Re: [PATCH RESEND v3 2/3] ACPI: battery: Fix possible crash when unregistering a battery hook

[Rafael J. Wysocki]

On Tue, Oct 1, 2024 at 11:28 PM 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 the list head to mark already unregistered battery
> hooks as already being unregistered 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>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

Hans, are you going to take this series or should I apply it?

> ---
>  drivers/acpi/battery.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
> index dda59ee5a11e..1c45ff6dbb83 100644
> --- a/drivers/acpi/battery.c
> +++ b/drivers/acpi/battery.c
> @@ -715,7 +715,7 @@ static void battery_hook_unregister_unlocked(struct acpi_battery_hook *hook)
>                 if (!hook->remove_battery(battery->bat, hook))
>                         power_supply_changed(battery->bat);
>         }
> -       list_del(&hook->list);
> +       list_del_init(&hook->list);
>
>         pr_info("extension unregistered: %s\n", hook->name);
>  }
> @@ -723,7 +723,14 @@ 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 (!list_empty(&hook->list))
> +               battery_hook_unregister_unlocked(hook);
> +
>         mutex_unlock(&hook_mutex);
>  }
>  EXPORT_SYMBOL_GPL(battery_hook_unregister);
> @@ -733,7 +740,6 @@ void battery_hook_register(struct acpi_battery_hook *hook)
>         struct acpi_battery *battery;
>
>         mutex_lock(&hook_mutex);
> -       INIT_LIST_HEAD(&hook->list);
>         list_add(&hook->list, &battery_hook_list);
>         /*
>          * Now that the driver is registered, we need
> --
> 2.39.5
>