linux-kernel - Re: [REGRESSION][v4.14.y][v4.15] x86/intel_rdt/cqm: Improve limbo list processing

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Message-ID: <alpine.DEB.2.20.1801161409120.1823@nanos>
Date:   Tue, 16 Jan 2018 14:09:49 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Joseph Salisbury <joseph.salisbury@...onical.com>
cc:     vikas.shivappa@...ux.intel.com, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org, ravi.v.shankar@...el.com,
        tony.luck@...el.com, fenghua.yu@...el.com, peterz@...radead.org,
        eranian@...gle.com, ak@...ux.intel.com, davidcc@...gle.com,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        1733662@...s.launchpad.net,
        "Roderick W. Smith" <rod.smith@...onical.com>
Subject: Re: [REGRESSION][v4.14.y][v4.15] x86/intel_rdt/cqm: Improve limbo
 list processing


Vikas, Fenghua can you please look at that ASAP?

On Sun, 14 Jan 2018, Thomas Gleixner wrote:

> On Fri, 12 Jan 2018, Joseph Salisbury wrote:
> 
> > Hi Vikas,
> > 
> > A kernel bug report was opened against Ubuntu [0].  After a kernel
> > bisect, it was found that reverting the following commit resolved this bug:
> > 
> > commit 24247aeeabe99eab13b798ccccc2dec066dd6f07
> > Author: Vikas Shivappa <vikas.shivappa@...ux.intel.com>
> > Date:   Tue Aug 15 18:00:43 2017 -0700
> > 
> >     x86/intel_rdt/cqm: Improve limbo list processing
> > 
> > 
> > The regression was introduced as of v4.14-r1 and still exists with
> > current mainline.  The trace with v4.15-rc7 is in comment #44[1].
> > 
> > I was hoping to get your feedback, since you are the patch author.  Do
> > you think gathering any additional data will help diagnose this issue,
> > or would it be best to submit a revert request?
> 
> That stinks like a use after free. Can you run with KASAN enabled?
> 
> Thanks,
> 
> 	tglx