fs: add kern_path_locked_negative()

The audit code relies on the fact that kern_path_locked() returned a
negative dentry. Add a helper that implements these semantics to fix the
immediate bleeding. We can find a unified solution for this afterwards.

Fixes: 1c3cb50b58c3 ("VFS: change kern_path_locked() and user_path_locked_at() to never return negative dentry")
Signed-off-by: Christian Brauner <brauner@kernel.org>
3 files changed