate(struct led_classdev *led_cdev)
-- 
2.55.0

[PATCH v3 3/4] leds: trigger: netdev: Fix sysfs_update_group() races

[A. Sverdlin]

From: Alexander Sverdlin <alexander.sverdlin@siemens.com>

The link_speed attribute group was listed in netdev_led_trigger.groups,
so the LED core creates and destroys it via device_add_groups() /
device_remove_groups() in led_trigger_set() (under trigger_lock), while
the trigger also refreshes it with sysfs_update_group() from
netdev_trig_notify() and device_name writes.  With no shared lock this was
observed as a sysfs splat when the trigger is re-armed during PHY link-up:

  sysfs: cannot create duplicate filename '...green:lan/link_10'

    CPU 0 (led_trigger_set)        CPU 1 (linkwatch workqueue)
    -----------------------        ---------------------------
    activate():
      register_netdevice_notifier()
    .                              netdev_trig_notify(NETDEV_CHANGE):
    .                                sysfs_update_group() creates "link_10"
    device_add_groups()
      creates "link_10"  <- EEXIST!

The mirror case (device_remove_groups() racing the notifier) leaves an
orphaned sysfs file pointing at freed trigger_data, i.e. a UAF.

Manage the group in the trigger: drop it from netdev_led_trigger.groups
and create/destroy it in activate()/deactivate(), so the LED core never
touches it.  The two remaining refreshers, netdev_trig_notify() and
device_name_store(), are serialized against each other by a dedicated
attr_lock, and the is_visible callback takes trigger_data->lock for its
supported_link_modes read.  sysfs_update_group() is never called under
trigger_data->lock, so it cannot deadlock against a concurrent link_*
store that takes that lock.

Cc: stable@vger.kernel.org
Fixes: 06cdca014eca ("leds: trigger: netdev: Display only supported link speed attribute")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
---
Changelog:
v3:
- changed guard() to scoped_guard() and dev_put() to unset_device_name()
v2:
- this patch is a combined rework of patches 1&2 from v1

 drivers/leds/trigger/ledtrig-netdev.c | 74 +++++++++++++++++----------
 1 file changed, 47 insertions(+), 27 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index d62a7b0168523..b27a453bbb859 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -57,6 +57,8 @@
 
 struct led_netdev_data {
 	struct mutex lock;
+	/* Serializes link_speed group refreshes; never taken by attr stores */
+	struct mutex attr_lock;
 
 	struct delayed_work work;
 	struct notifier_block notifier;
@@ -343,8 +345,9 @@ static ssize_t device_name_store(struct device *dev,
 	if (ret < 0)
 		return ret;
 
-	/* Refresh link_speed visibility */
-	sysfs_update_group(&dev->kobj, &netdev_trig_link_speed_attrs_group);
+	/* Serialize the link_speed visibility refresh against netdev_trig_notify() */
+	scoped_guard(mutex, &trigger_data->attr_lock)
+		sysfs_update_group(&dev->kobj, &netdev_trig_link_speed_attrs_group);
 
 	return size;
 }
@@ -551,22 +554,23 @@ static umode_t netdev_trig_link_speed_visible(struct kobject *kobj,
 	 * Stop at the first matching entry as we care only to check if a particular
 	 * speed is supported and not the kind.
 	 */
-	for_each_set_bit(mode, supported_link_modes, __ETHTOOL_LINK_MODE_MASK_NBITS) {
-		struct ethtool_link_ksettings link_ksettings;
-
-		ethtool_params_from_link_mode(&link_ksettings, mode);
-
-		CHECK_LINK_MODE_ATTR(10);
-		CHECK_LINK_MODE_ATTR(100);
-		CHECK_LINK_MODE_ATTR(1000);
-		CHECK_LINK_MODE_ATTR(2500);
-		CHECK_LINK_MODE_ATTR(5000);
-		CHECK_LINK_MODE_ATTR(10000);
-		CHECK_LINK_MODE_ATTR(25000);
-		CHECK_LINK_MODE_ATTR(40000);
-		CHECK_LINK_MODE_ATTR(50000);
-		CHECK_LINK_MODE_ATTR(100000);
-	}
+	scoped_guard(mutex, &trigger_data->lock)
+		for_each_set_bit(mode, supported_link_modes, __ETHTOOL_LINK_MODE_MASK_NBITS) {
+			struct ethtool_link_ksettings link_ksettings;
+
+			ethtool_params_from_link_mode(&link_ksettings, mode);
+
+			CHECK_LINK_MODE_ATTR(10);
+			CHECK_LINK_MODE_ATTR(100);
+			CHECK_LINK_MODE_ATTR(1000);
+			CHECK_LINK_MODE_ATTR(2500);
+			CHECK_LINK_MODE_ATTR(5000);
+			CHECK_LINK_MODE_ATTR(10000);
+			CHECK_LINK_MODE_ATTR(25000);
+			CHECK_LINK_MODE_ATTR(40000);
+			CHECK_LINK_MODE_ATTR(50000);
+			CHECK_LINK_MODE_ATTR(100000);
+		}
 
 	return 0;
 }
@@ -610,7 +614,6 @@ static const struct attribute_group netdev_trig_attrs_group = {
 
 static const struct attribute_group *netdev_trig_groups[] = {
 	&netdev_trig_attrs_group,
-	&netdev_trig_link_speed_attrs_group,
 	NULL,
 };
 
@@ -658,10 +661,6 @@ static int netdev_trig_notify(struct notifier_block *nb,
 		fallthrough;
 	case NETDEV_CHANGE:
 		get_device_state(trigger_data);
-		/* Refresh link_speed visibility */
-		if (evt == NETDEV_CHANGE)
-			sysfs_update_group(&led_cdev->dev->kobj,
-					   &netdev_trig_link_speed_attrs_group);
 		break;
 	}
 
@@ -669,6 +668,12 @@ static int netdev_trig_notify(struct notifier_block *nb,
 
 	mutex_unlock(&trigger_data->lock);
 
+	if (evt == NETDEV_CHANGE) {
+		scoped_guard(mutex, &trigger_data->attr_lock)
+			sysfs_update_group(&led_cdev->dev->kobj,
+					   &netdev_trig_link_speed_attrs_group);
+	}
+
 	return NOTIFY_DONE;
 }
 
@@ -756,6 +761,7 @@ static int netdev_trig_activate(struct led_classdev *led_cdev)
 		return -ENOMEM;
 
 	mutex_init(&trigger_data->lock);
+	mutex_init(&trigger_data->attr_lock);
 
 	trigger_data->notifier.notifier_call = netdev_trig_notify;
 	trigger_data->notifier.priority = 10;
@@ -789,12 +795,23 @@ static int netdev_trig_activate(struct led_classdev *led_cdev)
 
 	led_set_trigger_data(led_cdev, trigger_data);
 
+	rc = sysfs_create_group(&led_cdev->dev->kobj,
+				&netdev_trig_link_speed_attrs_group);
+	if (rc)
+		goto err_free;
+
 	rc = register_netdevice_notifier(&trigger_data->notifier);
-	if (rc) {
-		unset_device_name(trigger_data);
-		kfree(trigger_data);
-	}
+	if (rc)
+		goto err_remove_group;
+
+	return 0;
 
+err_remove_group:
+	sysfs_remove_group(&led_cdev->dev->kobj,
+			   &netdev_trig_link_speed_attrs_group);
+err_free:
+	unset_device_name(trigger_data);
+	kfree(trigger_data);
 	return rc;
 }
 
@@ -804,6 +821,9 @@ static void netdev_trig_deactivate(struct led_classdev *led_cdev)
 
 	unregister_netdevice_notifier(&trigger_data->notifier);
 
+	sysfs_remove_group(&led_cdev->dev->kobj,
+			   &netdev_trig_link_speed_attrs_group);
+
 	cancel_delayed_work_sync(&trigger_data->work);
 
 	unset_device_name(trigger_data);
-- 
2.55.0

[PATCH v3 4/4] leds: trigger: netdev: Serialize mode/interval stores with trigger lock

[A. Sverdlin]

From: Alexander Sverdlin <alexander.sverdlin@siemens.com>

netdev_led_attr_store() and interval_store() update ->mode and run
set_baseline_state() without trigger_data->lock.  kernfs only serializes
writes to the same file, so two attribute writes race on the non-atomic
read-modify-write of ->mode:

  CPU0 (echo 1 > link_10)       CPU1 (echo 1 > link_100)
  -----------------------       ------------------------
  mode = trigger_data->mode;
                                mode = trigger_data->mode;
  set_bit(LINK_10, &mode);
                                set_bit(LINK_100, &mode);
  trigger_data->mode = mode;
                                trigger_data->mode = mode;  // LINK_10 lost

They also race the notifier's link-state and ->hw_control updates.

Take trigger_data->lock in both stores.  netdev_trig_work() also holds it,
so use the async cancel_delayed_work() (a sync cancel would deadlock).

Cc: stable@vger.kernel.org
Fixes: d5e01266e7f5 ("leds: trigger: netdev: add additional specific link speed mode")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
---
Changelog:
v3:
- explicit mutex_lock()/mutex_unlock() instead of guard()
v2:
- reduced verbosity both in the comments and in commit message
- dropped sync from cancel_delayed_work() (worker now takes the lock)

 drivers/leds/trigger/ledtrig-netdev.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index b27a453bbb859..7ad61c4be282e 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -392,7 +392,7 @@ static ssize_t netdev_led_attr_store(struct device *dev, const char *buf,
 {
 	struct led_netdev_data *trigger_data = led_trigger_get_drvdata(dev);
 	struct led_classdev *led_cdev = trigger_data->led_cdev;
-	unsigned long state, mode = trigger_data->mode;
+	unsigned long state, mode;
 	int ret;
 	int bit;
 
@@ -424,6 +424,10 @@ static ssize_t netdev_led_attr_store(struct device *dev, const char *buf,
 		return -EINVAL;
 	}
 
+	/* async cancel: the worker takes this lock */
+	mutex_lock(&trigger_data->lock);
+
+	mode = trigger_data->mode;
 	assign_bit(bit, &mode, state);
 
 	if (test_bit(TRIGGER_NETDEV_LINK, &mode) &&
@@ -436,20 +440,26 @@ static ssize_t netdev_led_attr_store(struct device *dev, const char *buf,
 	     test_bit(TRIGGER_NETDEV_LINK_25000, &mode) ||
 	     test_bit(TRIGGER_NETDEV_LINK_40000, &mode) ||
 	     test_bit(TRIGGER_NETDEV_LINK_50000, &mode) ||
-	     test_bit(TRIGGER_NETDEV_LINK_100000, &mode)))
+	     test_bit(TRIGGER_NETDEV_LINK_100000, &mode))) {
+		mutex_unlock(&trigger_data->lock);
 		return -EINVAL;
+	}
 
-	cancel_delayed_work_sync(&trigger_data->work);
+	cancel_delayed_work(&trigger_data->work);
 
 	trigger_data->mode = mode;
 	trigger_data->hw_control = can_hw_control(trigger_data);
 
 	if (!led_cdev->brightness_set && !led_cdev->brightness_set_blocking &&
-	    !trigger_data->hw_control)
+	    !trigger_data->hw_control) {
+		mutex_unlock(&trigger_data->lock);
 		return -EOPNOTSUPP;
+	}
 
 	set_baseline_state(trigger_data);
 
+	mutex_unlock(&trigger_data->lock);
+
 	return size;
 }
 
@@ -510,10 +520,14 @@ static ssize_t interval_store(struct device *dev,
 
 	/* impose some basic bounds on the timer interval */
 	if (value >= 5 && value <= 10000) {
-		cancel_delayed_work_sync(&trigger_data->work);
+		mutex_lock(&trigger_data->lock);
+
+		cancel_delayed_work(&trigger_data->work);
 
 		atomic_set(&trigger_data->interval, msecs_to_jiffies(value));
 		set_baseline_state(trigger_data);	/* resets timer */
+
+		mutex_unlock(&trigger_data->lock);
 	}
 
 	return size;
-- 
2.55.0