kobject: send KOBJ_REMOVE uevent when the object is removed from sysfs

It is possible for a KOBJ_REMOVE uevent to be sent to userspace way
after the files are actually gone from sysfs, due to how reference
counting for kobjects work.  This should not be a problem, but it would
be good to properly send the information when things are going away, not
at some later point in time in the future.

Before this move, if a kobject's parent was torn down before the child,
when the call to kobject_uevent() happened, the parent walk to try to
reconstruct the full path of the kobject could be a total mess and cause
crashes.  It's not good to try to tear down a kobject tree from top
down, but let's at least try to not to crash if a user does so.

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20200524153041.2361-2-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/lib/kobject.c b/lib/kobject.c
index 83198cb37d8d93b6ac5263b16b4a9c72e5a958ef..2509e22ad74a994cab6f27591120699c3de3e98d 100644 (file)
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -620,6 +620,13 @@ void kobject_del(struct kobject *kobj)
        if (ktype)
                sysfs_remove_groups(kobj, ktype->default_groups);
 
+       /* send "remove" if the caller did not do it but sent "add" */
+       if (kobj->state_add_uevent_sent && !kobj->state_remove_uevent_sent) {
+               pr_debug("kobject: '%s' (%p): auto cleanup 'remove' event\n",
+                        kobject_name(kobj), kobj);
+               kobject_uevent(kobj, KOBJ_REMOVE);
+       }
+
        sysfs_remove_dir(kobj);
        sysfs_put(sd);
 
@@ -673,13 +680,6 @@ static void kobject_cleanup(struct kobject *kobj)
                pr_debug("kobject: '%s' (%p): does not have a release() function, it is broken and must be fixed. See Documentation/kobject.txt.\n",
                         kobject_name(kobj), kobj);
 
-       /* send "remove" if the caller did not do it but sent "add" */
-       if (kobj->state_add_uevent_sent && !kobj->state_remove_uevent_sent) {
-               pr_debug("kobject: '%s' (%p): auto cleanup 'remove' event\n",
-                        kobject_name(kobj), kobj);
-               kobject_uevent(kobj, KOBJ_REMOVE);
-       }
-
        /* remove from sysfs if the caller did not do it */
        if (kobj->state_in_sysfs) {
                pr_debug("kobject: '%s' (%p): auto cleanup kobject_del\n",