linux-kernel - Re: [RESEND][PATCH] proc: Fix timerslack_ns CAP_SYS

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Message-Id: <20160830160606.9088798dc1ec62105ae19b78@linux-foundation.org>
Date:   Tue, 30 Aug 2016 16:06:06 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Oren Laadan <orenl@...lrox.com>,
        Ruchi Kandoi <kandoiruchi@...gle.com>,
        Rom Lemarchand <romlem@...roid.com>,
        Todd Kjos <tkjos@...gle.com>, Colin Cross <ccross@...roid.com>,
        Nick Kralevich <nnk@...gle.com>,
        Dmitry Shmidt <dimitrysh@...gle.com>,
        Elliott Hughes <enh@...gle.com>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [RESEND][PATCH] proc: Fix timerslack_ns CAP_SYS_NICE check when
 adjusting self

On Tue, 30 Aug 2016 18:46:23 -0400 Kees Cook <keescook@...omium.org> wrote:

> On Mon, Aug 22, 2016 at 7:01 PM, John Stultz <john.stultz@...aro.org> wrote:
> > In changing from checking ptrace_may_access(p, PTRACE_MODE_ATTACH_FSCREDS)
> > to capable(CAP_SYS_NICE), I missed that ptrace_my_access succeeds
> > when p == current, but the CAP_SYS_NICE doesn't.
> >
> > Thus while the previous commit was intended to loosen the needed
> > privledges to modify a processes timerslack, it needlessly restricted
> > a task modifying its own timerslack via the proc/<tid>/timerslack_ns
> > (which is permitted also via the PR_SET_TIMERSLACK method).
> >
> > This patch corrects this by checking if p == current before checking
> > the CAP_SYS_NICE value.
> >
> > This patch applies on top of my two previous patches currently in -mm
> >
> > Cc: Kees Cook <keescook@...omium.org>
> > Cc: "Serge E. Hallyn" <serge@...lyn.com>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > CC: Arjan van de Ven <arjan@...ux.intel.com>
> > Cc: Oren Laadan <orenl@...lrox.com>
> > Cc: Ruchi Kandoi <kandoiruchi@...gle.com>
> > Cc: Rom Lemarchand <romlem@...roid.com>
> > Cc: Todd Kjos <tkjos@...gle.com>
> > Cc: Colin Cross <ccross@...roid.com>
> > Cc: Nick Kralevich <nnk@...gle.com>
> > Cc: Dmitry Shmidt <dimitrysh@...gle.com>
> > Cc: Elliott Hughes <enh@...gle.com>
> > Cc: Android Kernel Team <kernel-team@...roid.com>
> > Acked-by: Kees Cook <keescook@...omium.org>
> > Signed-off-by: John Stultz <john.stultz@...aro.org>
> 
> Andrew, can you take this for v4.8?

Well, it fixes
proc-relax-proc-tid-timerslack_ns-capability-requirements.patch,
somewhat.  And it textually depends on that.

Do we want all of

proc-relax-proc-tid-timerslack_ns-capability-requirements.patch
proc-add-lsm-hook-checks-to-proc-tid-timerslack_ns.patch
proc-fix-timerslack_ns-cap_sys_nice-check-when-adjusting-self.patch

in 4.8?  If so, why?