linux-kernel - [PATCH AUTOSEL 5.15 10/25] drm: hide unregistered connectors from GETCONNECTOR IOCTL

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Date:   Sun,  9 Oct 2022 19:54:10 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Simon Ser <contact@...rsion.fr>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Jani Nikula <jani.nikula@...el.com>,
        Lyude Paul <lyude@...hat.com>, Sasha Levin <sashal@...nel.org>,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.15 10/25] drm: hide unregistered connectors from GETCONNECTOR IOCTL

From: Simon Ser <contact@...rsion.fr>

[ Upstream commit 981f09295687f856d5345e19c7084aca481c1395 ]

When registering a connector, the kernel sends a hotplug uevent in
drm_connector_register(). When unregistering a connector, drivers
are expected to send a uevent as well. However, user-space has no way
to figure out that the connector isn't registered anymore: it'll still
be reported in GETCONNECTOR IOCTLs.

The documentation for DRM_CONNECTOR_UNREGISTERED states:

> The connector […] has since been unregistered and removed from
> userspace, or the connector was unregistered before it had a chance
> to be exposed to userspace

Signed-off-by: Simon Ser <contact@...rsion.fr>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc: Jani Nikula <jani.nikula@...el.com>
Reviewed-by: Lyude Paul <lyude@...hat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220801133754.461037-1-contact@emersion.fr
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/drm_mode_config.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index 37b4b9f0e468..6a326b41d193 100644
--- a/drivers/gpu/drm/drm_mode_config.c
+++ b/drivers/gpu/drm/drm_mode_config.c
@@ -150,6 +150,9 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
 	count = 0;
 	connector_id = u64_to_user_ptr(card_res->connector_id_ptr);
 	drm_for_each_connector_iter(connector, &conn_iter) {
+		if (connector->registration_state != DRM_CONNECTOR_REGISTERED)
+			continue;
+
 		/* only expose writeback connectors if userspace understands them */
 		if (!file_priv->writeback_connectors &&
 		    (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK))
-- 
2.35.1