linux-kernel - Re: System crash with perf

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Message-ID: <20190130223308.GA8145@krava>
Date:   Wed, 30 Jan 2019 23:33:08 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        eranian@...gle.com, vincent.weaver@...ne.edu,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Subject: Re: System crash with perf_fuzzer (kernel: 5.0.0-rc3)

On Wed, Jan 30, 2019 at 12:39:47PM -0800, Andi Kleen wrote:
> Jiri Olsa <jolsa@...hat.com> writes:
> >
> > the patch adds check_eriod pmu callback.. I need to check if there's
> > better way to do this, but so far it fixes the crash for me
> >
> > if you guys could check this patch, that'd be great
> 
> There's already a limit_period callback, perhaps that could
> be extended. But ok, can do it this way too.

right, we call it within x86_perf_event_set_period to limit
the period, but I guess we should include this check after
changing the period:

        if (event->attr.sample_period && x86_pmu.limit_period) {
                if (x86_pmu.limit_period(event, event->attr.sample_period) >
                                event->attr.sample_period)
                        return -EINVAL;
        }

> 
> I suspect there are some other cases that need this callback, not
> just BTS, e.g. the checks in hsw_hw_config

ok, the sample_period values for checkpointed events,
we should check for this as well.. I'll add that

jirka