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

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Date:   Tue, 16 Mar 2021 15:30:46 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Paul Moore <paul@...l-moore.com>
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 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.