[PATCH] drm: Set dev->registered back to false in case of register failure

[Krzysztof Niemiec <krzysztof.niemiec@intel.com>]

The dev->registered variable was initially added in such a way that it
is only set after all functions that could have failed have been called
and haven't returned an error. However, since then, the function
drm_modeset_register_all() is being checked for its return value, which
opens a possibility of failing the register after setting the registered
variable anyway. drm_dev_register() cleans up after itself in case of
failure, mimicking the functions called in drm_dev_unregister(), with
the exception of drm_client_sysrq_unregister() and
drm_panic_unregister() (_register() counterparts of which are not
checked for their return values), and the dev->registered flag.

This creates a situation in which after calling drm_dev_register()
nothing is registered (as the function entered an error path and cleaned
up), but the device is reported as being registered according to the
dev->registered variable.

This, for example, confuses the WARN_ON() in drm_mode_object_register(), which
is raised if a non-dynamic mode object is attempted to be unregistered
in between the drm_dev_register() and drm_dev_unregister() calls. If
drm_dev_register() fails - meaning the device *isn't* registered -
currently it still reports dev->registered = true, which triggers the
WARN_ON(), even though the usage is correct in that instance.

Set dev->registered back to false in the error path to prevent this.

Signed-off-by: Krzysztof Niemiec <krzysztof.niemiec@intel.com>
---
 drivers/gpu/drm/drm_drv.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 985c283cf59f..92403d79bb64 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -1116,6 +1116,7 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
 	if (dev->driver->unload)
 		dev->driver->unload(dev);
 err_minors:
+	dev->registered = false;
 	remove_compat_control_link(dev);
 	drm_minor_unregister(dev, DRM_MINOR_ACCEL);
 	drm_minor_unregister(dev, DRM_MINOR_PRIMARY);
-- 
2.45.2