Re: [PATCH v6 9/9] modpost: Handle malformed WMI GUID strings

[Armin Wolf <W_Armin@gmx.de>]

Am 10.06.26 um 23:05 schrieb Pali Rohár:

> On Wednesday 10 June 2026 22:34:53 Armin Wolf wrote:
>> Some WMI GUIDs found inside binary MOF files contain both
>> uppercase and lowercase characters. Blindly copying such
>> GUIDs will prevent the associated WMI driver from loading
>> automatically because the WMI GUID found inside WMI device ids
>> always contains uppercase characters.
>>
>> Avoid this issue by always converting WMI GUID strings to
>> uppercase. Also verify that the WMI GUID string actually looks
>> like a valid GUID.
> Hello! Maybe different idea: Would not it be better to check in
> do_wmi_entry() if all letters are really upper case?
>
> Mixing lowercase and uppercase is a mess. And if somebody blindly copy
> lowercase from MOF files to some kernel wmi driver, we can check for
> this mistake in file2alias.c and throw an error.

guid_parse() handles mixed-case GUIDs just fine, so i prefer to accept them as well.

In the long term i am trying to move the whole WMI subsystem to guid_t or even class names
from the BMOF data.

Thanks,
Armin Wolf

>> Signed-off-by: Armin Wolf <W_Armin@gmx.de>
>> ---
>>   .../wmi/driver-development-guide.rst          |  2 +-
>>   scripts/mod/file2alias.c                      | 28 ++++++++++++++++++-
>>   2 files changed, 28 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/wmi/driver-development-guide.rst b/Documentation/wmi/driver-development-guide.rst
>> index 387f508d57ad..6290c448f5e7 100644
>> --- a/Documentation/wmi/driver-development-guide.rst
>> +++ b/Documentation/wmi/driver-development-guide.rst
>> @@ -54,7 +54,7 @@ to matching WMI devices using a struct wmi_device_id table:
>>   ::
>>   
>>     static const struct wmi_device_id foo_id_table[] = {
>> -         /* Only use uppercase letters! */
>> +         /* Using only uppercase letters is recommended */
>>            { "936DA01F-9ABD-4D9D-80C7-02AF85C822A8", NULL },
>>            { }
>>     };
>> diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
>> index 4e99393a35f1..20e542a888c4 100644
>> --- a/scripts/mod/file2alias.c
>> +++ b/scripts/mod/file2alias.c
>> @@ -1253,6 +1253,8 @@ static void do_tee_entry(struct module *mod, void *symval)
>>   static void do_wmi_entry(struct module *mod, void *symval)
>>   {
>>   	DEF_FIELD_ADDR(symval, wmi_device_id, guid_string);
>> +	char result[sizeof(*guid_string)];
>> +	int i;
>>   
>>   	if (strlen(*guid_string) != UUID_STRING_LEN) {
>>   		warn("Invalid WMI device id 'wmi:%s' in '%s'\n",
>> @@ -1260,7 +1262,31 @@ static void do_wmi_entry(struct module *mod, void *symval)
>>   		return;
>>   	}
>>   
>> -	module_alias_printf(mod, false, WMI_MODULE_PREFIX "%s", *guid_string);
>> +	for (i = 0; i < UUID_STRING_LEN; i++) {
>> +		char value = (*guid_string)[i];
>> +		bool valid = false;
>> +
>> +		if (i == 8 || i == 13 || i == 18 || i == 23) {
>> +			if (value == '-')
>> +				valid = true;
>> +		} else {
>> +			if (isxdigit(value))
>> +				valid = true;
>> +		}
>> +
>> +		if (!valid) {
>> +			warn("Invalid character %c inside WMI GUID string '%s' in '%s'\n",
>> +			     value, *guid_string, mod->name);
>> +			return;
>> +		}
>> +
>> +		/* Some GUIDs from BMOF definitions contain lowercase characters */
>> +		result[i] = toupper(value);
>> +	}
>> +
>> +	result[i] = '\0';
>> +
>> +	module_alias_printf(mod, false, WMI_MODULE_PREFIX "%s", result);
>>   }
>>   
>>   /* Looks like: mhi:S */
>> -- 
>> 2.39.5
>>