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Date: Tue, 26 May 2026 19:19:46 +0100
From: Jonathan Cameron <jic23@kernel.org>
To: Maxwell Doose <m32285159@gmail.com>
Cc: Dan Carpenter <error27@gmail.com>, Nuno Sa <nuno.sa@analog.com>, Olivier
 Moysan <olivier.moysan@foss.st.com>, David Lechner <dlechner@baylibre.com>,
 Andy Shevchenko <andy@kernel.org>, linux-iio@vger.kernel.org,
 linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] iio: backend: fix uninitialized data in debugfs
Message-ID: <20260526191946.409160c8@jic23-huawei>
In-Reply-To: <CAKqfh0En4pHqSfxfd2FHSDTxfWx6BfJLfeQ3xup4bwfLSTrZRA@mail.gmail.com>
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On Mon, 25 May 2026 08:20:31 -0500
Maxwell Doose <m32285159@gmail.com> wrote:

> On Mon, May 25, 2026 at 2:17=E2=80=AFAM Dan Carpenter <error27@gmail.com>=
 wrote:
> >
> > If the *ppos value is non-zero then simple_write_to_buffer() will not
> > initialize the start of the buf[] buffer.  Non-zero ppos values aren't
> > going to work at all.  Check for that at the start of the function and
> > return -EINVAL.
> > =20
>=20
> Commit message is incorrect, it looks like you're returning -ENOSPC here.=
..
Tweaked and applied to the fixes-togreg branch of iio.git + marked for stab=
le.

thanks,

J
>=20
> >
> > Fixes: cdf01e0809a4 ("iio: backend: add debugFs interface")
> > Signed-off-by: Dan Carpenter <error27@gmail.com>
> > ---
> >  drivers/iio/industrialio-backend.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industria=
lio-backend.c
> > index 138ebebc9c0d..4763e224ebc6 100644
> > --- a/drivers/iio/industrialio-backend.c
> > +++ b/drivers/iio/industrialio-backend.c
> > @@ -156,7 +156,7 @@ static ssize_t iio_backend_debugfs_write_reg(struct=
 file *file,
> >         ssize_t rc;
> >         int ret;
> >
> > -       if (count >=3D sizeof(buf))
> > +       if (*ppos !=3D 0 || count >=3D sizeof(buf))
> >                 return -ENOSPC;
> > =20
>=20
> See above comment.
>=20
> best regards,
> max
>=20
>=20
> >
> >         rc =3D simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userb=
uf, count);
> > --
> > 2.53.0
> >
> > =20