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

[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.

> Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
> ---
>  .../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
>