Re: [PATCH v5 1/3] drm: adv7511: Fix use-after-free in adv7533_attach_dsi()

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Biju,

Thank you for the patch.

On Tue, Nov 19, 2024 at 01:10:03PM +0000, Biju Das wrote:
> The host_node pointer was assigned and freed in adv7533_parse_dt(), and
> later, adv7533_attach_dsi() uses the same. Fix this use-after-free issue
> by dropping of_node_put() in adv7533_parse_dt() and calling of_node_put()
> in error path of probe() and also in the remove().
> 
> Fixes: 1e4d58cd7f88 ("drm/bridge: adv7533: Create a MIPI DSI device")
> Cc: stable@vger.kernel.org
> Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
> ---
> Changes in v5:
>  - Updated commit description.
>  - restored host_node in struct adv7511.
>  - Dropped of_node_put() in adv7533_parse_dt() and calling of_node_put()
>    in error path of probe() and also in the remove().
> Changes in v4:
>  - Updated commit description.
>  - Dropped host_node from struct adv7511 and instead used a local pointer
>    in probe(). Also freeing of host_node pointer after use is done in
>    probe().
> Changes in v3:
>  - Replace __free construct with readable of_node_put().
> Changes in v2:
>  - Added the tag "Cc: stable@vger.kernel.org" in the sign-off area.
>  - Dropped Archit Taneja invalid Mail address
> ---
>  drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 5 +++++
>  drivers/gpu/drm/bridge/adv7511/adv7533.c     | 2 --
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> index eb5919b38263..6cfdda04f52f 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> @@ -1363,6 +1363,8 @@ static int adv7511_probe(struct i2c_client *i2c)
>  	i2c_unregister_device(adv7511->i2c_edid);
>  uninit_regulators:
>  	adv7511_uninit_regulators(adv7511);
> +	if (adv7511->host_node)
> +		of_node_put(adv7511->host_node);

This won't be called when adv7511_init_regulators() fails as the driver
returns directly then, leaking the reference. You need a new error label
and a goto for that error path.

In the future, when touching error handling, please try to check
existing error paths and verify they're still right.

>  
>  	return ret;
>  }
> @@ -1371,6 +1373,9 @@ static void adv7511_remove(struct i2c_client *i2c)
>  {
>  	struct adv7511 *adv7511 = i2c_get_clientdata(i2c);
>  
> +	if (adv7511->host_node)
> +		of_node_put(adv7511->host_node);
> +
>  	adv7511_uninit_regulators(adv7511);
>  
>  	drm_bridge_remove(&adv7511->bridge);
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7533.c b/drivers/gpu/drm/bridge/adv7511/adv7533.c
> index 4481489aaf5e..5f195e91b3e6 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7533.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7533.c
> @@ -181,8 +181,6 @@ int adv7533_parse_dt(struct device_node *np, struct adv7511 *adv)
>  	if (!adv->host_node)
>  		return -ENODEV;
>  
> -	of_node_put(adv->host_node);
> -
>  	adv->use_timing_gen = !of_property_read_bool(np,
>  						"adi,disable-timing-generator");
>  

-- 
Regards,

Laurent Pinchart