linux-kernel - Re: [PATCH] media: renesas: rzg2l-cru: Fix possible ERR_PTR dereference in rzg2l_cru_get_virtual

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Message-ID: <CAGpma=5i21ObECvQL9EZRQUJ3rfXTZ=78CFkFtLmwoq+Te7c1w@mail.gmail.com>
Date: Sat, 27 Dec 2025 18:33:56 +0300
From: Alper Ak <alperyasinak1@...il.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: mchehab@...nel.org, hverkuil+cisco@...nel.org, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>, 
	Tommaso Merciai <tommaso.merciai.xr@...renesas.com>, 
	Daniel Scally <dan.scally+renesas@...asonboard.com>, Biju Das <biju.das.jz@...renesas.com>, 
	Jacopo Mondi <jacopo.mondi@...asonboard.com>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: renesas: rzg2l-cru: Fix possible ERR_PTR
 dereference in rzg2l_cru_get_virtual_channel()

> What makes you think this can happen ?

media_pad_remote_pad_unique() explicitly documents that it can return
-ENOTUNIQ when multiple links are enabled and -ENOLINK when no connected
pad is found.

The return value is dereferenced immediately via remote_pad->index in
the v4l2_subdev_call() without any error check.

While these situations may not occur for this driver, I have
seen other media drivers perform IS_ERR() checks after calling the same
function, so adding the same defensive handling here would be
consistent with existing usage.


Laurent Pinchart <laurent.pinchart@...asonboard.com>, 27 Ara 2025 Cmt,
16:05 tarihinde şunu yazdı:
>
> On Sat, Dec 27, 2025 at 03:19:44PM +0300, Alper Ak wrote:
> > media_pad_remote_pad_unique() can return ERR_PTR(-ENOTUNIQ) or
> > ERR_PTR(-ENOLINK) on error situation.
> >
> > The current code dereferences remote_pad without checking for
> > these error cases, which could lead to invalid memory access.
>
> What makes you think this can happen ?
>
> > Add IS_ERR() check before dereferencing the pointer.
> >
> > Fixes: d7d72dae81d5 ("media: rzg2l-cru: Retrieve virtual channel information")
> > Signed-off-by: Alper Ak <alperyasinak1@...il.com>
> > ---
> >  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > index 162e2ace6931..bf7d96841c78 100644
> > --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> > @@ -411,6 +411,9 @@ static int rzg2l_cru_get_virtual_channel(struct rzg2l_cru_dev *cru)
> >       int ret;
> >
> >       remote_pad = media_pad_remote_pad_unique(&cru->ip.pads[RZG2L_CRU_IP_SINK]);
> > +     if (IS_ERR(remote_pad))
> > +             return PTR_ERR(remote_pad);
> > +
> >       ret = v4l2_subdev_call(cru->ip.remote, pad, get_frame_desc, remote_pad->index, &fd);
> >       if (ret < 0 && ret != -ENOIOCTLCMD) {
> >               dev_err(cru->dev, "get_frame_desc failed on IP remote subdev\n");
>
> --
> Regards,
>
> Laurent Pinchart