On Sun, Sep 22, 2024 at 8:40 AM Armin Wolf <W_Armin@xxxxxx> wrote:
>
> When a battery hook returns an error when adding a new battery, then
> the battery hook is automatically unregistered.
> However the battery hook provider cannot know that, so it will later
> call battery_hook_unregister() on the already unregistered battery
> hook, resulting in a crash.
>
> Fix this by using a boolean flag to mark already unregistered battery
> hooks as "dead" so that they can be ignored by
> battery_hook_unregister().
>
> Fixes: fa93854f7a7e ("battery: Add the battery hooking API")
> Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
> ---
> drivers/acpi/battery.c | 11 ++++++++++-
> include/acpi/battery.h | 1 +
> 2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
> index 10e9136897a7..b31a6183a082 100644
> --- a/drivers/acpi/battery.c
> +++ b/drivers/acpi/battery.c
> @@ -719,6 +719,7 @@ static void battery_hook_unregister_unlocked(struct acpi_battery_hook *hook)
> power_supply_changed(battery->bat);
> }
> list_del(&hook->list);
> + hook->dead = true;
It looks like you could do
list_del_init((&hook->list);
here and then do a list_emtpy() check below.
>
> pr_info("extension unregistered: %s\n", hook->name);
> }
> @@ -726,7 +727,14 @@ static void battery_hook_unregister_unlocked(struct acpi_battery_hook *hook)
> void battery_hook_unregister(struct acpi_battery_hook *hook)
> {
> mutex_lock(&hook_mutex);
> - battery_hook_unregister_unlocked(hook);
> + /*
> + * Ignore already unregistered battery hooks. This might happen
> + * if a battery hook was previously unloaded due to an error when
> + * adding a new battery.
> + */
> + if (!hook->dead)
if (!list_empty(&hook->list))
> + battery_hook_unregister_unlocked(hook);
> +
> mutex_unlock(&hook_mutex);
and the new struct field would not be necessary if I'm not mistaken.
> }
> EXPORT_SYMBOL_GPL(battery_hook_unregister);
> @@ -737,6 +745,7 @@ void battery_hook_register(struct acpi_battery_hook *hook)
>
> mutex_lock(&hook_mutex);
> INIT_LIST_HEAD(&hook->list);
Also the above statement is redundant, so maybe drop it while you're at it?
> + hook->dead = false;
> list_add(&hook->list, &battery_hook_list);
> /*
> * Now that the driver is registered, we need
> diff --git a/include/acpi/battery.h b/include/acpi/battery.h
> index c93f16dfb944..5cfe132bb7f5 100644
> --- a/include/acpi/battery.h
> +++ b/include/acpi/battery.h
> @@ -16,6 +16,7 @@ struct acpi_battery_hook {
> int (*add_battery)(struct power_supply *battery, struct acpi_battery_hook *hook);
> int (*remove_battery)(struct power_supply *battery, struct acpi_battery_hook *hook);
> struct list_head list;
> + bool dead;
> };
>
> void battery_hook_register(struct acpi_battery_hook *hook);
> --
