Re: [PULL] Smack: Restore the smackfsdef mount option

From: David Howells
Date: Tue May 28 2019 - 16:22:18 EST

Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote:

> > static const struct fs_parameter_spec smack_param_specs[] = {
> > + fsparam_string("fsdef", Opt_fsdefault),
> > fsparam_string("fsdefault", Opt_fsdefault),
> > fsparam_string("fsfloor", Opt_fsfloor),
> > fsparam_string("fshat", Opt_fshat),
> >
> > but that all the option names in that table *do* need prefixing with
> > "smack".

Actually, you're right, we do need to add that *and* prefix it with "smack".

> I'm not sure I follow the logic, because "mount -o smackfsdefault=Pop"
> does what I would expect it to.

Yes, I'm sure it does - for the cases you're testing - but it's filesystem and
syscall dependent. None of the filesystems currently ported to the mount API
upstream override ->parse_monolithic(), but that changes with nfs, shmem and
coda and will change with cifs too.

It also changes if you use fsconfig() to supply the options because that goes
through a different LSM hook (it uses fs_context_parse_param rather than

> > The way you enter the LSM is going to depend on whether
> > generic_parse_monolithic() is called. You're only going to enter this way
> > if mount(2) is the syscall of entry and the filesystem doesn't override
> > the ->parse_monolithic() option (none in the upstream kernel).
> So you're saying that the code works for the mount(2) case,
> but won't work for some other case? Are you planning a fix?
> Will that fix include restoration of smackfsdef?

I can do a fix, but testing it is a pain.