Hi Laurent,

Thanks for the feedback.

-----Original Message----- From: dri-devel dri-devel-bounces@lists.freedesktop.org On Behalf Of Laurent Pinchart Sent: 16 November 2024 15:32 Subject: Re: [PATCH v4 1/3] drm: adv7511: Fix use-after-free in adv7533_attach_dsi()

Hi Biju,

Thank you for the patch.

On Sat, Nov 16, 2024 at 12:54:10PM +0000, Biju Das wrote:

...

The host_node pointer was assigned and freed in adv7533_parse_dt(), and later, adv7533_attach_dsi() used the same. Fix this use-after-free issue with the below changes:

1. Drop host_node from struct adv7511 and instead use a local pointer in adv7511_probe().
2. Update adv7533_parse_dt() to return the host_node.
3. Pass the host_node as a parameter to adv7533_attach_dsi().
4. Call of_node_put() after use.

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 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.h | 6 +++--- drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 22 ++++++++++++++------ drivers/gpu/drm/bridge/adv7511/adv7533.c | 20 +++++++++--------- 3 files changed, 29 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511.h b/drivers/gpu/drm/bridge/adv7511/adv7511.h index ec0b7f3d889c..9f3fae7cc597 100644 --- a/drivers/gpu/drm/bridge/adv7511/adv7511.h +++ b/drivers/gpu/drm/bridge/adv7511/adv7511.h @@ -383,7 +383,6 @@ struct adv7511 { struct regulator_bulk_data *supplies;

/* ADV7533 DSI RX related params */

• struct device_node *host_node; struct mipi_dsi_device *dsi; u8 num_dsi_lanes; bool use_timing_gen;

@@ -417,8 +416,9 @@ enum drm_mode_status adv7533_mode_valid(struct adv7511 *adv, const struct drm_display_mode *mode); int adv7533_patch_registers(struct adv7511 *adv); int adv7533_patch_cec_registers(struct adv7511 *adv); -int adv7533_attach_dsi(struct adv7511 *adv); -int adv7533_parse_dt(struct device_node *np, struct adv7511 *adv); +int adv7533_attach_dsi(struct adv7511 *adv, struct device_node +*host_node); struct device_node *adv7533_parse_dt(struct device_node *np,

• 		     struct adv7511 *adv);
  
  

#ifdef CONFIG_DRM_I2C_ADV7511_AUDIO int adv7511_audio_init(struct device *dev, struct adv7511 *adv7511); diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c index eb5919b38263..3f1f309791a5 100644 --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c @@ -1209,6 +1209,7 @@ static int adv7511_parse_dt(struct device_node *np, static int adv7511_probe(struct i2c_client *i2c) { struct adv7511_link_config link_config;

• struct device_node *host_node = NULL; struct adv7511 *adv7511; struct device *dev = &i2c->dev; unsigned int val;

@@ -1233,12 +1234,17 @@ static int adv7511_probe(struct i2c_client *i2c) if (ret && ret != -ENODEV) return ret;

• if (adv7511->info->link_config)

• if (adv7511->info->link_config) { ret = adv7511_parse_dt(dev->of_node, &link_config);

• else

• ret = adv7533_parse_dt(dev->of_node, adv7511);
  

• if (ret)

• return ret;
  

• if (ret)
  

• 	return ret;
  

• }

• if (adv7511->info->has_dsi) {

• host_node = adv7533_parse_dt(dev->of_node, adv7511);
  

• if (IS_ERR(host_node))
  

• 	return PTR_ERR(host_node);
  

• }

  ret = adv7511_init_regulators(adv7511); if (ret)

host_node is leaked here.

Oops. Missed it.

...

@@ -1343,9 +1349,11 @@ static int adv7511_probe(struct i2c_client *i2c) }

if (adv7511->info->has_dsi) {

• ret = adv7533_attach_dsi(adv7511);
  

• ret = adv7533_attach_dsi(adv7511, host_node);
  

  if (ret) goto err_unregister_audio;

• of_node_put(host_node);
  

  }

  return 0;

@@ -1362,6 +1370,8 @@ static int adv7511_probe(struct i2c_client *i2c) err_i2c_unregister_edid: i2c_unregister_device(adv7511->i2c_edid); uninit_regulators:

• if (host_node)

• of_node_put(host_node);
  

The error label and the error handling code are now out of sync, making the code harder to read and more error-prone.

Error handling is why I proposed keeping of_node in the adv7511 structure, and calling of_node_put() in adv7511_remove() and at the end of the error handling path in adv7511_probe().

OK got it, Then will keep the of_node in the adv7511 structure to make the error label and error handling code in sync.

Cheers, Biju

...

adv7511_uninit_regulators(adv7511);

return ret; diff --git a/drivers/gpu/drm/bridge/adv7511/adv7533.c b/drivers/gpu/drm/bridge/adv7511/adv7533.c index 4481489aaf5e..5d0e55ef4028 100644 --- a/drivers/gpu/drm/bridge/adv7511/adv7533.c +++ b/drivers/gpu/drm/bridge/adv7511/adv7533.c @@ -131,7 +131,7 @@ int adv7533_patch_cec_registers(struct adv7511 *adv) ARRAY_SIZE(adv7533_cec_fixed_registers)); }

-int adv7533_attach_dsi(struct adv7511 *adv) +int adv7533_attach_dsi(struct adv7511 *adv, struct device_node +*host_node) { struct device *dev = &adv->i2c_main->dev; struct mipi_dsi_host *host; @@ -142,7 +142,7 @@ int adv7533_attach_dsi(struct adv7511 *adv) .node = NULL, };

• host = of_find_mipi_dsi_host_by_node(adv->host_node);

• host = of_find_mipi_dsi_host_by_node(host_node); if (!host) return dev_err_probe(dev, -EPROBE_DEFER, "failed to find dsi host\n"); @@ -166,22 +166,22 @@ int

adv7533_attach_dsi(struct adv7511 *adv) return 0; }

-int adv7533_parse_dt(struct device_node *np, struct adv7511 *adv) +struct device_node *adv7533_parse_dt(struct device_node *np,

• 		     struct adv7511 *adv)
  

{

• struct device_node *host_node; u32 num_lanes;

  of_property_read_u32(np, "adi,dsi-lanes", &num_lanes);

  if (num_lanes < 1 || num_lanes > 4)

• return -EINVAL;
  

• return ERR_PTR(-EINVAL);
  
  

  adv->num_dsi_lanes = num_lanes;

• adv->host_node = of_graph_get_remote_node(np, 0, 0);
• if (!adv->host_node)

• return -ENODEV;
  

• of_node_put(adv->host_node);

• host_node = of_graph_get_remote_node(np, 0, 0);

• if (!host_node)

• return ERR_PTR(-ENODEV);
  
  

  adv->use_timing_gen = !of_property_read_bool(np, "adi,disable-timing-generator"); @@ -190,5 +190,5 @@ int

adv7533_parse_dt(struct device_node *np, struct adv7511 *adv) adv->rgb = true; adv->embedded_sync = false;

• return 0;

• return host_node;

}

-- Regards,

Laurent Pinchart