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

[Hans de Goede]

Hi,

On 2-Oct-24 2:08 PM, Rafael J. Wysocki wrote:
> 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?

AFAICT the patches don't really depend on each other, so my plan
was that you take patches 1-2 and I take patch 3 as a fix for
6.12-rc# .

Does that work for you ?

Regards,

Hans




> 
>> ---
>>  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
>>
>