Merge tag 'configfs-for-5.2-2' of git://git.infradead.org/users/hch/configfs

Pull configs fix from Christoph Hellwig:

 - fix a use after free in configfs_d_iput (Sahitya Tummala)

* tag 'configfs-for-5.2-2' of git://git.infradead.org/users/hch/configfs:
  configfs: Fix use-after-free when accessing sd->s_dentry

1 files changed, 6 insertions, 8 deletions

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 5e7932d668ab..22203a3423a3 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -58,15 +58,13 @@ static void configfs_d_iput(struct dentry * dentry,
 	if (sd) {
 		/* Coordinate with configfs_readdir */
 		spin_lock(&configfs_dirent_lock);
-		/* Coordinate with configfs_attach_attr where will increase
-		 * sd->s_count and update sd->s_dentry to new allocated one.
-		 * Only set sd->dentry to null when this dentry is the only
-		 * sd owner.
-		 * If not do so, configfs_d_iput may run just after
-		 * configfs_attach_attr and set sd->s_dentry to null
-		 * even it's still in use.
+		/*
+		 * Set sd->s_dentry to null only when this dentry is the one
+		 * that is going to be killed.  Otherwise configfs_d_iput may
+		 * run just after configfs_attach_attr and set sd->s_dentry to
+		 * NULL even it's still in use.
 		 */
-		if (atomic_read(&sd->s_count) <= 2)
+		if (sd->s_dentry == dentry)
 			sd->s_dentry = NULL;
 
 		spin_unlock(&configfs_dirent_lock);