linux-kernel - Re: [PATCH v2] thunderbolt: For dev authorization changes, include the actual event in udev change notification

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Date:   Fri, 30 Jul 2021 16:55:34 -0700
From:   Rajat Jain <rajatja@...gle.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <yehezkelshb@...il.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rajatxjain@...il.com
Subject: Re: [PATCH v2] thunderbolt: For dev authorization changes, include
 the actual event in udev change notification

On Mon, Jul 26, 2021 at 6:40 AM Mika Westerberg
<mika.westerberg@...ux.intel.com> wrote:
>
> Hi Rajat,
>
> On Fri, Jul 23, 2021 at 05:41:58PM -0700, Rajat Jain wrote:
> > (fixing the typo in the email ID for Greg).
> >
> > On Fri, Jul 23, 2021 at 5:40 PM Rajat Jain <rajatja@...gle.com> wrote:
> > >
> > > For security, we would like to monitor and track when the thunderbolt
> > > devices are authorized and deauthorized (i.e. when the thunderbolt sysfs
> > > "authorized" attribute changes). Currently the userspace gets a udev
> > > change notification when there is a change, but the state may have
> > > changed (again) by the time we look at the authorized attribute in
> > > sysfs. So an authorization event may go unnoticed. Thus make it easier
> > > by informing the actual change (new value of authorized attribute) in
> > > the udev change notification.
> > >
> > > The change is included as a key value "authorized=<val>" where <val>
> > > is the new value of sysfs attribute "authorized", and is described at
> > > Documentation/ABI/testing/sysfs-bus-thunderbolt under
> > > /sys/bus/thunderbolt/devices/.../authorized
>
> Looking good, a couple of minor nits below.
>
> > >
> > > Signed-off-by: Rajat Jain <rajatja@...gle.com>
> > > ---
> > >  drivers/thunderbolt/switch.c | 8 ++++++--
> > >  1 file changed, 6 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
> > > index 83b1ef3d5d03..382128dfbdee 100644
> > > --- a/drivers/thunderbolt/switch.c
> > > +++ b/drivers/thunderbolt/switch.c
> > > @@ -1499,6 +1499,7 @@ static ssize_t authorized_show(struct device *dev,
> > >  static int disapprove_switch(struct device *dev, void *not_used)
> > >  {
> > >         struct tb_switch *sw;
> > > +       char *envp[] = { "AUTHORIZED=0", NULL };
>
> Can you move arrange this to be before sw, like:

Done.

>
>         char *envp[] = { "AUTHORIZED=0", NULL };
>         struct tb_switch *sw;
>
> > >
> > >         sw = tb_to_switch(dev);
> > >         if (sw && sw->authorized) {
> > > @@ -1514,7 +1515,7 @@ static int disapprove_switch(struct device *dev, void *not_used)
> > >                         return ret;
> > >
> > >                 sw->authorized = 0;
> > > -               kobject_uevent(&sw->dev.kobj, KOBJ_CHANGE);
> > > +               kobject_uevent_env(&sw->dev.kobj, KOBJ_CHANGE, envp);
> > >         }
> > >
> > >         return 0;
> > > @@ -1523,6 +1524,8 @@ static int disapprove_switch(struct device *dev, void *not_used)
> > >  static int tb_switch_set_authorized(struct tb_switch *sw, unsigned int val)
> > >  {
> > >         int ret = -EINVAL;
> > > +       char envp_string[13];
> > > +       char *envp[] = { envp_string, NULL };
>
> Ditto.

Done. I still needed to define envp_string before envp (because it is
used in initialization).

I sent out a v3 with these changes.

Thanks,

Rajat

>
> > >
> > >         if (!mutex_trylock(&sw->tb->lock))
> > >                 return restart_syscall();
> > > @@ -1560,7 +1563,8 @@ static int tb_switch_set_authorized(struct tb_switch *sw, unsigned int val)
> > >         if (!ret) {
> > >                 sw->authorized = val;
> > >                 /* Notify status change to the userspace */
> > > -               kobject_uevent(&sw->dev.kobj, KOBJ_CHANGE);
> > > +               sprintf(envp_string, "AUTHORIZED=%u", sw->authorized);
> > > +               kobject_uevent_env(&sw->dev.kobj, KOBJ_CHANGE, envp);
> > >         }
> > >
> > >  unlock:
> > > --
> > > 2.32.0.432.gabb21c7263-goog
> > >