linux-kernel - Re: [PATCH] perf/core: fix unconditional security_locked

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Date:   Tue, 16 Mar 2021 11:12:23 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ondrej Mosnacek <omosnace@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>, selinux@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
        Matthew Garrett <mjg59@...gle.com>
Subject: Re: [PATCH] perf/core: fix unconditional security_locked_down() call

On Tue, Mar 16, 2021 at 10:30 AM Peter Zijlstra <peterz@...radead.org> wrote:
> On Tue, Mar 16, 2021 at 09:53:21AM -0400, Paul Moore wrote:
> > On Wed, Feb 24, 2021 at 4:59 PM Ondrej Mosnacek <omosnace@...hat.com> wrote:
> > >
> > > Currently, the lockdown state is queried unconditionally, even though
> > > its result is used only if the PERF_SAMPLE_REGS_INTR bit is set in
> > > attr.sample_type. While that doesn't matter in case of the Lockdown LSM,
> > > it causes trouble with the SELinux's lockdown hook implementation.
> > >
> > > SELinux implements the locked_down hook with a check whether the current
> > > task's type has the corresponding "lockdown" class permission
> > > ("integrity" or "confidentiality") allowed in the policy. This means
> > > that calling the hook when the access control decision would be ignored
> > > generates a bogus permission check and audit record.
> > >
> > > Fix this by checking sample_type first and only calling the hook when
> > > its result would be honored.
> > >
> > > Fixes: b0c8fdc7fdb7 ("lockdown: Lock down perf when in confidentiality mode")
> > > Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>
> > > ---
> > >  kernel/events/core.c | 12 ++++++------
> > >  1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > Perf/core folks, do you want to pull this in via your tree?  If I
> > don't hear anything in the next day I'll pull this in via the
> > selinux/next tree.
> >
> > Reviewed-by: Paul Moore <paul@...l-moore.com>
>
> Ah, fell in the cracks... I've no idea what Changelog is trying to tell
> me. It is pure gibberish to me. But the patch seems harmless enough to me.
>
> Let me queue it then.

Great, thanks.

-- 
paul moore
www.paul-moore.com