linux-kernel - Re: [PATCH v3] lockdown,selinux: fix wrong subject in some SELinux lockdown checks

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Message-ID: <CAHC9VhReGcV=cngDMmAcEiS2NpkXZQ6b09go9m0omzxLdrUQXg@mail.gmail.com>
Date:   Tue, 31 Aug 2021 14:59:31 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Ondrej Mosnacek <omosnace@...hat.com>,
        Linux Security Module list 
        <linux-security-module@...r.kernel.org>,
        James Morris <jmorris@...ei.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        SElinux list <selinux@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        X86 ML <x86@...nel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        linux-cxl@...r.kernel.org, linux-efi <linux-efi@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux-pm mailing list <linux-pm@...r.kernel.org>,
        linux-serial@...r.kernel.org, bpf <bpf@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>,
        Kexec Mailing List <kexec@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v3] lockdown,selinux: fix wrong subject in some SELinux
 lockdown checks

On Tue, Aug 31, 2021 at 2:58 PM Dan Williams <dan.j.williams@...el.com> wrote:
> On Tue, Aug 31, 2021 at 6:53 AM Paul Moore <paul@...l-moore.com> wrote:
> > On Tue, Aug 31, 2021 at 5:09 AM Ondrej Mosnacek <omosnace@...hat.com> wrote:
> > > On Sat, Jun 19, 2021 at 12:18 AM Dan Williams <dan.j.williams@...el.com> wrote:
> > > > On Wed, Jun 16, 2021 at 1:51 AM Ondrej Mosnacek <omosnace@...hat.com> wrote:
> >
> > ...
> >
> > > > > diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> > > > > index 2acc6173da36..c1747b6555c7 100644
> > > > > --- a/drivers/cxl/mem.c
> > > > > +++ b/drivers/cxl/mem.c
> > > > > @@ -568,7 +568,7 @@ static bool cxl_mem_raw_command_allowed(u16 opcode)
> > > > >         if (!IS_ENABLED(CONFIG_CXL_MEM_RAW_COMMANDS))
> > > > >                 return false;
> > > > >
> > > > > -       if (security_locked_down(LOCKDOWN_NONE))
> > > > > +       if (security_locked_down(current_cred(), LOCKDOWN_NONE))
> > > >
> > > > Acked-by: Dan Williams <dan.j.williams@...el.com>
> > > >
> > > > ...however that usage looks wrong. The expectation is that if kernel
> > > > integrity protections are enabled then raw command access should be
> > > > disabled. So I think that should be equivalent to LOCKDOWN_PCI_ACCESS
> > > > in terms of the command capabilities to filter.
> > >
> > > Yes, the LOCKDOWN_NONE seems wrong here... but it's a pre-existing bug
> > > and I didn't want to go down yet another rabbit hole trying to fix it.
> > > I'll look at this again once this patch is settled - it may indeed be
> > > as simple as replacing LOCKDOWN_NONE with LOCKDOWN_PCI_ACCESS.
> >
> > At this point you should be well aware of my distaste for merging
> > patches that have known bugs in them.  Yes, this is a pre-existing
> > condition, but it seems well within the scope of this work to address
> > it as well.
> >
> > This isn't something that is going to get merged while the merge
> > window is open, so at the very least you've got almost two weeks to
> > sort this out - please do that.
>
> Yes, apologies, I should have sent the fix shortly after noticing the
> problem. I'll get the CXL bug fix out of the way so Ondrej can move
> this along.

Thanks Dan.

-- 
paul moore
www.paul-moore.com