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

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Message-ID: <20251227155918.GM4094@pendragon.ideasonboard.com>
Date: Sat, 27 Dec 2025 17:59:18 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Alper Ak <alperyasinak1@...il.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()

On Sat, Dec 27, 2025 at 06:33:56PM +0300, Alper Ak wrote:
> > 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.

Unless there's a situation where an error can be returned by that
function in this driver, I don't see a need for this change. If it's not
broken, don't fix it.

> Laurent Pinchart, 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