linux-kernel - Re: [PATCH] lockdown: ratelimit denial messages

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Date:   Wed, 14 Sep 2022 07:43:13 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Nathan Lynch <nathanl@...ux.ibm.com>
Cc:     linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, jmorris@...ei.org, serge@...lyn.com
Subject: Re: [PATCH] lockdown: ratelimit denial messages

On Fri, Sep 9, 2022 at 10:05 AM Paul Moore <paul@...l-moore.com> wrote:
> On Thu, Sep 8, 2022 at 6:02 PM Nathan Lynch <nathanl@...ux.ibm.com> wrote:
> >
> > User space can flood the log with lockdown denial messages:
> >
> > [  662.555584] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
> > [  662.563237] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
> > [  662.571134] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
> > [  662.578668] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
> > [  662.586021] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
> > [  662.593398] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
> >
> > Ratelimiting these shouldn't meaningfully degrade the quality of the
> > information logged.
> >
> > Signed-off-by: Nathan Lynch <nathanl@...ux.ibm.com>
> > ---
> >  security/lockdown/lockdown.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
>
> This seems reasonable.  While the last visible lockdown message to the
> console might be incorrect/old, I think it would give the user a good
> indication that lockdown is being hit and hopefully preserve the start
> of the denial storm.  It is also worth noting that this does introduce
> a spinlock to this code path, but since it is only an issue on error I
> doubt it will have any significant impact.
>
> I'll leave this until next week to give people a chance to
> comment/object, but if there are no further comments I'll plan on
> merging this into lsm/next.

Now merged into lsm/next, thanks!

-- 
paul-moore.com