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

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Date:   Tue, 28 May 2019 19:54:18 +0100
From:   David Howells <dhowells@...hat.com>
To:     Casey Schaufler <casey@...aufler-ca.com>
Cc:     dhowells@...hat.com, LKML <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>, jose.bollo@....bzh,
        Linux Security Module list 
        <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH] Smack: Restore the smackfsdef mount option

Casey Schaufler <casey@...aufler-ca.com> wrote:

> > Casey Schaufler <casey@...aufler-ca.com> wrote:
> >
> >>> Also, should all of these be prefixed with "smack"?  So:
> >>>
> >>>   	fsparam_string("smackfsdef",	Opt_fsdefault),
> >>>   	fsparam_string("smackfsfloor",	Opt_fsfloor),
> >>>   	fsparam_string("smackfshat",	Opt_fshat),	
> >> No. smack_fs_parameters takes care of that.
> > It does?  *Blink*.
> 
> Well, something does. I can't say that I 100% understand all
> of how the new mount code handles the mount options. Y'all made
> sweeping changes, and the code works the way it used to except
> for the awkward change from smackfsdef to smackfsdefault. It
> took no small amount of head scratching and experimentation to
> convince myself that the fix I proposed was correct.

Ah...  I suspect the issue is that smack_sb_eat_lsm_opts() strips the prefix
for an unconverted filesystem, but smack_fs_context_parse_param() doesn't
(which it shouldn't).

Can you try grabbing my mount-api-viro branch from:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git

and testing setting smack options on a tmpfs filesystem?

You might need to try modifying samples/vfs/test-fsmount.c to make it mount a
trmpfs filesystem through the new mount UAPI.

David