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

[Armin Wolf]

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@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