linux-kernel - Re: [PATCH v1 1/2] certs: Remove panic() calls from blacklist

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Date:   Sun, 20 Mar 2022 23:04:26 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Paul Moore <paul@...l-moore.com>
Cc:     Mickaël Salaün <mic@...ikod.net>,
        David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Snowberg <eric.snowberg@...cle.com>,
        Mickaël Salaün <mic@...ux.microsoft.com>,
        keyrings@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/2] certs: Remove panic() calls from blacklist_init()

On Fri, Mar 11, 2022 at 05:00:32PM -0500, Paul Moore wrote:
> On Fri, Mar 11, 2022 at 12:47 PM Mickaël Salaün <mic@...ikod.net> wrote:
> > From: Mickaël Salaün <mic@...ux.microsoft.com>
> >
> > Replace panic() calls from device_initcall(blacklist_init) with proper
> > error handling using -ENODEV.
> >
> > Suggested-by: Jarkko Sakkinen <jarkko@...nel.org> [1]
> > Link: https://lore.kernel.org/r/Yik0C2t7G272YZ73@iki.fi [1]
> > Signed-off-by: Mickaël Salaün <mic@...ux.microsoft.com>
> > Link: https://lore.kernel.org/r/20220311174741.250424-2-mic@digikod.net
> > ---
> >  certs/blacklist.c | 27 +++++++++++++++++++++------
> >  1 file changed, 21 insertions(+), 6 deletions(-)
> 
> I'm not sure we can safely rely on a non-zero error code saving us in
> the care of failure, can we?
> 
> The blacklist_init() function is registered as an initcall via
> device_initcall() which I believe is either executed via
> do_init_module() in the case of a dynamic module load, or via
> do_initcalls() if built into the kernel.  In either case the result is
> that the module/functionality doesn't load and the kernel continues on
> executing.  While this could be acceptable for some non-critical
> modules, if this particular module fails to load it defeats the
> certificate/key based deny list for signed modules, yes?
> 
> I completely understand the strong desire to purge the kernel of
> panic()s, BUG()s, and the like, but if a critical piece of security
> functionality that users expect to be present fails to initialize,
> panic()ing is likely the right thing to do.

OK, I get this. 

What this function should have is this information documented in
the header. Otherwise, this is just confusing.

BR, Jarkko