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Date:   Sun, 17 Oct 2021 17:15:03 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Yang Yingliang <yangyingliang@...wei.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "alexandru.ardelean@...log.com" <alexandru.ardelean@...log.com>
Subject: Re: [PATCH v3] iio: core: fix double free in
 iio_device_unregister_sysfs()

On Wed, 13 Oct 2021 08:51:38 +0300
Andy Shevchenko <andy.shevchenko@...il.com> wrote:

> On Wednesday, October 13, 2021, Andy Shevchenko <andy.shevchenko@...il.com>
> wrote:
> 
> >
> >
> > On Wednesday, October 13, 2021, Yang Yingliang <yangyingliang@...wei.com>
> > wrote:
> >  
> >> I got the double free report:
> >>
> >> BUG: KASAN: double-free or invalid-free in kfree+0xce/0x390  
> >
> >
> >  
> >>  kfree+0xce/0x390  
> >
> >
> >
> > This line also redundant, but no need to resend, I hope Jonathan can do it
> > for you.
> >
> >  
> >>  iio_device_unregister_sysfs+0x108/0x13b [industrialio]
> >>  iio_dev_release+0x9e/0x10e [  
> >
> >  
> >>  
> 
> 
> >  
> >>  device_release+0xa5/0x240
> >>  kobject_put+0x1e5/0x540
> >>  put_device+0x20/0x30
> >>  devm_iio_device_release+0x21/0x30 [industrialio]  
> >
> >  
> >>  
> Actually above lines are also part of the noise
Not sure I'm quite so keen to strip everything back completely (though I do
agree keeping it fairly minimal is good.

Anyhow, tidied it up a bit and applied.  I also added a note that more
radical surgery is needed to clean up the lifetime management but in the
meantime this deals with the symptoms.

Applied to the fixes-togreg branch of iio.git and marked for stable.

Thanks,

Jonathan

> 
> 
> >  
> >> If __iio_device_register() fails, iio_dev_opaque->groups will be freed
> >> in error path in iio_device_unregister_sysfs(), then iio_dev_release()
> >> will call iio_device_unregister_sysfs() again, it causes double free.
> >> Set iio_dev_opaque->groups to NULL when it's freed to fix this double
> >> free.
> >>
> >> Fixes: 32f171724e5c ("iio: core: rework iio device group creation")
> >> Reported-by: Hulk Robot <hulkci@...wei.com>
> >> Reviewed-by: Alexandru Ardelean <ardeleanalex@...il.com>
> >> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
> >> ---
> >> v1 -> v3:
> >>   reduce some backtrace in commit message
> >> ---
> >>  drivers/iio/industrialio-core.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/drivers/iio/industrialio-core.c
> >> b/drivers/iio/industrialio-core.c
> >> index 2dbb37e09b8c..2dc837db50f7 100644
> >> --- a/drivers/iio/industrialio-core.c
> >> +++ b/drivers/iio/industrialio-core.c
> >> @@ -1600,6 +1600,7 @@ static void iio_device_unregister_sysfs(struct
> >> iio_dev *indio_dev)
> >>         kfree(iio_dev_opaque->chan_attr_group.attrs);
> >>         iio_dev_opaque->chan_attr_group.attrs = NULL;
> >>         kfree(iio_dev_opaque->groups);
> >> +       iio_dev_opaque->groups = NULL;
> >>  }
> >>
> >>  static void iio_dev_release(struct device *device)
> >> --
> >> 2.25.1  
> >
> >  
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> >
> > --
> > With Best Regards,
> > Andy Shevchenko
> >
> >
> >  
> 

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