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From: John Stultz <john.stultz@linaro.org>
Date: Tue, 7 Feb 2017 20:29:31 -0800
Message-ID: <CALAqxLW6FowGNWgtnSh6S9B4S_C=GW29mq7uLvk=_KMceOfHSw@mail.gmail.com>
Subject: Re: [PATCH] time: Remove CONFIG_TIMER_STATS
To: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, Xing Gao <xgao01@email.wm.edu>,
        Jessica Frazelle <me@jessfraz.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Jonathan Corbet <corbet@lwn.net>, Tejun Heo <tj@kernel.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>, Petr Mladek <pmladek@suse.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>,
        Nicolas Iooss <nicolas.iooss_linux@m4x.org>,
        Nicolas Pitre <nicolas.pitre@linaro.org>,
        Richard Cochran <richardcochran@gmail.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Michal Marek <mmarek@suse.com>, Josh Poimboeuf <jpoimboe@redhat.com>,
        Dmitry Vyukov <dvyukov@google.com>, Olof Johansson <olof@lixom.net>,
        Shuah Khan <shuah@kernel.org>, linux-doc@vger.kernel.org,
        lkml <linux-kernel@vger.kernel.org>,
        kernel-hardening@lists.openwall.com
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On Tue, Feb 7, 2017 at 3:40 PM, Kees Cook <keescook@chromium.org> wrote:
> Currently CONFIG_TIMER_STATS exposes process information across namespaces:
>
> kernel/time/timer_list.c print_timer():
>
>         SEQ_printf(m, ", %s/%d", tmp, timer->start_pid);
>
> /proc/timer_list:
>
>  #11: <0000000000000000>, hrtimer_wakeup, S:01, do_nanosleep, cron/2570
>
> Given that the tracer can give the same information, this patch entirely
> removes CONFIG_TIMER_STATS.
>
> Suggested-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Kees Cook <keescook@chromium.org>

I don't have an issue with this, but I worry this would break some
tooling out there. Should it be marked as deprecated first?

Or maybe just pulling the band-aid off is the best way?

thanks
-john

From mboxrd@z Thu Jan  1 00:00:00 1970
MIME-Version: 1.0
In-Reply-To: <20170207234031.GA27933@beast>
References: <20170207234031.GA27933@beast>
From: John Stultz <john.stultz@linaro.org>
Date: Tue, 7 Feb 2017 20:29:31 -0800
Message-ID: <CALAqxLW6FowGNWgtnSh6S9B4S_C=GW29mq7uLvk=_KMceOfHSw@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Subject: [kernel-hardening] Re: [PATCH] time: Remove CONFIG_TIMER_STATS
To: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, Xing Gao <xgao01@email.wm.edu>, Jessica Frazelle <me@jessfraz.com>, "Eric W. Biederman" <ebiederm@xmission.com>, Jonathan Corbet <corbet@lwn.net>, Tejun Heo <tj@kernel.org>, Lai Jiangshan <jiangshanlai@gmail.com>, Petr Mladek <pmladek@suse.com>, Andrew Morton <akpm@linux-foundation.org>, Oleg Nesterov <oleg@redhat.com>, Nicolas Iooss <nicolas.iooss_linux@m4x.org>, Nicolas Pitre <nicolas.pitre@linaro.org>, Richard Cochran <richardcochran@gmail.com>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Michal Marek <mmarek@suse.com>, Josh Poimboeuf <jpoimboe@redhat.com>, Dmitry Vyukov <dvyukov@google.com>, Olof Johansson <olof@lixom.net>, Shuah Khan <shuah@kernel.org>, linux-doc@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>, kernel-hardening@lists.openwall.com
List-ID: <kernel-hardening.lists.openwall.com>

On Tue, Feb 7, 2017 at 3:40 PM, Kees Cook <keescook@chromium.org> wrote:
> Currently CONFIG_TIMER_STATS exposes process information across namespaces:
>
> kernel/time/timer_list.c print_timer():
>
>         SEQ_printf(m, ", %s/%d", tmp, timer->start_pid);
>
> /proc/timer_list:
>
>  #11: <0000000000000000>, hrtimer_wakeup, S:01, do_nanosleep, cron/2570
>
> Given that the tracer can give the same information, this patch entirely
> removes CONFIG_TIMER_STATS.
>
> Suggested-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Kees Cook <keescook@chromium.org>

I don't have an issue with this, but I worry this would break some
tooling out there. Should it be marked as deprecated first?

Or maybe just pulling the band-aid off is the best way?

thanks
-john