[PATCH v3] thunderbolt: For dev authorization changes, include the actual event in udev change notification

[PATCH v3] thunderbolt: For dev authorization changes, include the actual event in udev change notification

[Rajat Jain]

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

Signed-off-by: Rajat Jain <rajatja@google.com>
---
v3: rearrange the local variable definitions, add comments
v2: Commit log changes

 drivers/thunderbolt/switch.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 83b1ef3d5d03..dc2005bbd682 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -1498,6 +1498,7 @@ static ssize_t authorized_show(struct device *dev,
 
 static int disapprove_switch(struct device *dev, void *not_used)
 {
+	char *envp[] = { "AUTHORIZED=0", NULL };
 	struct tb_switch *sw;
 
 	sw = tb_to_switch(dev);
@@ -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;
@@ -1522,7 +1523,9 @@ static int disapprove_switch(struct device *dev, void *not_used)
 
 static int tb_switch_set_authorized(struct tb_switch *sw, unsigned int val)
 {
+	char envp_string[13];
 	int ret = -EINVAL;
+	char *envp[] = { envp_string, NULL };
 
 	if (!mutex_trylock(&sw->tb->lock))
 		return restart_syscall();
@@ -1559,8 +1562,12 @@ 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);
+		/*
+		 * Notify status change to the userspace, informing the new
+		 * value of /sys/bus/thunderbolt/devices/.../authorized
+		 */
+		sprintf(envp_string, "AUTHORIZED=%u", sw->authorized);
+		kobject_uevent_env(&sw->dev.kobj, KOBJ_CHANGE, envp);
 	}
 
 unlock:
-- 
2.32.0.554.ge1b32706d8-goog

Re: [PATCH v3] thunderbolt: For dev authorization changes, include the actual event in udev change notification

[Mika Westerberg]

Hi Rajat,

On Fri, Jul 30, 2021 at 04:53:04PM -0700, Rajat Jain 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
> 
> Signed-off-by: Rajat Jain <rajatja@google.com>

I did some tiny changes to the title, commit message and the comment and
applied to thunderbolt.git/next, thanks!

Re: [PATCH v3] thunderbolt: For dev authorization changes, include the actual event in udev change notification

[Rajat Jain]

On Mon, Aug 2, 2021 at 8:07 AM Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
>
> Hi Rajat,
>
> On Fri, Jul 30, 2021 at 04:53:04PM -0700, Rajat Jain 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
> >
> > Signed-off-by: Rajat Jain <rajatja@google.com>
>
> I did some tiny changes to the title, commit message and the comment and
> applied to thunderbolt.git/next, thanks!

Thank you!

Rajat