Re: [PATCH] sh: hp6xx: unset apm_get_power_status on unload

On 2026-04-12 09:30, John Paul Adrian Glaubitz wrote:
> Hi Ahelenia,
> 
> On Fri, 2025-10-17 at 00:05 +0200, Ahelenia Ziemiańska wrote:
>> The API for apm_get_power_status is "call it if it isn't NULL".
>> If the module is unloaded and it's not unset,
>> reading /proc/apm will jump into unloaded kernel memory.
>> 
>> The first commit that added this incompletely refactored
>> the assigned-to variable in __exit,
>> the second deleted it instead of fixing it.
>> 
>> Unset it on unload like drivers/macintosh/apm_emu.c.
>> 
>> Fixes: 0a9b0db19262 ("[APM] SH: Convert to use shared APM emulation.")
>> Fixes: 8c8ee8254767 ("sh: hp6xx: APM build fix and new battery 
>> values.")
>> Signed-off-by: Ahelenia Ziemiańska <[email protected]>
>> ---
>>  arch/sh/boards/mach-hp6xx/hp6xx_apm.c | 3 +++
>>  1 file changed, 3 insertions(+)
>> 
>> diff --git a/arch/sh/boards/mach-hp6xx/hp6xx_apm.c 
>> b/arch/sh/boards/mach-hp6xx/hp6xx_apm.c
>> index e5c4c7d34139..089eca39c4e6 100644
>> --- a/arch/sh/boards/mach-hp6xx/hp6xx_apm.c
>> +++ b/arch/sh/boards/mach-hp6xx/hp6xx_apm.c
>> @@ -98,6 +98,9 @@ static int __init hp6x0_apm_init(void)
>> 
>>  static void __exit hp6x0_apm_exit(void)
>>  {
>> +	if (apm_get_power_status == hp6x0_apm_get_power_status)
>> +		apm_get_power_status = NULL;
>> +
>>  	free_irq(HP680_BTN_IRQ, 0);
>>  }
>> 
> 
> Let's CC Artur Rojek who has worked on the hp6xx code before and should 
> give his ACK.

This driver can't be built as a module, so this code is never called.
But since we can't get rid of module_exit(apm_exit):

Acked-by: Artur Rojek <[email protected]>

Cheers,
Artur

> 
> Adrian