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From:   Shakeel Butt <shakeelb@google.com>
Date:   Thu, 2 Jan 2020 08:52:21 -0800
Message-ID: <CALvZod6Tt=-8QsXy1qR-xEnitF4peWhRsUN9n1EkPpSvBXdy9g@mail.gmail.com>
Subject: Re: [PATCH v2] x86/resctrl: Fix potential memory leak
To:     Borislav Petkov <bp@alien8.de>
Cc:     Reinette Chatre <reinette.chatre@intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, x86@kernel.org,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, Jan 1, 2020 at 2:17 AM Borislav Petkov <bp@alien8.de> wrote:
>
> On Fri, Dec 20, 2019 at 08:43:58AM -0800, Shakeel Butt wrote:
> > The set_cache_qos_cfg() is leaking memory when the given level is not
> > RDT_RESOURCE_L3 or RDT_RESOURCE_L2. However at the moment, this function
> > is called with only valid levels but to make it more robust and future
> > proof, we should be handling the error path gracefully.
> >
> > Fixes: 99adde9b370de ("x86/intel_rdt: Enable L2 CDP in MSR IA32_L2_QOS_CFG")
> > Signed-off-by: Shakeel Butt <shakeelb@google.com>
> > Acked-by: Fenghua Yu <fenghua.yu@intel.com>
> > ---
> > Changes since v1:
> > - Updated the commit message
> >
> >
> >  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > index 2e3b06d6bbc6..a0c279c7f4b9 100644
> > --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > @@ -1748,8 +1748,10 @@ static int set_cache_qos_cfg(int level, bool enable)
> >               update = l3_qos_cfg_update;
> >       else if (level == RDT_RESOURCE_L2)
> >               update = l2_qos_cfg_update;
> > -     else
> > +     else {
> > +             free_cpumask_var(cpu_mask);
> >               return -EINVAL;
> > +     }
>
> And why can't the level check happen first and the allocation second,
> thus needing to allocate the cpu mask only when the level is valid?
>

We definitely can. Will send the v3 patch.

Shakeel