linux-kernel - Re: [PATCH] usb/c67x00/c67x00-drv: Fix Data Race bug

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Message-ID: <CAD=jOEYCXGrsaGsZebGR56f+JDN3fH2iy=htrpprCFHKxLk8Lg@mail.gmail.com>
Date:   Fri, 28 Aug 2020 21:49:27 +0530
From:   Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     jacmet@...site.dk, linux-usb@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ldv-project@...uxtesting.org, andrianov <andrianov@...ras.ru>
Subject: Re: [PATCH] usb/c67x00/c67x00-drv: Fix Data Race bug

On Fri, Aug 28, 2020 at 1:10 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Wed, Aug 26, 2020 at 08:14:59PM +0530, madhuparnabhowmik10@...il.com wrote:
> > From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
> >
> > Currently in c67x00_drv_probe() IRQ is requested before calling
> > c67x00_probe_sie() and hence if interrupt happens the reading of certain
> > variables in the handler can race with initialization of the variables,
> > for e.g. sie->sie_num is written in c67x00_probe_sie() and read in
> >  c67x00_hcd_irq().
> > Hence, this patch calls c67x00_probe_sie() before requesting IRQ in
> > probe.
> >
> > Found by Linux Driver Verification project (linuxtesting.org).
> >
> > Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
> > ---
> >  drivers/usb/c67x00/c67x00-drv.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/usb/c67x00/c67x00-drv.c b/drivers/usb/c67x00/c67x00-drv.c
> > index 53838e7d4eef..2e816d5ca0eb 100644
> > --- a/drivers/usb/c67x00/c67x00-drv.c
> > +++ b/drivers/usb/c67x00/c67x00-drv.c
> > @@ -146,6 +146,9 @@ static int c67x00_drv_probe(struct platform_device *pdev)
> >       c67x00_ll_init(c67x00);
> >       c67x00_ll_hpi_reg_init(c67x00);
> >
> > +     for (i = 0; i < C67X00_SIES; i++)
> > +             c67x00_probe_sie(&c67x00->sie[i], c67x00, i);
> > +
> >       ret = request_irq(res2->start, c67x00_irq, 0, pdev->name, c67x00);
> >       if (ret) {
> >               dev_err(&pdev->dev, "Cannot claim IRQ\n");
> > @@ -158,9 +161,6 @@ static int c67x00_drv_probe(struct platform_device *pdev)
> >               goto reset_failed;
> >       }
> >
> > -     for (i = 0; i < C67X00_SIES; i++)
> > -             c67x00_probe_sie(&c67x00->sie[i], c67x00, i);
> > -
> >       platform_set_drvdata(pdev, c67x00);
> >
> >       return 0;
>
> Have you tested this on hardware to verify it works properly?

No, I haven't, don't think I have the relevant hardware.
It would be great if someone could test this and add a Tested-by tag.

Thanks,
Madhuparna

>
> thanks,
>
> greg k-h