linux-kernel - Re: [PATCH v5 2/5] Smack: Prepare for PTRACE_MODE

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Date:   Tue, 16 Oct 2018 13:44:05 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Jann Horn <jannh@...gle.com>
cc:     Casey Schaufler <casey.schaufler@...el.com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        selinux@...ho.nsa.gov, Dave Hansen <dave.hansen@...el.com>,
        deneen.t.dock@...el.com, kristen@...ux.intel.com,
        Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [PATCH v5 2/5] Smack: Prepare for PTRACE_MODE_SCHED

On Thu, 4 Oct 2018, Jann Horn wrote:

> > Well, we can't really call out into audit from scheduler code, and the
> > previous versions of the patchsets didn't have PTRACE_MODE_SCHED, so it
> > had to be included in PTRACE_MODE_IBPB in order to make sure we're not
> > calling into audit from context switch code.
> >
> > Or did I misunderstand the question?
> 
> If I understand Casey correctly, he is saying that your patch
> (https://lore.kernel.org/lkml/nycvar.YFH.7.76.1809251437340.15880@cbobk.fhfr.pm/)
> doesn't include PTRACE_MODE_NOAUDIT for IBPB, but the previous v6 of
> your patch (https://lore.kernel.org/lkml/nycvar.YFH.7.76.1809121105330.15880@cbobk.fhfr.pm/)
> did include it, and therefore Casey thinks that there is a specific
> reason why you removed PTRACE_MODE_NOAUDIT, 

Quite honestly, I don't remember. I dont't think there is any deadlock 
that'd be triggered by this.

> and therefore Casey is adding special-case logic for PTRACE_MODE_SCHED 
> to Smack when simply using PTRACE_MODE_NOAUDIT would also work.
> 
> I think that Casey should change ptrace_may_access_sched() to use
> "mode | PTRACE_MODE_SCHED | PTRACE_MODE_NOAUDIT".

Agreed, that should work.

Thanks,

-- 
Jiri Kosina
SUSE Labs