1 files changed, 39 insertions, 28 deletions

diff --git a/kernel/user.c b/kernel/user.c
index 850e0ba..2c000e7 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -75,21 +75,6 @@ static void uid_hash_remove(struct user_struct *up)
 	put_user_ns(up->user_ns);
 }
 
-static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
-{
-	struct user_struct *user;
-	struct hlist_node *h;
-
-	hlist_for_each_entry(user, h, hashent, uidhash_node) {
-		if (user->uid == uid) {
-			atomic_inc(&user->__count);
-			return user;
-		}
-	}
-
-	return NULL;
-}
-
 #ifdef CONFIG_USER_SCHED
 
 static void sched_destroy_user(struct user_struct *up)
@@ -119,6 +104,23 @@ static int sched_create_user(struct user_struct *up) { return 0; }
 
 #if defined(CONFIG_USER_SCHED) && defined(CONFIG_SYSFS)
 
+static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
+{
+	struct user_struct *user;
+	struct hlist_node *h;
+
+	hlist_for_each_entry(user, h, hashent, uidhash_node) {
+		if (user->uid == uid) {
+			/* possibly resurrect an "almost deleted" object */
+			if (atomic_inc_return(&user->__count) == 1)
+				cancel_delayed_work(&user->work);
+			return user;
+		}
+	}
+
+	return NULL;
+}
+
 static struct kset *uids_kset; /* represents the /sys/kernel/uids/ directory */
 static DEFINE_MUTEX(uids_mutex);
 
@@ -283,12 +285,12 @@ int __init uids_sysfs_init(void)
 	return uids_user_create(&root_user);
 }
 
-/* work function to remove sysfs directory for a user and free up
+/* delayed work function to remove sysfs directory for a user and free up
  * corresponding structures.
  */
 static void cleanup_user_struct(struct work_struct *w)
 {
-	struct user_struct *up = container_of(w, struct user_struct, work);
+	struct user_struct *up = container_of(w, struct user_struct, work.work);
 	unsigned long flags;
 	int remove_user = 0;
 
@@ -297,15 +299,12 @@ static void cleanup_user_struct(struct work_struct *w)
 	 */
 	uids_mutex_lock();
 
-	local_irq_save(flags);
-
-	if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
+	spin_lock_irqsave(&uidhash_lock, flags);
+	if (atomic_read(&up->__count) == 0) {
 		uid_hash_remove(up);
 		remove_user = 1;
-		spin_unlock_irqrestore(&uidhash_lock, flags);
-	} else {
-		local_irq_restore(flags);
 	}
+	spin_unlock_irqrestore(&uidhash_lock, flags);
 
 	if (!remove_user)
 		goto done;
@@ -331,16 +330,28 @@ done:
  */
 static void free_user(struct user_struct *up, unsigned long flags)
 {
-	/* restore back the count */
-	atomic_inc(&up->__count);
 	spin_unlock_irqrestore(&uidhash_lock, flags);
-
-	INIT_WORK(&up->work, cleanup_user_struct);
-	schedule_work(&up->work);
+	INIT_DELAYED_WORK(&up->work, cleanup_user_struct);
+	schedule_delayed_work(&up->work, msecs_to_jiffies(1000));
 }
 
 #else	/* CONFIG_USER_SCHED && CONFIG_SYSFS */
 
+static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
+{
+	struct user_struct *user;
+	struct hlist_node *h;
+
+	hlist_for_each_entry(user, h, hashent, uidhash_node) {
+		if (user->uid == uid) {
+			atomic_inc(&user->__count);
+			return user;
+		}
+	}
+
+	return NULL;
+}
+
 int uids_sysfs_init(void) { return 0; }
 static inline int uids_user_create(struct user_struct *up) { return 0; }
 static inline void uids_mutex_lock(void) { }