Re: [PATCH v4 4/4] leds: trigger: netdev: Serialize mode/interval stores with trigger lock

[sashiko-bot@kernel.org]

> 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().
> 
> 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.
> 
> 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>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261001131206.2513248-1-alexander.sverdlin@siemens.com?part=4