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

[Mario Limonciello <mario.limonciello@amd.com>]

On 3/7/2026 6:25 PM, 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.
> 
> 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 fbc2d9b12fe9..74bb156ad9cc 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);
> +	}

Minor logic change that could drop the boolean variable in the for loop:

for (i = 0; i < UUID_STRING_LEN; i++) {
	char value = (*guid_string)[i];

	if (isxdigit(value)) {
		result[i] = toupper(value);
		continue;
	}

	if (value == '-' && (i == 8 || i == 13 || i == 18 || i == 23)) {
		result[i] = value;
		continue;
	}

	warn("Invalid character %c inside WMI GUID string '%s' in '%s'\n",
	     value, *guid_string, mod->name);
	return;
}

> +
> +	result[i] = '\0';
> +
> +	module_alias_printf(mod, false, WMI_MODULE_PREFIX "%s", result);
>   }
>   
>   /* Looks like: mhi:S */