Re: [PATCH] platform/x86: dell-smbios-wmi: Fix oops on rmmod dell_smbios

[mark gross <mgross@linux.intel.com>]

On Tue, May 18, 2021 at 02:50:27PM +0200, Hans de Goede wrote:
> init_dell_smbios_wmi() only registers the dell_smbios_wmi_driver on systems
> where the Dell WMI interface is support. While exit_dell_smbios_wmi()
> unregisters it unconditionally, this leads to the following oops:
> 
> [  175.722921] ------------[ cut here ]------------
> [  175.722925] Unexpected driver unregister!
> [  175.722939] WARNING: CPU: 1 PID: 3630 at drivers/base/driver.c:194 driver_unregister+0x38/0x40
> ...
> [  175.723089] Call Trace:
> [  175.723094]  cleanup_module+0x5/0xedd [dell_smbios]
> ...
> [  175.723148] ---[ end trace 064c34e1ad49509d ]---
> 
> Make the unregister happen on the same condition the register happens
> to fix this.
> 
> Cc: Mario Limonciello <mario.limonciello@outlook.com>
> Fixes: 1a258e670434 ("platform/x86: dell-smbios-wmi: Add new WMI dispatcher driver")
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  drivers/platform/x86/dell/dell-smbios-wmi.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/dell/dell-smbios-wmi.c b/drivers/platform/x86/dell/dell-smbios-wmi.c
> index a1753485159c..33f823772733 100644
> --- a/drivers/platform/x86/dell/dell-smbios-wmi.c
> +++ b/drivers/platform/x86/dell/dell-smbios-wmi.c
> @@ -270,7 +270,8 @@ int init_dell_smbios_wmi(void)
>  
>  void exit_dell_smbios_wmi(void)
>  {
> -	wmi_driver_unregister(&dell_smbios_wmi_driver);
> +	if (wmi_supported)
Something is fishy with this.  wmi_supported is used in the
init_dell_smbios_wmi function so we shouldn't even be able to call this
function if wmi_supported == 0

is there a bug in the wmi framework where drivers that fail to init are not
removed from a list resulting in a failure to unregister?  Is your fix hiding a
higher level issue?

Looking more shouldn't the prob function NOT get called if the init function
fails?


--mark

> +		wmi_driver_unregister(&dell_smbios_wmi_driver);
>  }
>  
>  MODULE_DEVICE_TABLE(wmi, dell_smbios_wmi_id_table);
> -- 
> 2.31.1
>