It would probably make the exploit harder (unless the exploit targets the filesystem code itself), but there are almost always subtle gaps between "breaking the exploit" and "fixing the vulnerability". This is a fun question to dig into, though.
This is also very similar to the tactic of using an encrypted message digest in place of a MAC. The whole point of a MAC is that it can't be calculated without the secret that provides its security, and so schemes that use digests instead are (a) harder to attack than systems that do nothing and (b) still broken.
This is also very similar to the tactic of using an encrypted message digest in place of a MAC. The whole point of a MAC is that it can't be calculated without the secret that provides its security, and so schemes that use digests instead are (a) harder to attack than systems that do nothing and (b) still broken.