[PATCH v6 0/5] leds: trigger: netdev: fix sysfs_update_group() races

[PATCH v6 0/5] 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:
v6:
- report invalid interval to user space
- fixed unlocked hw_control check in interval_store()
- added missing carrier_link_up check in netdev_trig_sw_blink()
v5:
- removed unset_device_name()
- https://lore.kernel.org/all/20261020124651.1987272-1-alexander.sverdlin@siemens.com/
v4:
- introduced netdev_trig_sw_blink() and used it in netdev_trig_work()
- https://lore.kernel.org/all/20261001131206.2513248-1-alexander.sverdlin@siemens.com/
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
- https://lore.kernel.org/all/20260929120902.2793138-1-alexander.sverdlin@siemens.com/
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 (5):
  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: Report invalid interval to user space
  leds: trigger: netdev: Serialize mode/interval stores with trigger
    lock

 drivers/leds/trigger/ledtrig-netdev.c | 140 ++++++++++++++++++--------
 1 file changed, 96 insertions(+), 44 deletions(-)

-- 
2.56.0

[PATCH v6 1/5] 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:
v5:
- removed unset_device_name()
v3:
- introduced unset_device_name() as a counterpart of set_device_name()

 drivers/leds/trigger/ledtrig-netdev.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index 5b0132484594c..cfaf130157b3d 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -776,8 +776,10 @@ 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) {
+		dev_put(trigger_data->net_dev);
 		kfree(trigger_data);
+	}
 
 	return rc;
 }
-- 
2.56.0

Re: [PATCH v6 1/5] leds: trigger: netdev: Put netdev on activate error path

[sashiko-bot]

> 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>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261027113349.383147-1-alexander.sverdlin@siemens.com?part=1

[PATCH v6 2/5] 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 cfaf130157b3d..e72e850e0070f 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -676,9 +676,12 @@ 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;
 	}
 
@@ -686,8 +689,10 @@ 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 =
@@ -728,6 +733,8 @@ 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)
-- 
2.56.0

Re: [PATCH v6 2/5] leds: trigger: netdev: Access net_dev under trigger_data->lock in the worker

[sashiko-bot]

> 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>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261027113349.383147-1-alexander.sverdlin@siemens.com?part=2

[PATCH v6 3/5] 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 e72e850e0070f..bf9a5ec245a43 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;
@@ -336,8 +338,9 @@ 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;
 }
@@ -544,22 +547,23 @@ 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;
 }
@@ -603,7 +607,6 @@ 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,
 };
 
@@ -651,10 +654,6 @@ 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;
 	}
 
@@ -662,6 +661,12 @@ 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;
 }
 
@@ -749,6 +754,7 @@ 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;
@@ -782,12 +788,23 @@ 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) {
-		dev_put(trigger_data->net_dev);
-		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:
+	dev_put(trigger_data->net_dev);
+	kfree(trigger_data);
 	return rc;
 }
 
@@ -797,6 +814,9 @@ 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);
 
 	dev_put(trigger_data->net_dev);
-- 
2.56.0

Re: [PATCH v6 3/5] leds: trigger: netdev: Fix sysfs_update_group() races

[sashiko-bot]

> 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()
> [ ... ]
> 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>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261027113349.383147-1-alexander.sverdlin@siemens.com?part=3

[PATCH v6 4/5] leds: trigger: netdev: Report invalid interval to user space

[A. Sverdlin]

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

interval_store() silently accepts out-of-range values: a write outside
the [5, 10000] ms bounds returns the full count as if it succeeded, yet
the interval is left unchanged.

Reject out-of-range values with -EINVAL instead.

Cc: stable@vger.kernel.org
Fixes: 06f502f57d0d ("leds: trigger: Introduce a NETDEV trigger")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
---
Changelog:
v6:
- patch introduced

 drivers/leds/trigger/ledtrig-netdev.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index bf9a5ec245a43..b1f84014acab9 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -502,12 +502,13 @@ static ssize_t interval_store(struct device *dev,
 		return ret;
 
 	/* impose some basic bounds on the timer interval */
-	if (value >= 5 && value <= 10000) {
-		cancel_delayed_work_sync(&trigger_data->work);
+	if (value < 5 || value > 10000)
+		return -EINVAL;
 
-		atomic_set(&trigger_data->interval, msecs_to_jiffies(value));
-		set_baseline_state(trigger_data);	/* resets timer */
-	}
+	cancel_delayed_work_sync(&trigger_data->work);
+
+	atomic_set(&trigger_data->interval, msecs_to_jiffies(value));
+	set_baseline_state(trigger_data);	/* resets timer */
 
 	return size;
 }
-- 
2.56.0

Re: [PATCH v6 4/5] leds: trigger: netdev: Report invalid interval to user space

[sashiko-bot]

> From: Alexander Sverdlin <alexander.sverdlin@siemens.com>
> 
> interval_store() silently accepts out-of-range values: a write outside
> the [5, 10000] ms bounds returns the full count as if it succeeded, yet
> the interval is left unchanged.
> 
> Reject out-of-range values with -EINVAL instead.
> 
> Cc: stable@vger.kernel.org
> Fixes: 06f502f57d0d ("leds: trigger: Introduce a NETDEV trigger")
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261027113349.383147-1-alexander.sverdlin@siemens.com?part=4

[PATCH v6 5/5] 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(). interval_store() now tests
->hw_control under the lock too, so it can no longer sample a stale value
and change the interval while a concurrent store enables offload.

The async cancel cannot stop a worker already blocked on the lock: it may
resume after a store enabled hw_control and keep software-blinking and
rescheduling itself. Gate the worker and its arming in set_baseline_state()
on a shared netdev_trig_sw_blink() helper, so it stops once offload is
active or RX/TX monitoring is off.

set_baseline_state() can also re-arm the worker from a store that acquires
trigger_data->lock in the window between a notifier's
cancel_delayed_work_sync() and the notifier taking the same lock. The
notifier then sets carrier_link_up = false but does not cancel the re-armed
work. Gate netdev_trig_sw_blink() on carrier_link_up as well, so a worker
left armed across a link-down stops instead of blinking.

Cc: stable@vger.kernel.org
Closes: https://lore.kernel.org/all/sashiko-outbox-178980@kernel.org/
Fixes: d5e01266e7f5 ("leds: trigger: netdev: add additional specific link speed mode")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
---
Changelog:
v6:
- fixed unlocked hw_control check in interval_store()
- added missing carrier_link_up check in netdev_trig_sw_blink()
v4:
- introduced netdev_trig_sw_blink() and used it in netdev_trig_work()
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 | 56 +++++++++++++++++++--------
 1 file changed, 39 insertions(+), 17 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index b1f84014acab9..a503a4d64cefd 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -81,6 +81,17 @@ struct led_netdev_data {
 
 static const struct attribute_group netdev_trig_link_speed_attrs_group;
 
+/* True while the software activity worker should keep polling and blinking. */
+static bool netdev_trig_sw_blink(struct led_netdev_data *trigger_data)
+{
+	return trigger_data->net_dev && !trigger_data->hw_control &&
+	       trigger_data->carrier_link_up &&
+	       (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));
+}
+
 static void set_baseline_state(struct led_netdev_data *trigger_data)
 {
 	int current_brightness;
@@ -164,10 +175,7 @@ static void set_baseline_state(struct led_netdev_data *trigger_data)
 		/* If we are looking for RX/TX start periodically
 		 * checking stats
 		 */
-		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))
+		if (netdev_trig_sw_blink(trigger_data))
 			schedule_delayed_work(&trigger_data->work, 0);
 	}
 }
@@ -385,7 +393,7 @@ 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;
 
@@ -417,6 +425,10 @@ 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) &&
@@ -429,20 +441,26 @@ 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;
 }
 
@@ -494,9 +512,6 @@ static ssize_t interval_store(struct device *dev,
 	unsigned long value;
 	int ret;
 
-	if (trigger_data->hw_control)
-		return -EINVAL;
-
 	ret = kstrtoul(buf, 0, &value);
 	if (ret)
 		return ret;
@@ -505,11 +520,21 @@ static ssize_t interval_store(struct device *dev,
 	if (value < 5 || value > 10000)
 		return -EINVAL;
 
-	cancel_delayed_work_sync(&trigger_data->work);
+	/* async cancel: the worker takes this lock */
+	mutex_lock(&trigger_data->lock);
+
+	if (trigger_data->hw_control) {
+		mutex_unlock(&trigger_data->lock);
+		return -EINVAL;
+	}
+
+	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;
 }
 
@@ -691,11 +716,8 @@ static void netdev_trig_work(struct work_struct *work)
 		return;
 	}
 
-	/* If we are not looking for RX/TX then return  */
-	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)) {
+	/* Nothing to do under hw offload or without RX/TX monitoring */
+	if (!netdev_trig_sw_blink(trigger_data)) {
 		mutex_unlock(&trigger_data->lock);
 		return;
 	}
-- 
2.56.0

Re: [PATCH v6 5/5] leds: trigger: netdev: Serialize mode/interval stores with trigger lock

[sashiko-bot]

> 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
> [ ... ]
> 
> Cc: stable@vger.kernel.org
> Closes: https://lore.kernel.org/all/sashiko-outbox-178980@kernel.org/
> Fixes: d5e01266e7f5 ("leds: trigger: netdev: add additional specific link speed mode")
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261027113349.383147-1-alexander.sverdlin@siemens.com?part=5