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Commit 19ca2c8f authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 

Pull namespace fix from Eric Biederman:
 "This has a single brown bag fix.

  The possible deadlock with dec_pid_namespaces that I had thought was
  fixed earlier turned out only to have been moved. So instead of being
  cleaver this change takes ucounts_lock with irqs disabled. So
  dec_ucount can be used from any context without fear of deadlock.

  The items accounted for dec_ucount and inc_ucount are all
  comparatively heavy weight objects so I don't exepct this will have
  any measurable performance impact"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  userns: Make ucounts lock irq-safe
parents a4685d2f 880a3854

kernel/ucount.c

+8 −6
Original line number Diff line number Diff line
@@ -128,10 +128,10 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) 
	struct hlist_head *hashent = ucounts_hashentry(ns, uid);

	struct ucounts *ucounts, *new;



	spin_lock(&ucounts_lock);

	spin_lock_irq(&ucounts_lock);

	ucounts = find_ucounts(ns, uid, hashent);

	if (!ucounts) {

		spin_unlock(&ucounts_lock);

		spin_unlock_irq(&ucounts_lock);



		new = kzalloc(sizeof(*new), GFP_KERNEL);

		if (!new)
@@ -141,7 +141,7 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) 
		new->uid = uid;

		atomic_set(&new->count, 0);



		spin_lock(&ucounts_lock);

		spin_lock_irq(&ucounts_lock);

		ucounts = find_ucounts(ns, uid, hashent);

		if (ucounts) {

			kfree(new);
@@ -152,16 +152,18 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) 
	}

	if (!atomic_add_unless(&ucounts->count, 1, INT_MAX))

		ucounts = NULL;

	spin_unlock(&ucounts_lock);

	spin_unlock_irq(&ucounts_lock);

	return ucounts;

}



static void put_ucounts(struct ucounts *ucounts)

{

	unsigned long flags;



	if (atomic_dec_and_test(&ucounts->count)) {

		spin_lock(&ucounts_lock);

		spin_lock_irqsave(&ucounts_lock, flags);

		hlist_del_init(&ucounts->node);

		spin_unlock(&ucounts_lock);

		spin_unlock_irqrestore(&ucounts_lock, flags);



		kfree(ucounts);

	}