Hi,
On 2/19/21 12:26 AM, Limonciello, Mario wrote:
>
>
>> -----Original Message-----
>> From: mark gross <mgross@xxxxxxxxxxxxxxx>
>> Sent: Thursday, February 18, 2021 16:49
>> To: Limonciello, Mario
>> Cc: Hans De Goede; Mark Gross; LKML; platform-driver-x86@xxxxxxxxxxxxxxx;
>> Bharathi, Divya; Alexander Naumann
>> Subject: Re: [PATCH] platform/x86: dell-wmi-sysman: correct an initialization
>> failure
>>
>>
>> [EXTERNAL EMAIL]
>>
>> On Thu, Feb 18, 2021 at 01:17:23PM -0600, Mario Limonciello wrote:
>>> On Dell systems that don't support this interface the module is
>>> mistakingly returning error code "0", when it should be returning
>>> -ENODEV. Correct a logic error to guarantee the correct return code.
>>>
>>> Cc: Divya Bharathi <Divya_Bharathi@xxxxxxxx>
>>> Reported-by: Alexander Naumann <alexandernaumann@xxxxxx>
>>> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxxx>
>>> ---
>>> drivers/platform/x86/dell-wmi-sysman/biosattr-interface.c | 4 +++-
>>> drivers/platform/x86/dell-wmi-sysman/passwordattr-interface.c | 4 +++-
>>> drivers/platform/x86/dell-wmi-sysman/sysman.c | 4 ++--
>>> 3 files changed, 8 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/platform/x86/dell-wmi-sysman/biosattr-interface.c
>> b/drivers/platform/x86/dell-wmi-sysman/biosattr-interface.c
>>> index f95d8ddace5a..8d59f81f9db4 100644
>>> --- a/drivers/platform/x86/dell-wmi-sysman/biosattr-interface.c
>>> +++ b/drivers/platform/x86/dell-wmi-sysman/biosattr-interface.c
>>> @@ -175,7 +175,9 @@ static struct wmi_driver bios_attr_set_interface_driver
>> = {
>>>
>>> int init_bios_attr_set_interface(void)
>>> {
>>> - return wmi_driver_register(&bios_attr_set_interface_driver);
>>> + int ret = wmi_driver_register(&bios_attr_set_interface_driver);
>> I have to ask if the propper fix should be in wmi_driver_register
>
> Do you mean something like this?
>
> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
> index c669676ea8e8..89d04c5e3ab9 100644
> --- a/drivers/platform/x86/wmi.c
> +++ b/drivers/platform/x86/wmi.c
> @@ -1415,6 +1415,11 @@ static int acpi_wmi_probe(struct platform_device *device)
> int __must_check __wmi_driver_register(struct wmi_driver *driver,
> struct module *owner)
> {
> + const struct wmi_device_id *id = driver->id_table;
> +
> + if (!wmi_has_guid(id->guid_string))
> + return -ENODEV;
> +
> driver->driver.owner = owner;
> driver->driver.bus = &wmi_bus_type;
>
No, drivers should be able to register before the GUID shows up. I know that
the GUID showing up later will likely never happen with WMI, but having a match
check like this in the driver_register function is highly unusual and would
be different from what all other busses do.
But your initial fix here is wrong too, because it does call wmi_driver_register,
which succeeds and then makes sysman_init() exit with -ENODEV.
Returning -ENODEV from sysman_init() is what we want, this causes the entire
insmod to be aborted, without logging an error (because of -ENODEV) so the
code will not be taking up memory.
This means that the memory into which the module was loaded before the kernel
calls sysman_init() will be free-ed and now the *still* registered WMI driver
entry will point to that free-ed memory, which is not good (TM).
So instead init_bios_attr_set_interface() should become something like this:
int init_bios_attr_set_interface(void)
{
int ret;
ret = wmi_driver_register(&bios_attr_set_interface_driver);
if (ret)
return ret;
if (!wmi_priv.bios_attr_wdev) {
wmi_driver_unregister(&bios_attr_set_interface_driver);
return -ENODEV;
}
return 0;
}
And the same for the init_bios_attr_pass_interface() function.
This follows the standard kernel pattern that a function should always
undo any things / resource-allocations it has done on error before
exiting with an error.
Regards,
Hans
