[PATCH V3] fs: generalize anon_inode_make_secure_inode() and fix secretmem LSM bypass

[Ira Weiny]

Shivank Garg wrote:
> Extend anon_inode_make_secure_inode() to take superblock parameter and
> make it available via fs.h. This allows other subsystems to create
> anonymous inodes with proper security context.
> 
> Use this function in secretmem to fix a security regression, where
> S_PRIVATE flag wasn't cleared after alloc_anon_inode(), causing
> LSM/SELinux checks to be skipped.
> 
> Using anon_inode_make_secure_inode() ensures proper security context
> initialization through security_inode_init_security_anon().
> 
> Fixes: 2bfe15c52612 ("mm: create security context for memfd_secret inodes")
> Suggested-by: David Hildenbrand <david at redhat.com>
> Suggested-by: Mike Rapoport (Microsoft) <rppt at kernel.org>
> Reviewed-by: David Hildenbrand <david at redhat.com>

Reviewed-by: Ira Weiny <ira.weiny at intel.com>

[snip]