From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 56348560d495d2501e87db559a61de717cd3ab02 upstream.

Some subsystems want to add debugfs files at early boot, way before
debugfs is initialized.  This seems to work somehow as the vfs layer
will not allow it to happen, but let's be explicit and test to ensure we
are properly up and running before allowing files to be created.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: stable <redacted>
Reported-by: Michael Walle <redacted>
Reported-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210218100818.3622317-2-gregkh@linuxfoundation.org (local)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/debugfs/inode.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c

@@ -315,6 +315,9 @@ static struct dentry *start_creating(con
 	struct dentry *dentry;
 	int error;
 
+	if (!debugfs_initialized())
+		return ERR_PTR(-ENOENT);
+
 	pr_debug("creating file '%s'\n", name);
 
 	if (IS_ERR(parent))