Messages in this thread | | | Subject | Re: [PATCH 2/2] proc: Add /proc/<pid>/timerslack_ns interface | From | Arjan van de Ven <> | Date | Thu, 14 Jul 2016 10:48:17 -0700 |
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On 7/14/2016 10:45 AM, Kees Cook wrote: > On Thu, Jul 14, 2016 at 9:09 AM, John Stultz <john.stultz@linaro.org> wrote: >> On Thu, Jul 14, 2016 at 5:48 AM, Serge E. Hallyn <serge@hallyn.com> wrote: >>> Quoting Kees Cook (keescook@chromium.org): >>>> I think the original CAP_SYS_NICE should be fine. A malicious >>>> CAP_SYS_NICE process can do plenty of insane things, I don't feel like >>>> the timer slack adds to any realistic risks. >>> >>> Can someone give a detailed explanation of what you could do with >>> the new timerslack feature and compare it to what you can do with >>> sys_nice? >> >> Looking at the man page for CAP_SYS_NICE, it looks like such a task >> can set a task as SCHED_FIFO, so they could fork some spinning >> processes and set them all SCHED_FIFO 99, in effect delaying all other >> tasks for an infinite amount of time. >> >> So one might argue setting large timerslack vlaues isn't that >> different risk wise? > > Right -- you can hose a system with CAP_SYS_NICE already; I don't > think timerslack realistically changes that.
fair enough
the worry of being able to time attack things is there already with the SCHED_FIFO so... purist objection withdrawn in favor of the pragmatic
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