Merge tag 'driver-core-6.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core fixes from Greg KH:
 "Here are two small driver core fixes for 6.1-rc6:

   - utsname fix, this one should already be in your tree as it came
     from a different tree earlier.

   - kernfs bugfix for a much reported syzbot report that seems to keep
     getting triggered.

  Both of these have been in linux-next for a while with no reported
  issues"

* tag 'driver-core-6.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  kernfs: Fix spurious lockdep warning in kernfs_find_and_get_node_by_id()
  kernel/utsname_sysctl.c: Add missing enum uts_proc value

1 files changed, 12 insertions, 2 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 3990f3e270cb..f33b3baad07c 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -31,10 +31,15 @@ static DEFINE_SPINLOCK(kernfs_idr_lock);	/* root->ino_idr */
 
 #define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
 
+static bool __kernfs_active(struct kernfs_node *kn)
+{
+	return atomic_read(&kn->active) >= 0;
+}
+
 static bool kernfs_active(struct kernfs_node *kn)
 {
 	lockdep_assert_held(&kernfs_root(kn)->kernfs_rwsem);
-	return atomic_read(&kn->active) >= 0;
+	return __kernfs_active(kn);
 }
 
 static bool kernfs_lockdep(struct kernfs_node *kn)
@@ -705,7 +710,12 @@ struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root,
 			goto err_unlock;
 	}
 
-	if (unlikely(!kernfs_active(kn) || !atomic_inc_not_zero(&kn->count)))
+	/*
+	 * We should fail if @kn has never been activated and guarantee success
+	 * if the caller knows that @kn is active. Both can be achieved by
+	 * __kernfs_active() which tests @kn->active without kernfs_rwsem.
+	 */
+	if (unlikely(!__kernfs_active(kn) || !atomic_inc_not_zero(&kn->count)))
 		goto err_unlock;
 
 	spin_unlock(&kernfs_idr_lock);