linux-kernel - Re: [PATCH] drm/bridge: ti-sn65dsi83: Fix null pointer dereference in remove callback

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Date:   Fri, 18 Jun 2021 13:06:07 +1000
From:   Jonathan Liu <net147@...il.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Marek Vasut <marex@...x.de>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Linus Walleij <linus.walleij@...aro.org>,
        Frieder Schrempf <frieder.schrempf@...tron.de>
Subject: Re: [PATCH] drm/bridge: ti-sn65dsi83: Fix null pointer dereference in
 remove callback

Hi Marek,

On Fri, 18 Jun 2021 at 00:14, Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Jonathan,
>
> Thank you for the patch.
>
> On Thu, Jun 17, 2021 at 09:19:25PM +1000, Jonathan Liu wrote:
> > If attach has not been called, unloading the driver can result in a null
> > pointer dereference in mipi_dsi_detach as ctx->dsi has not been assigned
> > yet.
>
> Shouldn't this be done in a brige .detach() operation instead ?
>

Could you please take a look?
I don't have a working setup to test moving the code to detach.

> > Fixes: ceb515ba29ba6b ("drm/bridge: ti-sn65dsi83: Add TI SN65DSI83 and SN65DSI84 driver")
> > Signed-off-by: Jonathan Liu <net147@...il.com>
> > ---
> >  drivers/gpu/drm/bridge/ti-sn65dsi83.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> > index 750f2172ef08..8e9f45c5c7c1 100644
> > --- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> > @@ -671,8 +671,11 @@ static int sn65dsi83_remove(struct i2c_client *client)
> >  {
> >       struct sn65dsi83 *ctx = i2c_get_clientdata(client);
> >
> > -     mipi_dsi_detach(ctx->dsi);
> > -     mipi_dsi_device_unregister(ctx->dsi);
> > +     if (ctx->dsi) {
> > +             mipi_dsi_detach(ctx->dsi);
> > +             mipi_dsi_device_unregister(ctx->dsi);
> > +     }
> > +
> >       drm_bridge_remove(&ctx->bridge);
> >       of_node_put(ctx->host_node);
> >

Thanks.

Regards,
Jonathan