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

From: Casey Schaufler
Date: Tue May 28 2019 - 16:40:38 EST

On 5/28/2019 1:18 PM, David Howells wrote:
> 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
> sb_eat_lsm_opts).
>>> 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.

I will test a fix if you point me to it. I need it for 5.1 and 5.2.

> David