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

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Date:   Thu, 17 Jun 2021 17:13:53 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Jonathan Liu <net147@...il.com>
Cc:     dri-devel@...ts.freedesktop.org, 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>,
        Marek Vasut <marex@...x.de>,
        Frieder Schrempf <frieder.schrempf@...tron.de>
Subject: Re: [PATCH] drm/bridge: ti-sn65dsi83: Fix null pointer dereference
 in remove callback

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 ?

> 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);
>  

-- 
Regards,

Laurent Pinchart