Messages in this thread |  | | Date | Tue, 4 Sep 2018 15:47:48 +0200 | From | Juri Lelli <> | Subject | Re: [PATCH v4 14/16] sched/core: uclamp: request CAP_SYS_ADMIN by default |
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Hi,
On 28/08/18 14:53, Patrick Bellasi wrote: > The number of clamp groups supported is limited and defined at compile > time. However, a malicious user can currently ask for many different
Even if not malicious.. :-)
> clamp values thus consuming all the available clamp groups. > > Since on properly configured systems we expect only a limited set of > different clamp values, the previous problem can be mitigated by > allowing access to clamp groups configuration only to privileged tasks. > This should still allow a System Management Software to properly > pre-configure the system. > > Let's restrict the tuning of utilization clamp values, by default, to > tasks with CAP_SYS_ADMIN capabilities. > > Whenever this should be considered too restrictive and/or not required > for a specific platforms, a kernel boot option is provided to change > this default behavior thus allowing non privileged tasks to change their > utilization clamp values. > > Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Cc: Paul Turner <pjt@google.com> > Cc: Suren Baghdasaryan <surenb@google.com> > Cc: Todd Kjos <tkjos@google.com> > Cc: Joel Fernandes <joelaf@google.com> > Cc: Steve Muckle <smuckle@google.com> > Cc: Juri Lelli <juri.lelli@redhat.com> > Cc: Quentin Perret <quentin.perret@arm.com> > Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> > Cc: Morten Rasmussen <morten.rasmussen@arm.com> > Cc: linux-kernel@vger.kernel.org > Cc: linux-pm@vger.kernel.org > > --- > Changes in v4: > Others: > - new patch added in this version > - rebased on v4.19-rc1 > --- > .../admin-guide/kernel-parameters.txt | 3 +++ > kernel/sched/core.c | 22 ++++++++++++++++--- > 2 files changed, 22 insertions(+), 3 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 9871e649ffef..481f8214ea9a 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -4561,6 +4561,9 @@ > <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> > See also Documentation/input/devices/joystick-parport.rst > > + uclamp_user [KNL] Enable task-specific utilization clamping tuning > + also from tasks without CAP_SYS_ADMIN capability. > + > udbg-immortal [PPC] When debugging early kernel crashes that > happen after console_init() and before a proper > console driver takes over, this boot options might > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 222397edb8a7..8341ce580a9a 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1510,14 +1510,29 @@ static inline int alloc_uclamp_sched_group(struct task_group *tg, > static inline void free_uclamp_sched_group(struct task_group *tg) { } > #endif /* CONFIG_UCLAMP_TASK_GROUP */ > > +static bool uclamp_user_allowed __read_mostly; > +static int __init uclamp_user_allow(char *str) > +{ > + uclamp_user_allowed = true; > + > + return 0; > +} > +early_param("uclamp_user", uclamp_user_allow); > + > static inline int __setscheduler_uclamp(struct task_struct *p, > - const struct sched_attr *attr) > + const struct sched_attr *attr, > + bool user)
Wondering if you want to fold the check below inside the
if (user && !capable(CAP_SYS_NICE)) { ... }
block. It would also save you from adding another parameter to the function.
> { > int group_id[UCLAMP_CNT] = { UCLAMP_NOT_VALID }; > int lower_bound, upper_bound; > struct uclamp_se *uc_se; > int result = 0; > > + if (!capable(CAP_SYS_ADMIN) && > + user && !uclamp_user_allowed) { > + return -EPERM; > + } > +
Best,
- Juri
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