Messages in this thread | | | Date | Thu, 6 Jul 2017 16:53:40 -0700 (PDT) | From | Shivappa Vikas <> | Subject | Re: [PATCH 21/21] x86/intel_rdt/mbm: Handle counter overflow |
| |
On Sun, 2 Jul 2017, Thomas Gleixner wrote:
> On Mon, 26 Jun 2017, Vikas Shivappa wrote: >> +static void mbm_update(struct rdt_domain *d, int rmid) >> +{ >> + struct rmid_read rr; >> + >> + rr.first = false; >> + rr.d = d; >> + >> + if (is_mbm_total_enabled()) { >> + rr.evtid = QOS_L3_MBM_TOTAL_EVENT_ID; >> + __mon_event_count(rmid, &rr); > > This is broken as it is not protected against a concurrent read from user > space which comes in via a smp function call.
The read from user also has the rdtgroup_mutex.
Thanks, Vikas
> > This means both the internal state and __rmid_read() are unprotected. > > I'm not sure whether it's enough to disable interrupts around > __mon_event_count(), but that's the minimal protection required. It's > definitely good enough for __rmid_read(), but it might not be sufficient > for protecting domain->mbm_[local|total]. I leave the exercise of figuring > that out to you. > > Thanks, > > tglx >
| |