Re: [RFC PATCH v8 13/17] fsverity: consume builtin signature via LSM hook

From: Fan Wu <wufan(a)linux.microsoft.com&gt; fsverity represents a mechanism to support both integrity and authenticity protection of a file, supporting both signed and unsigned digests. An LSM which controls access to a resource based on authenticity and integrity of said resource, can then use this data to make an informed decision on the authorization (provided by the LSM's policy) of said claim. This effectively allows the extension of a policy enforcement layer in LSM for fsverity, allowing for more granular control of how a particular authenticity claim can be used. For example, "all (built-in) signed fsverity files should be allowed to execute, but only these hashes are allowed to be loaded as kernel modules". This enforcement must be done in kernel space, as a userspace only solution would fail a simple litmus test: Download a self-contained malicious binary that never touches the userspace stack. This binary would still be able to execute. Signed-off-by: Fan Wu <wufan(a)linux.microsoft.com&gt; Signed-off-by: Deven Bowers <deven.desai(a)linux.microsoft.com&gt;