The patch below does not apply to the 4.20-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 4d80273976bf880c4bed9359b8f2d45663140c86 Mon Sep 17 00:00:00 2001
From: Lyude Paul lyude@redhat.com Date: Mon, 8 Oct 2018 19:24:30 -0400 Subject: [PATCH] drm/atomic_helper: Disallow new modesets on unregistered connectors
With the exception of modesets which would switch the DPMS state of a connector from on to off, we want to make sure that we disallow all modesets which would result in enabling a new monitor or a new mode configuration on a monitor if the connector for the display in question is no longer registered. This allows us to stop userspace from trying to enable new displays on connectors for an MST topology that were just removed from the system, without preventing userspace from disabling DPMS on those connectors.
Changes since v5: - Fix typo in comment, nothing else
Signed-off-by: Lyude Paul lyude@redhat.com Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch Cc: stable@vger.kernel.org Link: https://patchwork.freedesktop.org/patch/msgid/20181008232437.5571-2-lyude@re...
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c index 3cf1aa132778..c1a35078b2b9 100644 --- a/drivers/gpu/drm/drm_atomic_helper.c +++ b/drivers/gpu/drm/drm_atomic_helper.c @@ -308,6 +308,26 @@ update_connector_routing(struct drm_atomic_state *state, return 0; }
+ crtc_state = drm_atomic_get_new_crtc_state(state, + new_connector_state->crtc); + /* + * For compatibility with legacy users, we want to make sure that + * we allow DPMS On->Off modesets on unregistered connectors. Modesets + * which would result in anything else must be considered invalid, to + * avoid turning on new displays on dead connectors. + * + * Since the connector can be unregistered at any point during an + * atomic check or commit, this is racy. But that's OK: all we care + * about is ensuring that userspace can't do anything but shut off the + * display on a connector that was destroyed after its been notified, + * not before. + */ + if (!READ_ONCE(connector->registered) && crtc_state->active) { + DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] is not registered\n", + connector->base.id, connector->name); + return -EINVAL; + } + funcs = connector->helper_private;
if (funcs->atomic_best_encoder) @@ -352,7 +372,6 @@ update_connector_routing(struct drm_atomic_state *state,
set_best_encoder(state, new_connector_state, new_encoder);
- crtc_state = drm_atomic_get_new_crtc_state(state, new_connector_state->crtc); crtc_state->connectors_changed = true;
DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] using [ENCODER:%d:%s] on [CRTC:%d:%s]\n",