Re: [PATCH] iio: buffer: serialize buffer teardown with mode claims

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 24 Sep 2026 09:24:33 +0100
Nuno Sá <nuno.sa@analog.com> wrote:

> On Mon, Sep 21, 2026 at 03:24:21PM +0900, Jinseob Kim wrote:
> > Buffer-mode claims hold mlock to guarantee that the device remains in
> > buffer mode until the claim is released. Normal buffer updates take
> > info_exist_lock followed by mlock in iio_update_buffers().
> > 
> > However, iio_device_unregister() disables and deactivates all buffers
> > without taking mlock. This can invalidate buffer state, including
> > active_scan_mask, while a buffer-mode claim is held.
> > 
> > Take mlock in iio_disable_all_buffers() so that unregister honors the
> > mode-claim lifetime guarantee. The info_exist_lock -> mlock ordering
> > matches iio_update_buffers().
> > 
> > Fixes: 0a8565425afd ("iio: core: introduce iio_device_{claim|release}_buffer_mode() APIs")
> > Suggested-by: Jonathan Cameron <jic23@kernel.org>
> > Signed-off-by: Jinseob Kim <kimjinseob88@gmail.com>
> > ---  
> 
> Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Applied to the fixes-togreg branch of iio.git and marked for
stable inclusion. It should be safe enough but I do want to get
some testing on this. Crossed fingers!

Thanks,

Jonathan

> 
> >  drivers/iio/industrialio-buffer.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> > index 2c9ec93dff47..d60bad5492e7 100644
> > --- a/drivers/iio/industrialio-buffer.c
> > +++ b/drivers/iio/industrialio-buffer.c
> > @@ -1377,6 +1377,10 @@ EXPORT_SYMBOL_GPL(iio_update_buffers);
> >  
> >  void iio_disable_all_buffers(struct iio_dev *indio_dev)
> >  {
> > +	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> > +
> > +	guard(mutex)(&iio_dev_opaque->mlock);
> > +
> >  	iio_disable_buffers(indio_dev);
> >  	iio_buffer_deactivate_all(indio_dev);
> >  }
> > 
> > base-commit: dceba8e581e3e8f475da0efbd7a73f3d9524ddd2
> > -- 
> > 2.43.0
> >