linux-kernel - Re: [PULL] Smack: Restore the smackfsdef mount option

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Message-ID: <327199b6-a7d3-8c07-fb14-2cc04b370a78@schaufler-ca.com>
Date:   Tue, 28 May 2019 13:37:06 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     David Howells <dhowells@...hat.com>
Cc:     James Morris <jmorris@...ei.org>,
        Linux Security Module list 
        <linux-security-module@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        LKML <linux-kernel@...r.kernel.org>, casey@...aufler-ca.com
Subject: Re: [PULL] Smack: Restore the smackfsdef mount option

On 5/28/2019 1:18 PM, David Howells wrote:
> Casey Schaufler <casey@...aufler-ca.com> 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