Re: [PATCH 00/12] acl: remove remaining posix acl handlers

[Christoph Hellwig <hch@lst.de>]

On Mon, Jan 30, 2023 at 10:10:52AM +0100, Christian Brauner wrote:
> However, a few filesystems still rely on the ->list() method of the
> generix POSIX ACL xattr handlers in their ->listxattr() inode operation.
> This is a very limited set of filesystems. For most of them there is no
> dependence on the generic POSIX ACL xattr handler in any way.
> 
> In addition, during inode initalization in inode_init_always() the
> registered xattr handlers in sb->s_xattr are used to raise IOP_XATTR in
> inode->i_opflags.
> 
> With the incoming removal of the legacy POSIX ACL handlers it is at
> least possible for a filesystem to only implement POSIX ACLs but no
> other xattrs. If that were to happen we would miss to raise IOP_XATTR
> because sb->s_xattr would be NULL. While there currently is no such
> filesystem we should still make sure that this just works should it ever
> happen in the future.

Now the real questions is: do we care?  Once Posix ACLs use an
entirely separate path, nothing should rely on IOP_XATTR for them.
So instead I think we're better off auditing all users of IOP_XATTR
and making sure that nothing relies on them for ACLs, as we've very
much split the VFS concept of ACLs from that from xattrs otherwise.