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

1 files changed, 8 insertions, 6 deletions

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 9d20d5dd298a..4bbd38ec3788 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -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);
         }