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

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Message-ID: <CALAqxLX06tFkj7DVrPDJMB3C0-N5jqpFY-J4nS0i+r7GBhGkhw@mail.gmail.com>
Date:   Mon, 29 Aug 2016 11:28:47 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     lkml <linux-kernel@...r.kernel.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        Kees Cook <keescook@...omium.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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 Mon, Aug 22, 2016 at 4:01 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

Ping? Any feedback or comments on this one?

thanks
-john