drm: fix race between partial drm_dev_register() failure and ioctl

If drm_dev_register() fails after registering a minor (e.g. render minor
registered, primary minor fails), userspace could have opened the first
minor and entered a drm_dev_enter() critical section. Since the
unplugged flag was never set, the ioctl proceeds while the error path
tears down device resources.

Fix this by introducing drm_dev_synchronize_unplug(), which sets the
unplugged flag and waits for the SRCU barrier, ensuring all in-flight
drm_dev_enter() critical sections complete before cleanup proceeds; call
it on the error path of drm_dev_register().

Fixes: bee330f3d672 ("drm: Use srcu to protect drm_device.unplugged")
Cc: stable@vger.kernel.org
Reported-by: sashiko-bot@kernel.org
Closes: https://lore.kernel.org/all/20260620190648.2E9F61F000E9@smtp.kernel.org/
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-17-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

0 files changed, 0 insertions, 0 deletions