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Date:   Fri, 8 May 2020 08:47:19 -0400
From:   Rafael Aquini <aquini@redhat.com>
To:     Luis Chamberlain <mcgrof@kernel.org>
Cc:     Tso Ted <tytso@mit.edu>, Adrian Bunk <bunk@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Laura Abbott <labbott@redhat.com>,
        Jeff Mahoney <jeffm@suse.com>, Jiri Kosina <jikos@kernel.org>,
        Jessica Yu <jeyu@suse.de>, Takashi Iwai <tiwai@suse.de>,
        Ann Davis <AnDavis@suse.com>,
        Richard Palethorpe <rpalethorpe@suse.de>,
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        keescook@chromium.org, akpm@linux-foundation.org, cai@lca.pw,
        rdunlap@infradead.org
Subject: Re: [PATCH v2] kernel: add panic_on_taint
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On Thu, May 07, 2020 at 10:25:58PM +0000, Luis Chamberlain wrote:
> On Thu, May 07, 2020 at 06:06:06PM -0400, Rafael Aquini wrote:
> > On Thu, May 07, 2020 at 08:33:40PM +0000, Luis Chamberlain wrote:
> > > I *think* that a cmdline route to enable this would likely remove the
> > > need for the kernel config for this. But even with Vlastimil's work
> > > merged, I think we'd want yet-another value to enable / disable this
> > > feature. Do we need yet-another-taint flag to tell us that this feature
> > > was enabled?
> > >
> > 
> > I guess it makes sense to get rid of the sysctl interface for
> > proc_on_taint, and only keep it as a cmdline option. 
> 
> That would be easier to support and k3eps this simple.
> 
> > But the real issue seems to be, regardless we go with a cmdline-only option
> > or not, the ability of proc_taint() to set any arbitrary taint flag 
> > other than just marking the kernel with TAINT_USER. 
> 
> I think we would have no other option but to add a new TAINT flag so
> that we know that the taint flag was modified by a user. Perhaps just
> re-using TAINT_USER when proc_taint() would suffice.
>

We might not need an extra taint flag if, perhaps, we could make these
two features mutually exclusive. The idea here is that bitmasks added 
via panic_on_taint get filtered out in proc_taint(), so a malicious 
user couldn't exploit the latter interface to easily panic the system,
when the first one is also in use. 
 
-- Rafael