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

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 [off-list ref] wrote:

quoted

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.

quoted

Signed-off-by: Rajat Jain <redacted>
---
 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;

quoted

        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.

quoted

        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