linux-kernel - RE: [PATCH] Introduce support for Systems Management Driver over WMI for Dell Systems

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Message-ID: <DM6PR19MB2636225813D7359A210D8DCCFA2C0@DM6PR19MB2636.namprd19.prod.outlook.com>
Date:   Thu, 3 Sep 2020 14:27:10 +0000
From:   "Limonciello, Mario" <Mario.Limonciello@...l.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Hans de Goede <hdegoede@...hat.com>
CC:     Divya Bharathi <divya27392@...il.com>,
        Darren Hart <dvhart@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        "Bharathi, Divya" <Divya.Bharathi@...l.com>,
        "Ksr, Prasanth" <Prasanth.Ksr@...l.com>
Subject: RE: [PATCH] Introduce support for Systems Management Driver over WMI
 for Dell Systems

Andy,

Thanks for your feedback.
> 
> > > +bool get_pending_changes(void)
> > > +{
> > > +     struct wmi_interface_priv *priv;
> > > +
> > > +     priv = get_first_interface_priv();
> > > +     if (priv)
> > > +             return priv->pending_changes;
> 
> > > +     return 0;
> 
> 0 is not boolean.


Ack

> 
> > > +}
> 
> ...
> 
> > > +int set_attribute(const char *a_name, const char *a_value)
> > > +{
> 
> > > +     int ret = -1;
> > > +     int i;
> > > +     u8 *name_len, *value_len;
> > > +     char *current_password, *attribute_name, *attribute_value;
> > > +     size_t security_area_size;
> > > +     size_t string_area_size;
> > > +     size_t buffer_size;
> > > +     struct wmi_interface_priv *priv;
> > > +     char *buffer;
> 
> Consider to use reversed xmas tree order. And what -1 means?

Ack

> 
> > > +     /* look up if user set a password for the requests */
> > > +     current_password = get_current_password("Admin");
> > > +     if (!current_password)
> > > +             return -ENODEV;
> >
> > Can we instead of passing "Admin" and "System" to this function
> > just have 2 separate get_current_admin_password and
> get_current_system_password
> > helpers and then drop the error handling ?

The error handling for -ENODEV is actually important in case a WMI driver
was unbound.

> >
> > > +
> > > +     /* password is set */
> > > +     if (strlen(current_password) > 0)
> > > +             security_area_size = (sizeof(u32) * 2) +
> strlen(current_password) +
> > > +                                     strlen(current_password) % 2;
> > > +     /* password not set */
> > > +     else
> > > +             security_area_size = sizeof(u32) * 2;
> >
> > Since you are using more then 1 line here please use {} around the state-
> ments,
> > also please put the /* password not set */ after the else:
> >
> >                 ...
> >         } else { /* password not set */
> >                 ...
> >
> > > +     string_area_size = (strlen(a_name) + strlen(a_value))*2;
> > > +     buffer_size = security_area_size + string_area_size + sizeof(u16) *
> 2;
> > > +
> > > +     buffer = kzalloc(buffer_size, GFP_KERNEL);
> 
> Actually above looks like home grown kasprintf() implementation.

I don't think so, sprintf isn't used at all here.  It's a calculation to determine
the size of the buffer to use.

> 
> > > +     if (!buffer)
> > > +             return -ENOMEM;
> > > +
> > > +     /* build security area */
> > > +     if (strlen(current_password) > 0)
> > > +             populate_security_buffer(buffer, current_password);
> 
> > > +     name_len = buffer + security_area_size;
> > > +     attribute_name = name_len + sizeof(u16);
> > > +     value_len = attribute_name + strlen(a_name)*2;
> > > +     attribute_value = value_len + sizeof(u16);
> > > +
> > > +     /* turn into UTF16 strings, no NULL terminator */
> > > +     *name_len = strlen(a_name)*2;
> > > +     *value_len = strlen(a_value)*2;
> > > +     for (i = 0; i < strlen(a_name); i++)
> > > +             attribute_name[i*2] = a_name[i];
> > > +     for (i = 0; i < strlen(a_value); i++)
> > > +             attribute_value[i*2] = a_value[i];
> >
> > This assumes the incoming string is ASCII only and won't
> > work when the incoming string is UTF-8. It is probably
> > better to use the utf8s_to_utf16s() helper from the nls
> > code, this will mean adding a dependency on CONFIG_NLS
> > which typically is used for filesystem code, but I think
> > that that will be fine.
> 
> +1. Also my thought.

Ack

> 
> > > +     mutex_lock(&call_mutex);
> > > +     priv = get_first_interface_priv();
> > > +     if (!priv) {
> > > +             ret = -ENODEV;
> 
> > > +             pr_err(DRIVER_NAME ": no WMI backend bound");
> 
> If you wish, define pr_fmt() rather than putting this DRIVER_NAME to
> each of the pr_*() call.

Ack, we'll add pr_fmt.

> 
> > > +             goto out_set_attribute;
> > > +     }
> > > +
> > > +     ret = call_biosattributes_interface(priv->wdev, buffer, buffer_size,
> > > +                                             SETATTRIBUTE_METHOD_ID);
> > > +     if (ret == -EOPNOTSUPP)
> > > +             dev_err(&priv->wdev->dev, "admin password must be
> configured");
> > > +     else if (ret == -EACCES)
> > > +             dev_err(&priv->wdev->dev, "invalid password");
> > > +
> > > +     priv->pending_changes = 1;
> > > +out_set_attribute:
> > > +     kfree(buffer);
> > > +     mutex_unlock(&call_mutex);
> > > +
> > > +     return ret;
> > > +}
> 
> Above comments, as a rule of thumb, should be considered against
> entire code (where appropriate and applicable).

Thanks, the team will adjust against all the code for the next patch.