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

[Mika Westerberg <mika.westerberg@linux.intel.com>]

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@google.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@google.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:

	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.

> >
> >         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
> >